Sunday, December 27, 2009
Some time ago I wrote about the Haematococcus algae I discovered in a puddle in my garden. At the time I enthused about the book Freshwater Microscopy by W.J. Garnett, a guide from another era for the amateur to culturing and identifying pond life. Inspired by the book I recently revisited my puddle and was well rewarded with a number of tiny critters new for me. Photo 1 (click to enlarge) shows three : a) A ciliate (more below) b) what I think may be a cyanobacterium and c) another ciliate that I think may be a paramecium. (As always my identifications come with a health warning. I'm happy to have them corrected).
Photo 2 shows a closeup of 'a' taken at 1000x magnification using my microscope's oil-immersion lens. Features to note about my organism are its large nucleus and the numerous swimming hairs (cilia) covering its body.
Those interested in such arcane matters (those not may like to skip this paragraph) may like to know the specimen here was stained with ~0.01% aqueous Eosin dye then mounted in a mix of water and glycerin with a little added disinfectant (to prevent future growth of mould). In an attempt to render the slide permanent I adopted the 'double cover slip method' . There's a detailed explanation of this here but briefly it involves sandwiching the specimen in its aqueous mountant between two differently sized coverslips, then mounting this sandwich in turn in a solvent based mountant (Permount in my case) thereby sealing in the aqueous mountant against evaporation and hopefully rendering the whole arrangement permanent. (Since acquiring my hobbyists microscope a couple of years ago I've developed a growing passion for making up microscope slides!)
Returning to my specimen itself, I have a couple of basic photoguides to pondlife and from images in these, and the general size (~40um) and form of my ciliate, I was tempted to identify it as a species in the genus Colpidium. You can find some stunning photo's of this and other protozoa here. From the volume of images on the web this seems to be a not uncommon find in pondwater. Unfortunately however, having looked at the equally splendid Protist Images website I'm no longer so confident. The problem is that the phylum Ciliphora (=little organisms like mine with cilia) is broken down into such a large number of superficially similar genera that it's hard for the amateur like me to know that my wee beastie is definitely a Colpidium and not say, a member of the catchily entitled Trithigmostoma, or the Drepanomonas, or the Cinetochilium...or for that matter the Tetrahymena I hear you cry! The Protist Database does give some guidelines for discriminating amongst these genera - typically discrimination involves carefully noting the position of mouth parts, the presence/absence of any stiffer bristles amongst the more whiskery cilia, or the absence of cilia on some parts of the body - but I confess I've not attempted to apply these to my organism since, firstly, the time commitment, my limited number of specimens and my comparatively humble microscope setup would, I'm sure, limit my chances of a successful identification. Secondly, there exists a nagging worry at the back of my mind that the taxonomy ('family tree') of the protozoa may not in fact be correctly established at this time. Certainly, the arrival of DNA sequencing technology is requiring that large amounts of what was assumed to be true about the inter-relationships of different species in other fields of biology is having to be drastically revised. The problem is that what two species look like is not necessarily a guide to how closely related they really are. DNA testing is revealing that superficially similar organisms can sometimes be only distantly related. The opposite is also true. I wrote about this in detail in my previous posting on the Glistening Inkcap Coprinus mushroom. I have no knowledge of the true status for microscopic cilates but I would not be at all surprised to learn that their taxonomy is also undergoing something of an upheaval amongst the professionals. For this reason also I've not attempted a more detailed identification of my ciliate. Of course, my thinking on all this may be entirely wrong. Perhaps someone looking at my photo's can tell immediately what species I have. If so, and you're that person, do please leave a comment.
Friday, December 25, 2009
And what better way to enjoy the day than with a photo of one of my favourite visitors to the British garden: the Fieldfare (Turdus pilaris). Photos 1 and 2 show rear and front views (captured using my home-made camera trap incidentally).
I have an apple tree in my garden, which, besides providing a home for various lichens and mosses (not to mention a resting post for beeflies!) yields a bumper crop of cooking apples. So many in fact that that I have given up trying to collect them all and lots are left to lie on my lawn where they fall. They may look a bit untidy but this is more than made up for by the large numbers of Blackbirds, Fieldfares, Song Thrushes and other birds they attract come winter. In my garden, it is not unusual to find fifty birds at a time feeding upon them .
At 26cm in length and 100g, Fieldfares are a little larger and stockier than Song Thrushes (the BTO site has a host of biometric data). They eat invertebrates and berries (and apples!).
Fieldfares are not really resident in Britain. I say 'not really' since, as I learn from my copy of the RSPB Handbook (Holden and Cleeves) in fact a first British breeding pair was recorded here in the Orkney Isles in 1967. Over subsequent decades the number climbed to a peak of 13, but has since fallen back to less than five pairs a year. Of the population of one million individuals in Britain and Ireland, the overwhelming number are winter migrants, arriving here from late October from Scandinavia and Northern Russia.
Attempting to learn something further about Fieldfares I did a quick internet search and came across an interesting online paper by O. Hogstadt Nest Defence Strategies in the Fieldfare (Ardea 92(1), 79-84) in which the author reports studies of the response of nesting Fieldfares to effigies of crows and stoats - common egg predators of the Fieldfare. The Fieldfare's under study showed a distinct and rather well optimised reaction to these two predators. With crows, the reaction was to try to deter the attackers by defecating on them. This makes sense as fecal matter would certainly be detrimental to the performance of a crow's feathers. With stoats however, the reaction of the Fieldfares was to silently slip away from the nest and delay their return - eminently sensible when faced with a predator that hunts mainly by smell and is an equal danger to eggs and adults alike.
To end why not a few lines of poetry. These from the Cornthwaite by the British poet, Norman Nicholson (1914-1987):
Granite and black pines, where the migrant fieldfare breeds
And the ungregarious, one-flowered cloudberry
Is commoner than the crowding bramble.
Saturday, December 12, 2009
Photo 1 shows a small troop of mushrooms I found growing in some damp grass beneath my garden hedge.
From its general appearance my first thought was that these were a type of ink cap mushroom (see my previous posting here), but after watching them for a week there was no sign of any of the caps dissolving into an inky mess and it was clear further investigation would be needed.
The first thing to do when seeking to identify a mushroom is to take a spore print. This is extremely easy: place a cap, gills down, on any suitable surface, wait twenty minutes, remove, and hey presto - a spore print. That of my mushroom is shown in photo 2. Knowing spore colour (here, black) will typically allow you to rule out at least half the species in the average mushroom guide.
If you have a microscope it can also be valuable to ascertain spore shape and size. Mine were ovoid and around 12x6micron (photo 3).
Other features I noted for my mushroom were the the grooved (the technical term being striate) mostly brown cap, fading to white at the edge, and the 'flakey stem' (a.k.a. floccose stipe) in photo 1.
With these features in mind it was time to turn to the guide books. Unfortunately, such is the number of species of mushroom in Britain (more than 3000, with others, new to these shores, being recorded regularly) that no single guide book can cover them all. This proved the case for my mushroom. I failed to find it in the first three books I tried, the floccose stipe proving a rather troublesome feature, ruling out a number of otherwise similar small brown mushrooms in the books. It wasn't until I turned to my copy of Mushrooms and Toadstools (Cortecuisse and Duhem) that I found a picture of Psathyrella lutesnsis. All the features were there and I'm fairly confident in this indentification.
Cortecuisse describes P. lutensis as growing on damp ground (a fit with my location) and being scare-to-rare.
