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Welcome to my blog

This is where I post various musings about wildlife and ecology, observations of interesting species (often invertebrates)
and bits of research that grab my attention. As well as blogging, I undertake professional ecological & wildlife surveys
covering invertebrates, plants, birds, reptiles, amphibians and some mammals, plus habitat assessment and management
advice
. I don't work on planning applications/for developers. The pages on the right will tell you more about my work,
main interests and key projects, and you can follow my academic work here.
Showing posts with label insects. Show all posts
Showing posts with label insects. Show all posts

Monday, 9 June 2014

Long-legged lovers from lakeside leaves

After holidays, after the backlog of work I returned to... it's time for flies - in particular the genus Dolichopus in the family Dolichopodidae (long-legged flies). As well as long legs, most male 'dolis' have very large genitalia, but a post title focusing on that feature might reach the wrong audience... Anyhow, I was watching what I think is D. popularis (there are several similar species in the genus) when I noticed courtship behaviour - so, out came the camera to document a romantic photo-story...

A single Dolichopus
Two males court one female (on the left)
One male is driven off, the other courts the female by standing on long legs over her and rapidly beating his wings.
He tried to mate but was rebuffed (he would dart behind her, but she moved away and turned round), so back to the courting.
This time his efforts were sufficient and the female permits mating.
Female post-mating.
Male post-mating - the large structure bent down from the rear of the abdomen is his genitalia.
Male post-mating.

Thursday, 8 May 2014

Orange agents of decay

While checking a bee-log in our garden, I noticed one of the holes had a dead fly in it. I removed it and was about the throw it away when I saw tiny orange dots on the surface. Because I am a nosy ecologist I put it under the microscope to see if there was anything interesting going on, and saw what looked like a microfungus growing out of the joints and bristle-bases of the fly.

Fly (possibly in the family Muscidae) with orange fungal growths.
There are some very interesting fungi that parasitise insects and I've written about one of them before. However, this looks different - maybe something simply using an already-dead fly as a substrate.

Fungal growths showing the thin threads of hyphae between the orange fruiting bodies.
Fungal fruiting bodies at the bases of the fly's bristles.
The fungal structure is clear - hyphae and fruiting bodies - but with most microfungi, it is necessary to look at the spores, so I made a slide and zoomed in.

Fungal spores x100
The spores are clearly visible as slightly curved spindles, each split into several sections by cross-walls (septae). However, though a mycologist would probably know this fungus by sight, I couldn't find anything that matched it, so sent my pictures to the British Mycological Society's facebook group. It didn't take long for one of the BMS to tell me that this was a species of Fusarium. This at least explained why I hadn't worked out what it was - most Fusarium species are soil fungi involved in decomposition of dead organic matter but I hadn't been looking at soil-dwelling species. If so, the fungus was simply decomposing the fly - which is what it does, and very usefully too; no soil decomposers = dead soil. However, some Fusarium are insect (and plant) pathogens, so it could have killed the fly before decomposing it.

Fusarium are varied, diverse (in terms of both species and strains) and not all well understood or taxonomically clear, though some cause plant diseases and others can infect humans, while one is the main ingredient in Quorn! So, the identification stops at genus on this occasion, but has introduced me to a fungus that, although I'd heard of it, and it may be growing all around us in the ground, I've never stopped to look at before. Thanks BMS!

Wednesday, 7 May 2014

Beetles love big butts and they cannot lie

Spring means many things - for many species overwintering adults re-emerge and set about the important business of reproduction. One common species that is often seen doing this is the green dock beetle Gastrophysa viridula. It feeds mainly on broad-leaved dock Rumex obtusifolius and related species and in April/May patches of dock can be seen with large numbers of these beetles. Such groups can be highly localised however - one patch of dock can have hundreds of beetles while a nearby patch on the same site seems to have none, possibly due to adults clustering for mate-finding purposes - it is not due to mobility as they can fly. Mating is a competitive activity though as males may try to dislodge rivals, and have foot-pads. These appear white around the sides of the tarsi (feet) to help them grip the female.

Two male G. viridula compete for one female.
Gastrophysa viridula as they are often found - a mating pair.
A dislodged male G. viridula draws its legs in for protection.
The females are particularly distinctive as they have swollen abdomens which extend beyong the elytra (wing cases). There are two or more generations per year (possibly up to six depending on temperature and other conditions) and the oval yellowish eggs can be seen in small clusters. The first new adults emerge in June and others appear through to September. They then overwinter from October to April.

Eggs of G. viridula.
Female G. viridula showing the swollen black abdomen.
The adults chew roundish holes in dock leaves, but the black larvae can skeletonise whole leaves until just a network of veins is left. For this reason, where certain Rumex species are considered invasive, G. viridula has been suggested as a potential biological control, though as ever introducing non-native species needs to be considered very carefully to avoid unwanted impacts on native species.

G. viridula larvae feeding on dock leaf.

Wednesday, 23 April 2014

Springtime beetles, legs go spring

Having a garden pond means occasionally finding dead things floating. No, not hedgehogs or other larger fauna - the sides are profiled so that mammals can get out - but sometimes incautious invertebrates drown. Naturally, if they look interesting (and haven't been eaten by pond skaters and other small predators), I fish them out for a closer look. When I saw a flea beetle (in the Chrysomelidae, my specialist group - they are in the tribe Alticini within the subfamily Galerucinae) I identified it easily enough as Longitarsus pellucidus, a common species, though it's always worth checking. It lives on bindweeds (Convolvulaceae) which are growing near the pond so presumably jumped into the water by accident when disturbed by a spider, bird, cat, human or other potential threat. However, it did give me an opportunity to look at why flea beetles are so named.