I have learnt in the course of writing this blog that almost any life form I come across will have some unique and curious aspect to its lifestyle (for example, its relationships with other creatures, its chemistry, or its means of reproduction). No doubt this is true of P.lutensis. Unfortunately my searches have failed to turn up any information about it whatsoever. Perhaps I have merely looked in the wrong places. On the other hand, so sporadic and fleeting may be its appearance that perhaps no one has ever studied my enigmatic little mushroom. If anyone knows more any more about it than merely its name, do please leave a comment.
Saturday, November 21, 2009
I have a Gooseberry bush in my garden. In previous years I've had a good berry crop. But not this year! In May something attacked the bush, totally stripping the leaves. The culprit is shown in photo 1.
From closely similar photo's on the web I'm fairly confident this is the larva of the Gooseberry sawfly (Nematus ribesii). I should add my customary 'health warning' however: I'm not an expert on plant pests. As an amateur, you quickly learn that in natural history, identification of insects (fungi, spiders, lichen etc. etc.) solely on the basis of a photograph is always risky. There are more than a dozen species in the Nematus genus for example (see Bioimages site). I've found photos of only a handful. My caterpillar certainly looks like N.ribesii, but I don't know for certain it isn't one of the others. Can anyone more expert comment?
The damage done to my poor Gooseberry bush is shown in Photo 2. The branches would normally have been covered in leaves at this point in the year.
I did not spot any adult N. ribesii. From the photo's on Faroe Nature however it would appear they are squat, orange insects. This site has a drawing of the wing veinature taken from the book 'The Wings of Insects' (J.H. Comstock, 1918). (Wing veins are an important guide to insect identification - see my posting here).
In searching for articles on my sawfly I came across the admirable site of the Journal of Cell Science. This carries a large, searchable database of freely downloadable scientific papers. My searches turned up three on gooseberry sawflies (L. Doncaster, 1907, L. Doncaster 1905 and S. Shafiq, 1954). All get rather technical in places and I don't pretend to have followed all the details. From a quick read however, an interesting snippet I picked up is that eggs from both fertilised and unfertilised N. ribesii females can hatch but that larvae hatching from unfertilised eggs are overwhelmingly male. Eggs are laid in rows on the lower side of leaves at intervals of about a minute incidentally.
The main topic of the papers above relates to embryogensis i.e. the truly miraculous feat that Mother Nature manages of beginning with a single cell (an egg) and by a processes of repeated cell-replication and inter-cell communication constructs a complete insect (say) comprising hundreds-of-thousands of cells of countless types, all located in the right places, and all in an incredibly short period of time (about 4 days in the case of N. ribesii). Trying to undestand how she does this remains one of the great challenges for modern bioscience. It is perhaps fitting for this posting, that one of the most intensely studied creatures in all of science is a fruit fly (Drosophila melanogaster), flies being an ideal test-animal for such studies (along with nematode worms - see my post here) since dozens can be kept in a test tube where they will breed copiously and the offspring hatch rapidly. Armies of biologists have published innumerable articles about D. melanogaster - this site gives a flavour.
So there you have it, a seemingly humble garden pest with a rich natural history. Mind you, it might have been nice to have had a gooseberry crumble this year!
Tuesday, October 13, 2009
On a whim, I recently got out my trusty Baermann funnel (which sounds far more technical than it actually is, namely, a sieve for sieving tiny critters out of soil) and was pleased to discover a host of new-for-my-blog creatures in a handful of old grass clippings. One, a mite, is shown in Photo 1 (click on photo's to enlarge)
Readers of my blog will know I make some effort to research the species of any creature I find in my garden. In the case of my mite however, this turned out to be no small challenge. Before this posting I knew nothing about mites. As I discovered, there are at least three factors mitigating against the amateur seeking to identify one to species level.
Firstly, there is the obvious minute size of mites' physical features. Identification to species can depend on close examination of some minute gland on the body or joint in the jaw-parts ('chelicerae'). With only one specimen and the type of microscope equipment typically available to the amateur, such features can be a challenge to view. The professional may perhaps turn to an extensive university collection of carefully dissected and permanently mounted specimens or examine their find by electron microscope. Sadly however, I don't have a electron microscope in my garden shed (I'm open to donations!).
A second challenge is the sheer number of mite species. More than 45,000 (here) have been recorded and some sources estimate this may be only 5% of the number awaiting discovery. To make matters worse there seems to be a dearth of elementary texts or online keys in the area. A number of advanced texts are available (at suitably advanced cost!) but there seems to be little along the lines of a field guide aimed at the amateur (I'd be pleased to be corrected on this matter).
Attempting to work through academic journal papers and keys brings one to a third difficulty, namely the dense jargon that accompanies the study of mites (acarology). The amateur must wrestle with references to such arcane structures as pretarsal condylophores, filiform corniculae and Claperede's organs. To complicate matters still further, acaralogists refer to the hairs (setae) that decorate mites' bodies in code ('h1', 'pg3' etc.) and not only does there seem to be no simple online explanation of how this code works (anyone?) but there is more than one system in use amongst the professionals.
Thankfully however, there are some notable exceptions to the comments above. On his excellent web site David Walter Evans has put together a Glossary of Acarine Terms, indispensable for making sense of the jargon of acarology. For discussion of some current research topics in acarology and some superb images see Macromite's blog. My searches turned up very few online keys but notable exceptions are the one on David Evans' site above and the interactive key here on the site of the North American Bee-Associated Mites project.
It was the latter that enabled me to make some progress with my mite. I spent some time inputting various features into the key with limited success, but then noticed my mite had 'brush like arthropodrial processes on the chelicerae' (in English: a fringe of hairs on its pincer-like mouthparts). You can see these in photo 2. In the key above this immediately narrows things down from my mite being in any of 36 possible families, to it being in the single family macrochelidae. (As always my identifications come with a health warning - I'm happy for them to be corrected)
Unfortunately that is as far as the key takes me and from the webpages of Dr G.W. Krantz I learn there are still well over a hundred individual species in the macrochelidae family. The book to consult would appear to be A Review of the Macrochelidae of the British Isles by Hyatt and Emberson, but this is out of print and seems generally unavailable.
In the course of my searches I pleased to discover that I am not the only UK amateur taking an interest in the fauna beneath our feet. Over at Alan Hadly's splendid site he too is busy studying macrochelidae mites (together with a host of other critters).
I must end this posting here. My intention in writing my blog is to learn something of the natural history of the creatures I encounter. It may not have escaped the attention of the observant reader however, that in this article I have largely failed to say anything about the natural history of mites. I feel relaxed! With 44,999+ species potentially still at large in my garden, I suspect this will not be the last time I have an opportunity to study these tiny creatures...
Sunday, October 4, 2009
I've previously blogged the nettles (Dioica urticae) growing in my garden (indeed, I guess some of you reading this may even now be tucked up in your nettle bed sheets!) and also described some of the capsid bugs (Liocoris tripustulatis) I found living on them.
Recently I've noticed evidence of a second lifeform feeding off my nettles, namely the galls in photo 1.
I am fortunate enough to be in possession of a set of a dozen-or-so volumes of Field Studies, a journal that was at one time published by the Field Studies Council. This admirable UK charity runs a wide range of residential study courses aimed at the amateur naturalist. The Field Studies journal is no longer printed which is a pity as it commonly used to feature keys for the amateur wanting to identify some of the trickier plants and animal in our fields and gardens, including (for present purposes) a key to British Plant Galls by Redfern, Shirley and Bloxham in the October 2002 issue. Fortunately, for those of you without old copies of the journal to hand, this key has been reprinted. You can purchase a copy along with various other gall guides from the British Plant Gall society here.
Redfern, Shirely and Bloxham list five arthropods and one fungal rust capable of causing galls on British nettles. The pouch-like swellings with slit-like grooves in their surfaces on the leaf in photo 1 indicate these are galls caused by the small fly, Dasineura urticae. Had I cut open some of the galls (I didn't) I might have been lucky enough to find some of the white grubs of this fly. Indeed, as I learnt from the very nice 'A Nature Observer's Scrapbook' site, I might even have found some predatory grubs from another species, laid there to eat the Dasineura urticae grubs.
I'm very far from being an expert in diptera (flies). From the Bioimages site however it seems there are several dozen British species in the fly genus Dasineura. This site has pictures of the grubs and galls of some of them.
I have only found one description of an adult D.urticae fly: My copy of Insects on Nettles (Davis, Richmond Publishing) describes a "very small fly with long antenna. Under a microscope an antenna looks like a string of beads...". Unfortunately I haven't been able to find a photograph on the web, although the Bioimages site does carry a photo of another Dasineura species (D. sisymbrii) which I guess may be rather similar since it too has bead-like antenna.
Sadly, that is as much as I have managed to learn about my mysterious fly. How and when the adults mate, how a female locates a host patch of nettles, whether she lays eggs or live grubs, how long the grubs remain inside their gall... I can only guess at the answers to these and a host of other questions. Another garden study-project to add to my burgeoning list!
Saturday, October 3, 2009
What with photography, microscopy and literature searching, my self-imposed mission to catalogue my garden's life places lots of demands on my free-time. When I've a chance however I'm still making an effort to set out my home-made moth trap at night. I did so recently (on the 22nd August for the record) and it yielded a good haul of new species to add to my garden list, amongst them the attractive moth in photo 1.
My moth's common name is The Blood-Vein, for reasons that I imagine are obvious. It is a member of the large (several hundred species in the UK) geometridae family of moths, so called because of the caterpillars of these moths walk with a measuring (=hence 'geometer'), 'inch-worm'-like, gait.
From my copy of Moths of Great Britain and Ireland (Townsend and Lewington) I understand Blood Vein caterpillars feed on dock, sorrel, knotgrass and common orache. I've not been able to find a picture of one on the web (anyone?). Price, Goldstein and Smith studied the suitability of the Blood Vein for introduction into the States as a biological control agent against 'Mile a Minute' Weed (their paper is available here). (They found it was unsuitable)
Adult Blood Vein's are fairly common in Mid- and Southern Britain, but get rarer in the North.
The Blood Vein gets but a single mention in my copy of the excellent Moths (Michael Majerus). One might expect that such small and fragile creatures as moths might tend not to fly about in severe weather such as during heavy downpours. Surprisingly this seems not to be the case however: Majerus reports setting up a moth trap during a severe thunderstorm and trapping several hundred moths, undaunted by the driving rain, within hours. A dozen or so Blood Veins were among them.
The Blood Vein's scientific name is Timandra comae. There seems to be some confusion over the the relationship between this moth and the closely similar Timandra griseata. At various times the two have been lumped together as a single species, and at other times split out as two. Current work suggests they are indeed two separate species.
In Greek mythology Timandra was one of the daughters of the Spartan King Tyndareus and his wife Leda (she of swan-fame). Timandra's sister was Helen of Troy. King Tyndareus managed to upset the goddess Aphrodite and was punished with a curse that all his daughters would be adulteresses. Daughter Timandra duly obliged, eventually marrying one King Echemus only to later desert him for King Phyleus.
Now, whether in fact my moth has a particularly adulteress streak to its nature I really can't say. Indeed, aside from the snippets of information above, I've been failed to find any significant written accounts of the biology and behaviour of The Blood Vein. Whether this is because I've not looked in the right places, or whether it is that The Blood Vein, in common with so many other insect species, has simply not been studied in detail, I do not know. I'd be delighted to find out a little more about this pretty moth however, so do leave a comment if you can help.
Monday, September 28, 2009
Readers of my blog may recall that some time ago I decided to investigate the microscopic inhabitants of some rainwater that had collected in my garden. I was delighted at the time to discover some mobile little Haematoccus algae. Spurred on by this success I recently decided to revisit a similar puddle.
This time the water was in shade and contained quantities of decaying leaf-matter. Placing a few drops under my micro- scope I saw nothing at first, but then began to notice numerous small, semi-transparent, stalked objects, such as those above the number '3' in the microscope photo 1 (click to enlarge). My first guess was that these were some sort of fungal spores. Then one moved!
Zooming in (Photo 2) revealed an ovoid creature with a fringe of hairlike cilia at the front end. You can just about make out one poking out above '2.7' on the scale bar. These cilia were in constant motion and set up eddy currents in the water, drawing in small food particles as I watched.
The move- ments made by my creature were highly charac- teristic. Any small distur- bance (such as a tapping the micro- scope slide) caused the stalk supporting the 'head' to rapidly contract, jerking the head backwards in the blink of an eye and at the same time changing the head-shape from ovoid to compact and spherical. Gradually over a period of perhaps half-a-minute the stalk would re-extend and the head return to its original shape.
My creature had one further surprise in store: I was amusing myself tapping the slide and watching the response, when, as if grown tried of my irritating presence, one of my little creatures suddenly detached itself from it's stalk and swam away!
I'm in possession of a nice introductory, colour Guide to Microlife (Rainis and Russell, Grolier Publishing) and I was relatively quickly able to identify my lifeform as a ciliate, the cilophora being a large collection ('phylum') of microscopic animals belonging to the even larger collection of microscopic animals, the protists (to get an idea of just how large you might like to peruse the 81,000 (!) images on the Protist database.)
Fortunately, the structure and habits of my creature allowed for some further progress: the presence of a contractile stalk, the cilia around the mouth and the fact that my little critter was able to swim free of its stalk all point to it being a member of the smaller (though still sizeable) subclass of organisms the peritrichia (which I read is from the Greek, peri=near, trichia=hair).
Now, had I observed any 'stalks' with more than one 'head', that might have narrowed things down to my creature being in the genus Epistylis. I didn't (though of course absence of evidence isn't evidence of absence), which finally brings me to the (somewhat tentative) conclusion that my little creature is a member of the genus Vorticella. Unfortunatly that's as far as I've got. There are a more than a dozen species in this genus and which mine is I can't tell. I'll be happy if anyone out there can tell me.
Naturally, I'm not the first microscopist to observe Vorticella and a little web browsing led me to two very nice articles (here and here) for the amateur. The latter includes some excellent photos including some of Vorticella reproducing by asexual budding. From these and other sites I also learn that a free swimming Vorticella 'head' is termed a telotroch and the stalk is able to contract by virtue of a contractile bundle of threads within termed a moneme. A paper by Sotelo and Trujillo-Cenoz (available to download here) has some ultra-high magnification electron-microscope photos of this and also reveals that the moneme is responsible for the shape-change the head suffers when the stalk contracts.
On the subject of cilia a quick web search turned up numerous papers and articles. My intention was talk about some here, but since I've already gone on for some length in this posting, and since I'm certain to have another opportunity to discuss cilia in the future (so many microscopic creature have them), I'll leave the topic for now.
Instead I'll end with a photo of a free-swimming little animal I encoun- tered in the same sample of water. The ident- ification of this one defeated me. Am I looking at a free swimming Vorticella or is this something else? If you know do please leave a comment.
Saturday, September 26, 2009
Success in discovering the identity of some plant or animal is all about the careful and methodical observation of details. I've written this before, and had I only paid attention to my own dictum, I might avoided wasting half a morning recently getting thoroughly confused over the species of some grass growing in a corner of my garden!
Intrigued by a comment in a booklet Practical Microscopy (Eric Marson, Northern Biological Supplies) - a superb guide I cannot recommend too highly to any amateur interested in preparing their own high quality microscope slides - I had set out to examine some blades of grass under my microscope.
Venturing into my garden I came across the grass in photo 1. The long, seed bearing structure is technically termed a 'spike'. I picked a little and came back inside but before putting it under the microscope I decided to try identifying the species using my copy of Grasses (Fitter et.al. publ. Collins). Having only a few inches of specimen, it wasn't long before I was stuck however. I went back outside therefore, found my clump of grass and picked a little more. Embassingly foolish as it seems now, this went on for nearly an hour, with me traipsing back and forth, collecting a little more grass each time and returning inside only to find myself more confused than ever.
Finally, in exas- peration, I threw away my growing collection of tattered grass cuttings and started a fresh, and this time, methodical study. The result was the arrangement in photo 2 and the belated realisation I'd been collecting bits of two different grasses!
The two in question are Couch grass (Elymus repens) (photo 2, upper) and Perennial Ryegress (Lolium perenne). Laid out neatly in photo 2 the differences are obvious. I can say that it underlines the lesson that one cannot trust that causal glance at that seemingly undifferentiated clump of 'spike bearing' grass swaying in the breeze!
One difference between the two grasses in photo 2 is leaf size. In fact however, this is not an overly useful guide to species identification, as the size of the leaf baldes can vary with their position on the 'stalk' (culm) and other factors (soil quality etc.). Instead, amongst the most useful guides to a grass's species is the shape and size of the ligule, a small vestigial leaf-like structure the nestles between the culm and a leaf. Photo 3 shows the ligule of Perennial Ryegrass. By contrast, Couch grass lacks a ligule (though just to confuse the unwary, the leaves wrap around the culm via two little sheath-like flaps know as auricles - see photo 4).
Returning to the spikes of my two grasses, photo 5 shows a closeup of both. These bear the grasses' minute flowers (the source of all that hayfever-inducing pollen in summer). As I learnt in my previous study of the Cultivated Oat (Avena sativa), the structure of grass flowers comes with a lot of botanical jargon. I'll not repeat it here, but for completeness I've labelled up photo's 6 and 7.
And what of that micro scope image I originally set out to acquire? Well, as everyone knows you can get a painful cut from the edge of a blade of grass. Putting one under the micro scope (photo 8) shows just why: a margin decorated with a row of tiny saw-toothed daggers. Another of nature's tiny miracles.
Saturday, September 19, 2009
Not everyone's favourite insect it must be admitted, photo 1 shows two wasps feeding on a rotten apple on my lawn (a habit shared with the mucor moulds I blogged previously).
The species here is the Common Wasp (Yellowjacket to those of you reading in the States) Vespula vulgaris, one of eight British species in the Vespidae family of social wasps. The hornet I blogged previously is another.
A number of the British social wasps are superficially rather similar and it can pay to take a close look at the face (photo 2) to be confident of the species. Were my wasp to be the not-uncommon German Wasp (Vespula germanica), for example, then it would have three little black dots in the centre of its face (mine doesn't). You can find a nice set of photos of the various British Vespidae species here.
Photo 2 also reveals my wasp is female: Her antennae have 12 segments (males have 13).
Wasps have been very common in my garden in recent summers and this is no doubt partly explained by the impressive abandoned nest (photo 3) I found in attic last winter.
Wasps have two pairs of wings, with each pair comprising a larger- and smaller wing. A pair gets 'zipped' together when the wasp lands so that it appears to be only a single wing. You can see this in photo 1. Taking one of the smaller wings and putting it under the microscope reveals that the analogy to a zip is well chosen: a row of hooks lines the edge of the smaller wing, allowing it to hook tightly onto the larger. Personally I never tire of looking at structures like this under the microscope. Any engineer will tell you how enormously demanding it is to machine mechanical devices to micron accuracy, yet mother nature is routinely able to grow fantastically intricate structures out of such unpromising materials as chitin or cellulose.
My efforts to learn something about Common Wasps led me back to the subject of 'worker policing', which you may recall I touched on in my posting on hornets. Briefly, it turns out that female workers in the colonies of many types of social wasp, bee and ant permit only eggs from the queen to hatch. Eggs laid by female workers are removed from the colony by other workers before they hatch. To the evolutionary biologist, this begs the simple question 'why?'. What advantage does the colony gain by only tolerating the eggs of a single individual (the queen)? Many learned papers have been written on this subject and I wouldn't presume a detailed understanding of all the technicalities but in brief, I understand the reason relates to so called 'kin selection'. It turns out that as a female worker, you are more likely to be closely genetically related to a grub hatching from a queen's egg than you are to one from the egg of fellow worker. Maximising all individuals' relatedness to each other is therefore achieved by preferentially rearing the queen's eggs.
Now, all of the above is as I explained it in my hornet posting. Whilst I didn't doubt the explanation, what I'd struggled to do there was to understand for myself in simple terms precisely why workers relate more closely to the queen's egg than to those of their sisters. In preparing this posting however, I came across the commendably readable More Than Kin and Less Than Kind by Douglas W. Mock. The key information I'd been missing concerns the way in which genes are passed down the generations in these many insects. Firstly it turns out what whilst female wasps each carry two sets of chromosomes (making them 'diploid' - just like us), males carry only a single set (they're haploid). Secondly it transpires that queens in insect colonies that practise worker policing, typically mate with multiple males. The sperm from all the queen's male partners is mixed together and stored in a vessel inside her body known as the spermatheca until needed to fertilise an egg. Which male's sperm fertilises which egg is then random. Taking these two facts together (the haploid/dipoloid male/female divide and the queen's 'random polygamy'), and working through some relatively simple genetics (anyone who remembers Mendel's sweet peas from school biology lessons should follow it), its not too hard to follow the chain of logic that shows that as a female worker born to a queen, you'll have a closer genetic resemblance to eggs from your mother than you will to eggs from your sisters.
And finally, I learn from a paper by Landolt et.al. that a good way to attract Vespula vulgaris wasps is to fill a vessel with acetic acid and isobutanol... of course, alternatively you might simply try eating a sandwich in your garden in August!
Thursday, August 20, 2009
Photo 1, taken on a sunny day in recent July shows a butterfly I found resting on a post in my garden. A few minutes with a butterfly guide and there's no mistaking it as The Gatekeeper (Pyronia tithonus).
My Gatekeeper was very obliging and gave me oodles of time to fetch my camera and take photo's. I might have thought nothing of this, but then I came across a nice online study by Christopher Young of 516 butterflies visiting a UK garden over three seasons. P.tithonus 'stuck around' for the longest of all. Whether this is simple coincidence or whether it points to a behavioural trait of the Gatekeeper I've no idea (an unrecognised butterfly habit awaiting study?).
A second common name for the Gatekeeper is the Hedge Brown. For some reason I prefer the first, though I can't imagine how it originated (anyone?).
The Gatekeeper in photo 1 is a male as confirmed by the dusky patches towards the centre of the forewings. In preparing this posting I came across a number of websites declaring that these are a source of pheromones. I haven't managed to locate an authoritative account to confirm this however (anyone?).
The Gatekeeper is a member of the Nymphalidae family of butterflies that includes some 25 UK resident species, amongst them my previously blogged Peacock . An obvious feature of both are the 'eye' spots. My quotation marks are carefully chosen having come across an interesting article by Stevens et.al. As I learnt in researching my Peacock butterfly posting, many studies have shown that the conspicuous wing spots of certain butterflies have a valuable effect as anti-predator devices, acting to startle small birds about the seize the insect. It has been widely assumed that the reason for this is that, to the birds, the wingspots resemble the eyes of larger predators (hawks, owls etc.). The paper by Stevens et.al. casts doubt on this however since their ingenious test experiments imply that the most effective patterns are not necessarily those that most closely resemble the eyes of predators.
Caterpillars of the Gatekeeper eat grasses. You can find an image of one here.
Sadly, that is as much as I have managed to learn about the Gatekeeper. I should like to have read a 2001 paper by Conradt et.al. that my web searching tuned up. From the abstract, I understand the authors' studies to have shown that P.tithonus can detect and orient itself by landmarks up to 150m away (an impressive distance sensing range for a small insect I'm sure you'll agree). Sadly however, like so much internet information about the natural world, the details are viewable only by making a payment to a private publishing house. Not something I, as am amateur, am inclined to do. Alas therefore, my curiosity and yours, dear reader, must go unsatisfied!
Monday, August 17, 2009
Weeding out my shrubbery recently, I was pleased and surprised to come across a second example of a UK amphibian to add to the first (a common frog) I wrote about last year: specifically a rather large toad. Sadly, by the time I had raced to my house and returned with my camera my toad had disappeared. My luck was in however as a few minutes spent hunting through the undergrowth turned up a second: the little fellow in photo 1.
Britain has only two species of toad. One, the Natterjack (Epidalea calamita), is a rare and protected species. I have never knowingly seen one myself. Our second is the Common Toad. There are various ways to tell the two apart but the most useful from the point of view of photo 1 is the paratoid gland which I've marked with a 'p' in photo 1 (click to enlarge). The fact that this is rather regular and pronounced indicates that mine is a Common Toad (Bufo bufo).
What I've learnt about the Common Toad has been mostly through reading The British Amphibians and Reptiles (Malcolm Smith, Collins New Naturalist). With regard to diet, the book contains the amusing quote (attributed to Newman 1869) "[the food of the toad] seems to consist of all living things that are susceptible to being swallowed". Bees, ants, whole snails, moths and young snakes have all been recorded in the diet of the Common. In the case of some larger South American and African toad species even full grown live mice are taken.
It seems possible the first, larger toad I saw and the second smaller one were a female and male respectively. Male Common toads average 60-65mm. Females are typically 10-15mm longer.
Common toads can live a surprisingly long time. Forty years has been recorded in captivity. They hibernate on land in burrows from around mid-October until mid-March when they emerge to spawn. Spawning continues until around the end of April. As is well known, toad spawn forms long 'necklaces' in the water as opposed to the more amorphous blobs formed by frogspawn.
Finally, a word about the predators of the Common Toad. Crows, magpies, rats and snakes are all known to eat toads (some of the former tending to eat the innards, leaving behind the unpleasant tasting skin). Prize for most gruesome predator has to go to the greenbottle fly Lucilia bufonivora however. Having located a victim an adult bufonivora lays up to 100 eggs on its unfortunate victim's back or thighs. Some time later the eggs hatch and the emergent maggots immediately make their way up the toad's back and into its eyes and from there into the nasal cavity. Within a few days the toad is dead. The maggots devour the corpse before dropping off to pupate in the soil and emerge a week or so later as adults ready to repeat the cycle. For those with a strong stomach you can see a photo of an infected toad here.
Wednesday, July 29, 2009
No, despite appearances to the contrary, I have not gone away! My camera has been kept busy over summer snapping pictures of a host of interesting creatures in my garden and it's high time I resumed the task of writing about them.
Some weeks ago I was clearing away a patch of weeds bordering my vegetable patch and I came across a troop of the lovely little mushrooms seen in photo 1 (click to enlarge). They seemed to be growing on a lump of decaying wood.
A quick look in my mushroom guide and I'm fairly confident my mushroom is a Collared Parachute Marasmius rotula.
I say 'fairly confident' as Marasmius bulliardii is similar in appearance though I read it is typically somewhat smaller than rotula and grows on leaves . You can find pictures of both, plus various other species, on the splendid Bioimages site and a key to some 60+ Marasmius species on Michael Kuo's site.
Had I gone to the trouble of taking a spore print (see my previous posting here), and assuming my mushroom is indeed M.rotula, I'd have found the spore colour was white. Under the microscope the spores are 7-10um x 3-4um in size and elliptical.
Turning to my copy of the excellent Fungi (Spooner and Roberts, publ. Collins) a nice thing to learn about Marasmius mushrooms is that one of them is amongst the world's oldest toadstools. A Marasimus-like mushroom ('Archeomarasiumus liggetti') was found, trapped in a 90 million year old piece of amber, in New Jersey by one David Hibbett, a Harvard mycologist. The American Museum of Natural History webpage carries a photo and Hibbett's webpage includes a link to his 1997 paper on the discovery ('Fossil mushrooms from the Cretaceous and Miocene ambers and the evolution of homobasidiomycetes' ).
And finally, the exceptionally sharp eyed of you may have spotted a second life form in photo 1, namely the little reddish insect clinging to the cap in the centre. Photo 2 shows a close up of the little critter. Some remarkably complex relationships exists between fungi and insects. The grubs of certain woodwasps for example, though partial to chomping holes in trees, are only able to ingest wood that has been first rotted by a fungus. Adult woodwasps therefore carefully transport this fungus in special grooves on their body and introduce it the same hole as their offspring. My little insect in photo 2 has a superficially wasp-like look about him or her, but his or her true identity and whether he or she has any sort of relationship with my mushroom, or simply happened to be passing through when I took the photo, I have no idea. If anyone of the experts out there can offer any information do please leave a comment.
Saturday, April 4, 2009
Photo 1 shows two more moths I caught (for the record, on 26th March) in my recently- constructed moth trap.
I didn't know the species of either at first but from my copy of Moths (Waring, Townsend and Lewington, British Wildlife Publishing) it's clear I've found (left) a Common Quaker (Orthosia cerasi) and (right) a Hebrew Character (Orthosia gothica).
I should easily identify them in future: the two, kidney-shaped wing spots of the Common Quaker and the black shapes on the wings of the Hebrew Character are very characteristic.
The Hebrew Character gets its name from the resemblance of its black wing markings to the letters (characters) of the Hebrew alphabet.
I was puzzled by the origin of the name 'Common Quaker' but then came across an article from the Times newspaper 2003, describing an interview with the naturalist Peter Marran. It seems that many of the common names for British moths were made up by members of the The Aurelian Society - one of world's first entomological societies, established in London in the 1760's. According to the article, Quaker's of the time wore (quotes) "subfusc attire" (i.e. dusky or drab clothes). This inspired the naming of not one but three British moths: The Powdered -, The Twin Spot- and (our moth here) The Common Quaker.
Adult of both the Hebrew Character and the Common Quaker feed on the nectar from sallow catkins whilst their caterpillars will eat a range of plants including Oak, Birch and Hawthorn.
An interesting feature of the Hebrew Character I learnt from reading Michael Majerus' book Moths (The New Naturalist Library) is that it displays high latitude melanism; In Northern Scotland, a form of the Hebrew Character - specifically Orthosia gothica f. gothicina - is found that lacks the black colour to the 'Hebrew letters' on its wings. Some other moths, notably the Scalloped Hazel and the Ingrailed Clay, also shows a distinct form at high latitudes. Why? Because, high latitudes impose some unique selective pressures on the moths that live there: firstly there may be issues of thermal regulation (having dark or pale wings will effect how easily a moth heats up or cools down); secondly the low angle of the sun creates softer lighting conditions that may mean birds can more easily pick out camouflage patterns that might work well elsewhere; thirdly, at high latitude in summer the sun does not set - a challenge for the camouflage of normally night flying moths. Low latitude moths that want to 'make the transition' to high latitudes are therefore faced with the need to adapt their colourings or suffer the consequences. A wonderful example of evolutionary change.
Wednesday, April 1, 2009
Photos 1 and 2 (click to enlarge) show what must be the most dramatic 'nose' of any British fly.
A quick look through my copy of Michael Chinery's book Insects (Collins) and it appears that I've come upon a Bee Fly (Bombylius major). There are ten British species. B. major is the most commonly observed.
Bee Flies use their 'nose' (proboscis) to probe flowers for nectar. The length arises from their preference for hovering above, rather than actually landing on, flower heads. They do this presumably to avoid being ambushed by predators such as Crab Spiders that sometimes lurk behind flower petals.
Apparantly Bee Fly's are superb ariel acrobats. I didn't get a chance to observe this however since the one in the photo remained stubbornly perched on the branch of my garden apple tree. We'd had a few warm Spring days here in Oxforshire. On the day the photo was taken however it had turned cold and my Bee Fly was very sluggish (he/she was still on the same spot half an hour later).
I've not found a specialist UK site devoted to Bee Flies, but you can find a key to those of Canada here.
The best general description of Bee Fly natural history I've come across on the internet is that of Louise Kulzer. They have a complex life cycle. As above, adults feed on nectar. Their grubs are parasitic on solitary bees and wasps however. An adult Bee Fly lays it eggs near the burrow of a (true) bee and the grubs, once hatched, find their way into the nest and consume the food intended for the (true) bee larvae. Later, the Bee Fly grub undergoes a 'shape change' (hypermetamorphosis) into a carnivorous grub, and eats the (true) bee larvae.
That at least is a general description. Ideally I'd have liked to have found some more specific details about my species Bombylius major (What types of bee/wasp species it parasitises; How the Bee Flies tracks down a host-bee's nest etc.) but sadly there seem few descriptions on the web. I did find one other site that references a paper by one T.A. Chapman, specifically on the life history of B. major ...from 1878! (I haven't been able to find a copy)
My searches were not entirely in vain. I did come across the studies of Catherine Toft who has written about the ecology of Bee Flies in the Californian Desert, in particular observations on the foraging behaviour of two species. My amateur understandingof her work is as follows:
Back in the late 1960's, one T.W. Shoener argued that, other things being equal, females in nature should seek to maximise the time they spend feeding (on the assumption that taking in more energy through feeding translates into being able to produce more offspring). Males on the other hand should be 'time maximisers' i.e. beyond basic dietary needs, time spent feeding is in some sense 'wasted time' away from looking for, and breeding with, females. Dr Toft noted that two species of Bee Fly (Lorodotus pulchrissimus and L. miscellus) lent themselves very well to a study of this since the two species of fly live in an essentially identical environment, sharing the same desert habitat and even feeding on the same plant.
As it turned out, L.misecellus matched the Shoener prediction: females spent more of their days foraging than males. Males of L. pulchrissimus bucked the trend however. They spent exactly the same amount of time foraging as females. This is apparantly a feature they share with male moose! Although Dr.Toft offers some tentative explanations as to why this might be. The ultimate answer appears to await a deeper study however.
All of which suggests to me, that should you be an amateur naturalist reading this and searching for an amusing but scientifically useful 'project' to undertake in your neighbourhood this summer, you could do worse than to sit in a deckchair with a cold drink and a stop-watch, and time the foraging patterns of that little-known bug in your backgarden!
Saturday, March 28, 2009
Chomping its way through a fallen twig, photo 1 shows a collection of the 'candle wick-like' fruiting bodies of the Candlesnuff fugus Xylaria hypoxylon.
This fungus is very common here in the UK. Scan piles of logs or fallen branches and you're likely to spot it on almost any country walk.
In common with the holly leaf fungus I blogged recently, and the morel before that, X.hypoxylon is a member of the ascomycetae - a huge collection (phylum) of fungi that 'grow' their spores inside microscopic tubes called asci.
In the case of X. hypoxylon a couple of hunded asci are, in turn, packaged into a structure called a perithecium - basically a small 'pimple' with a hole in the top through which spores, once liberated from an ascus, escape. There's an excellent cross sectional microscope photograph of a perithecium of one on the mycolog site (it's a big webpage - the photo's about half way down).
To the eye, the perithecia of X.hypoxylon appear as tiny black pimples on the surface of the white 'candle wicks'. You can see some in photo 2. (Perithecia are common features of lichens also (see my post here).) Over time, the surface tends to become increasingly covered with these pimples (compare Photo 1 with Photo 3 taken about two weeks later) until finally the 'wick' ('compound ascoma') appears quite black. The resulting 'charred' look gives the name pyrenomycetes (from the Greek 'pyr' = fire) to the class of mushrooms of which X.hypoxylon is a member.
The definitive web site on the pyrenomycota is that of by J.D. Rodgers.
In fact the life cycle of X.hypoxylon is a little complex. The spores liberated by the pimply black perithecia are the result of sexual reproduction. X. hypoxylon is also able to reproduce asexually via so-called 'condiospores' however. These conidiospores give the fungus its white powdery appearance in photo 1.
Seen under the microscope, the sexual spores of different species of mushroom show characterisitic differences in size and shape (a helpful aid when trying to identify a mushroom - see my previous posting). I read on Michael Kuo's site however, that conidiospores from different fungi all look basically the same. Why nature has chosen to distinguish sexual and asexual spores in this fashion I can't imagine. Can anyone comment?
Tuesday, March 24, 2009
Spring is well and truly springing here in Oxfordshire. Soon animals and plants will be appearing in my garden faster than I can photograph them, let alone write about them. Whilst things are still moderately calm therefore, I'm seizing the moment to press on with my task of cataloguing my garden's lichens.
Quietly going about its business, photo 1 (click on photos to enlage) shows a black crustose lichen (for the uninitiated, see my explanation here) that decorates my garden wall in places. Photo 2 is a closeup (I've slightly digitally sharpened this image using software).
I'm no expert, and happy to be corrected, but from what I can tell from leafing through my copy of Lichens (Frank Doson), although there are numerous lichens with black fruiting bodies ('apothecia') on otherwise coloured 'backgrounds' ('thalli'), there are only a handful of mostly- or wholly-black crustose lichens to be found in Britain. A number are marine. Verrucaria maura, for example, is common on rocky shorelines where it is somtimes mistaken for oil pollution.
Of the mostly black, 'land-locked', lichens, I spent some time looking at the photos of Verrucaria nigrescens on the excellent 'UK Lichens' site. Looking closely however, this seems to have a more chocolate-brown thallus, albeit one peppered with many black 'perithecia' (see my definition here).
On balance therefore I'm tentatively identifying my lichen as Placynthium nigrum which my copy of Dobson describes as being "Very common, mainly on hard calcareous substrates throughout Britain. Often found on flat tombstones and cement".
A slight puzzle is that the photo in Dobson shows a more powdery ('coralloid') surface than is evident in my photo 2, although the book adds this lichen may be "sometimes smooth and cracked especially in polluted areas". Where I live is rural and I don't believe especially polluted. That said, some lichens are extraordinarily sensitive to even minute amounts of air pollution - whole books have been written on this topic. Anyhow this variability in texture gives me some added confidence in my identification.
Turning to my copy of Lichens (Oliver Gilbert, New Naturalist Library) a nice thing to discover was some growth-rate data for Placynthium nigrum. I learn that young patches expand their radius at 1.66mm/year and mature patches at 0.08mm/year. Lichenometry is the technique of dating old structures (churches, stone circles etc.) by studying their lichen populations - you can find an article here. Applying the data above to the approximately circular, 10mm-radius, patch in photo 2 ages my lichen at between 6- and 125-years old! Not the most exact figure I grant you, but fun to know.
As I commented in a recent posting, I am puzzled by the colours lichens adopt. Over the millenia animals have been driven to evolve their numerously-coloured fur coats, feathers and exoskeletons so as to optimally attract mates, hide from predators, advertise their venomous stings etc. Similarly my amateur's understanding is that plants are mostly green by virtue of the need to pack their leaves and stems with chlorophyll. Even various of the larger mushrooms have evolved specific colours, presumably to alert browsers to their poisonous nature or advertise their presence to 'pollinating' (botanists may wish to turn away at this point!) insects. Some even glow in the dark for this very purpose. But how it is that some lichens on my garden stonework gain advanatage by being coloured matt black, whilst others 'prefer' greyish/white and still others, bright yellow, I struggle to guess. Can anyone help?
Today's posting brings my garden lichen species-count to eight. I feels that I may be approaching completion with regard to this particular lifeform. Until, that is, I find another dozen species through more careful inspection of my garden's rocks and trees. Stood outside earlier today for example, when acquiring the photos above I was aware only of our black friend and of the grey-white patches which (though I haven't checked in detail) I'm assuming is our old friend Verrucaria. Sitting now at my computer screen however, staring at an enlarged version of the photo 1, I'm suddenly noticing the array of tiny orange blobs towards the centre of the image. Time to go back outside methinks!
Hot on the heels of one of my favourite garden birds, one of my favourite flowers: The Snowdrop (the photo was taken back in mid-February)
Snowdrops are members of the plant genus Galanthus (from the Greek 'gala'=milk, 'anthus' = flower). What I've learnt about them has been mostly through Mark Smyth's very nice Snowdropinfo website, the Royal Horticultural site, the BBC site, and from my trusty copy of The Englishman's Flora (Geoffrey Grigson).
Firstly, regarding the name, both the RHS site and Grigson state that 'Snowdrop' derives from the German word Schneetropfen, a type of ear ring popular in the 16th and 17th century. Now, whilst I'm entirely happy to accept this, neither author gives a reference without which it's not immediately obvious to me that likening this plant to a 16th century German earring is more likely than people having chosen the 'Snowdrop' after... er, well...drops of snow! (Anyone?)
Geoffrey Grigson lists other folk names including Eve's Tears and Candelmas Bells, the latter a reference to the Christian festival of February 2nd when Snowdrops are one of the few plants in flower.
According to the BBC's site, bringing Snowdrops into the house at Candelmas symbolises a death.
Snowdrops are widely spread across Europe and Asia. There are nineteen true species (there's a list on Wikipedia's Snowdrop page) and literally hundreds of artificial cultivars, with new ones created all the time by enthusiasts ("Galanthophiles"), and old varieties occasionally re-discovered in sleepy vicarage gardens or (see the National Trust site here) on overgrown Victorian rubbish dumps!
You can find a photo-gallery of cultivars on Mark Smyth's site. What characteristics elevate nineteen types of Snowdrop to true species level I'm not sure (anyone?). My copy of 'The Wildflower Key' (Francis Rose) lists only one for the UK - Galanthus nivalis.
The chemical Galantamine was first isolated from Snowdrops and today finds medical application in the treatment of Alzeimer's disease.
Finally a few words on Snowdrop pests and diseases, of which there are various: The RHS site describes the two fungi Botrytis galanthinae and Stagonospora curtisii as 'the bane of many snowdrop growers.' Snowdrops are also attacked by the larvae of the Swift Moth and the stem nematode worm (Ditylenchus dipsaci) (you can download a pdf file about the latter here). Prize for impressive pest has to go to the Narcissus fly (Merodon equestris) however. This black-and-yellow insect wards off predators by mimicking a Bumblebee. You can find some photo's at the insect images website. Painful as it will be to the ears of gardeners, and although I enjoy my garden's snowdrops far too much to want to see them all wiped out, as an amateur naturalist I have to say I wouldn't mind sacrificing just one or two bulbs for the chance to see one of these flies for myself!
Monday, March 23, 2009
I promise that shortly I will end my minor obsession with moth postings dear readers and return to describing some of my garden's other life. For now however, two more moths caught in my new home-built moth trap.
Photo 1 shows an Early Grey (Xylocampa areola), its wings camouflaged to help it hide on trees and, photo 2, a rather tired and tattered looking moth that I think may be a Dark Chestnut (Conistra ligula) though is possibly a Chestnut (Conistra vaccinii) (My identifications come with a ‘health warning’ - I’m no moth expert and happy to be corrected). You can find better photo's on the excellent UK Moth site.
Caterpillars of the Early Grey feed on Honeysuckle, and those of the Dark Chestnut on Willow and other plants.
I learn from my copy of Moths (Michael Majerus) that the Dark Chestnut is an unusually early egg-layer amongst British moths, usually laying in March.
Sadly, beyond the facts above, I’ve been able to find very little to say about the life-styles and behaviours of either of my moths. Of course, this may be because I’ve not searched enough. If there is one thing that I have learnt from writing this blog however, it won't be because there is nothing remarkable to discover about them. As I've discovered time and again during my researches, there is an almost inexhaustible subtly and complexity in nature.
Take for example, the two butterflies, The Grayling (Eumenis semele) and the European Silver Washed Fritillary (Argynnis paphia) -
In his semi-autobiographical Curious Naturalists, a wonderfully readable account of a life spent watching and recording behaviour in birds and insects, and one of my all-time favourite natural history books incidentally, the Nobel Prize winning biologist Niko Tinbergen described some of the 50,000(!) experiments he and his team performed to gain an understanding of the behaviour of the former butterfly.
During the breeding season, male Graylings are in the habit of chasing almost anything that flutters by in the hope it may be a female. Using equipment no more sophisticated than a fishing rod 'baited' with a series of cut-out paper shapes, Tinbergen was able to reveal such facts as i) Although male Graylings are sensitive to colour (they preferentially feed on blue and yellow flowers) surprisingly, when choosing to give chase, they don't care about the colour the object fluttering by ii) Nor are they the least concerned that the ‘flutterer’ should resemble a fellow butterfly – they will happily chase a fluttering paper rectangle iii) They do care about size however; If you’re a male Grayling seeking a mate then, within reason, the bigger she is the better!
This is only the start. Once a male finally meets a female, a rich and complex courtship ‘dance’ ensues with he performing acts such as wafting scent over his partner with his wings, and gently clasping her antennae between them.
Now, in her book, Courtship: A Zoological Study (publ. Heinemann), Dr. Margaret Bastock describes some similar studies (made by D. Magnus in the 1950's) into the breeding rituals of the Silver Fritillary. Again males will chase a variety of passing ‘fluttery things’, but this time males are choosy about colour -they like best to chase yellow things.
Two butterflies, two rich and complex behaviours with intriguing differences, both only ‘decoded’ by thousands of hours of patient observation. It makes me wonder what intricate shenanigans my two moths may be about in the dead of night. (Anyone?).
Even supposing more is known about my two moths however, with more than 850 larger moths in the UK alone, not to mention 250 hoverflies, more than 450 spiders, 3200 Ichneumenoid wasps…and let’s not even think about beetles (see here), it’s certain that only a tiny fraction of what goes on in the gardens, fields and forests on our doorsteps is known in any detail.
Personally I find it both an inspirational ‘call to arms’ to we amateur naturalists to get out our notebooks and our ‘paper butterfly' experiments, but also (if you’ll permit me a slightly gloomy ending to today’s posting) a little sad to think that in one’s lifetime there will never be enough time to observe even a small part of what there is.
Saturday, March 21, 2009
In my last posting I described my newly home-built moth trap. I’ve been operating it for only a week, and although we’re still in chilly-March here in Oxfordshire in the U.K., I’ve already ‘discovered’ a further half dozen species to add to the seventy-five living things I’ve already reported on this blog. Normally I give each species its own posting. I’m beginning to think however, not least with summer’s ‘bounteous harvest’ approaching, that it’s likely I’ll find so many night- flying insects I’m going to need to relax this rule if I’m to stand any chance of cataloguing my garden life in a realistic time frame.
Why is it that some - although interestingly, by no means all- species of moth are attracted to artificial light? The late, great moth expert Professor Michael Majerus had a wonderfully concise answer in his book Moths (The New Naturalist Library):
“I do not know”!
A common hypothesis is that moths, some of which navigate by the distant moon and stars, are fooled into trying to navigate by the artificial light. Possibly this is the answer, but if true you might reasonably expect to see moths approaching lamps in a navigational fashion via orbital, in-spiralling flight paths. Watch a moth approach a light trap however, and I have to agree with Majerus, it’s not easy to convince yourself you’re witnessing 'navigation-in-action'. Moths often fly directly towards the light, flutter around it in seemingly haphazard ways, or seem content to settle some distance from it.
Hsaio has put forward (Jour. of Insect Physiology, Vol. 19:1971-76, 1973) an alternative theory that point light sources ‘interfere’ with the operation of moths’ compound eyes causing them to perceive regions of darkness (i.e. good places to hide) around a lamp where there are none. Again, Majerus isn’t convinced. Another of nature’s mysteries! Maybe a reader here has a comment?
To the moths themselves: Firstly, attracted to my light about a week ago, the moth in photo 1. I struggled to identify this one at first, but then caught sight of a photo of The Yellow Horned (Achyla flavicornis), in a slim photo-guide (G.Hyde, British Moths, Jarrold Colour Publications) I’ve had since I was a boy. The larvae (you can find a photo on Ian Kimber's excellent UK Moths site) feed on Silver and Downy Birch from mid-May to July before pupating to over-winter and emerge as the adults found from late-February to mid-April. I read that the Yellow Horned is a member of the Thyatiridae family of moths represented by only nine species in the U.K.
On the same evening, photo 2, a March Moth (Alsophila aescularia), the green larvae of which (again, photo's available on Ian Kimber's site) feed on many broad leaf trees including Oak, Willow and Birch. The adults fly from late February to April and over-winter as a pupae. The March Moth is notable for being one of a small number of moth species where the female is flightless. You can find a photo of a wingless female here.
Why it is that a small number of moths can ‘get away’ with having no wings, whilst all the rest expend precious energy growing them is...yep you guessed it...another of mother nature’s mysteries...at least, it is to me. Comments anyone?
Monday, March 16, 2009
In my last posting on the Song Thrush I introduced my home-made camera 'trap' and mentioned that this gadget was one of a number I've been cobbling together:
Ladies and Gentlemen, a round of applause please for... (photo 1) ...the Skinner/Walloon Moth Trap!
One of a number of moth trap designs you'll find on the web, the principle of the Skinner trap is simple enough: A lamp to lure the critters towards a box fitted with a 'lid' comprising two sloping sheets of plastic that don't meet in the middle (leaving a gap of about ~1inch) . The moths flutter around the lamp, land on one of the slopes and slide into the box below, whence they aren't smart enough to find their way out. A few egg-boxes give them somewhere to hide.
To best attract moths you need a lamp that peaks towards the blue/ultra-violet. Best is a mercury vapour- or so-called actinic-bulb (you need the correct electronics (a 'ballast') to power either incidentally). I bought the various bits I needed from the Entomological Wildlife Group.
And the result?
Twenty minutes spent flicking through my copy of Moths (Waring and Townsend, British Wildlife publishing) and I'm confident I've met an Oak Beauty (Biston strateria).
The Oak Beauty is a member of the Geometridae family of moths of which there are some 20,000 known species with 300 occurring in the British Isles. Geometridae is from the same stem as geometer and is a reference to the measuring, 'inch-worm' gait of these moths in the larval stage. The caterpillars of the Oak Beauty feed on Oak, Hazel, Alder, Aspen, Elm and Sallow. They are well camouflaged to resemble twigs. I've never myself seen one, but you can find a photo of one here.
The moth I caught was a male, as indicated by his impressively large, feathery antennae (close up in photo 2). I personally find such structures a miracle of natural engineering.
Turning to my copy of the superb Moths by (the recently deceased) Michael Majerus (The New Naturalist Library), one thing I learn about the Oak Beauty is that it has a melanic form that occurs in Holland but not in Britain.
For those unfamiliar with melanism: Much as people can differ in their eye colour and yet all remain members of the same species (human'), so some moth species can show considerable variation in their wing pattern. Within one species, some individuals might have patterned wings whilst others might have, say, matt black wings. Careful studies over decades have shown that the places where moths with certain wing patterns predominate are those places where having e.g. black wings is a recipe for good camouflage from predators (say, birds).
The increased prevalence of black winged moths of the Oak Beauty's sister species, the Peppered Moth (Biston betularia), in heavily polluted areas is an extremely famous example of supposed evolution in action (a.k.a. 'survival of the fittest') and consequently has drawn a very great deal of study and heated debate. From everything and anything convincing I've ever read however, the basic conclusion I've drawn is: it's a fact! You'll find no better, more balanced account than Michael Majerus' book above.
Finally, I can't help but end with a comment on the truly wonderful 'folk law' names of moths. The Oak Beauty, The Burnished Brass, The Twin Spot Quaker, Mother Shipton...- the list goes on an on. I commend the following link to one of my all time favourite poems: All These I have Learnt, by Robert Byron.