Longitarsus pellucidus - the swollen himd femora can be seen, as well as the elongate tarsus that gives it its generic name.
The hind femur in flea beetles is swollen to accomodate jumping muscles and the 'metafemoral spring' which is visible through the cuticle as a slightly paler comma-shaped structure taking up much of the inside of the femur.

Hind femur and metafemoral spring of L. pellucidus.
The spring is a long-oval chitinous structure coiled much like a loose fist. Muscles squeeze the spring closed and then a 'catch' is released and the stored energy is released, extending the leg so the beetle can jump.Here you can see a ligament extending from the spring to the tibia so the leg is folded when the spring is compressed. This mechanism differs from that in fleas which have a blob of resilin (a natural rubber) which is compressed instead of a spring. Although fleas may be more familiar for their leaping ability, some alticine beetles are actually able to jump comparatively further, and of course some of these beetles are no bigger than a large flea - smaller beetles jump further relative to their size (Schmitt 2004). Also, the spring may be useful for identification and for grouping species taxonomically by looking at similarities and differences in the form of their springs. However, this is not a mainstream technique, largely because of the difficulty of dissecting out the spring and the lack of readily available published material forming a guide to identification this way, although there is useful information in Furth (1988) along with images and drawings from various species.


References

Furth, D.G. (1988). The jumping apparatus of flea beetles (Alticinae): the metafemoral spring. In: Biology of Chrysomelidae, eds. P. Jolivet, E. Petitpierre & T.H. Hsiao, pp. 285-297. Kluwer, Dordrecht.
Schmitt, M. (2004). Jumping flea beetles: structure and performance (Insecta, Chrysomelidae, Alticinae). In: New developments in the Biology of Chrysomelidae, eds. P. Jolivet, J. Santiago-Blay & M. Schmitt, pp. 161-169. SPB, The Hague.

Thursday, 17 April 2014

What's in the box? Beetle-related joy (part 2)

Following on from identifying a couple of specimens of Aphthona pallida, I was left with one small dark beetle, another Aphthona. This was a female but also very well dissected, and keyed out quite easily as A. melancholica - a gloomy name for a dark-coloured insect.

Aphthona melancholica - female with genitalia dissected out.
As you can imagine, as the beetle is only about 2.5mm long, the genitalia you can see in the above photo are not large. They tend not to be as useful for identification as those of males (as the differences between species are so slight), but can be helpful and are included in some keys such as Doguet (1994). The structure visible here is the spermatheca - the structure that receives and stores sperm.

Spermatheca of A. melancholica
Reference

Doguet, S. (1994). Faune de France 80 – Coléoptères Chrysomelidae, Volume 2: Alticinae. Federation Francaise des Sociétes de Science Naturelles, Paris. [in French]

Friday, 11 April 2014

What's in the box? Beetle-related joy (part 1)

Sometimes I get sent emails with photos of beetles, sometimes I get little packets of unsorted beetles with a letter asking for identification, but sometimes I get beautifully, neatly mounted and pinned specimens and that makes my entomological heart happy. In this case some specimens of Aphthona flea-beetles (Chrysomelidae: Alticini) needing to be checked at species level.

Neat arrangement of Aphthona specimens
The two on the left are similar (yellowish with a dark stripe) and are what I'm looking at here (the other darker one will appear in a separate post). They are both possible A. pallida which needs checking as the species was only recognised as being British (Sinclair & Hutchins, 2009) a few years ago, so its abundance and distribution is not well understood. This doesn't mean it's only just arrived, but that it hadn't been noticed before and was probably confused with the similar A. nigriceps (Jobe & Marsh, 2012).

Probably Aphthona pallida - a male with the aedeagus dissected out. Beetle approx 2.5mm long, excluding appendages.
The yellow-brown colour with a darker head and partial dark stripe along the suture (where the wing-cases or 'elytra' meet) is typical. Looking more closely at the aedeagus, the end has a small blunt point which is the final feature needed to confirm that this, and the other specimen, are A. pallida - in this case found in Cumbria.

Aedeagus of A. pallida - note the small blunt point top left.

References

Jobe, J.B. & Marsh, R.J. (2012). The status of Aphthona pallida (Bach) (Chrysomelidae) in Yorkshire. The Coleopterist 21(1): 19-20.
Sinclair, M. & Hutchins, D. (2009). Aphthona pallida (Bach, 1856) (Chrysomelidae) is a British species. The Coleopterist 18(3): 155-157.

Monday, 17 March 2014

After the wet

It seems that our several months of almost incessant rain has finally come to an end, and spring is happening. Although I expect that some species will have suffered due to flooding (water vole burrows, soil-hibernating invertebrates...), some are starting to appear. So here's a quick non-technical introduction to a couple of garden-dwelling moths that have made themselves known to me recently.

A mature larva of the Old Lady moth Mormo maura. Note the bright orange spiracles along the side, and the black marks in the rear half. Approx 60mm long.
Head of larva of Mormo maura - note the shiny, speckled head capsule with ocelli (simple eyes) and small antennae
M. maura is a common species and I have previously seen adults in our garden, including one roosting in a shed. Ivy (Hedera helix) is one of its main food plants and we have plenty of that so it is not a surprise to see this species.

A couple of months ago, a series of storms destroyed many garden fences (not to mention causing widespread flooding) in the UK and while clearing up the debris, I found several pupae that had been dislodged. Most were put in our 'bug hotel' but a few were taken indoors to be hatched. One of these emerged a couple of days ago and proved to another common species, the Bright-line Brown-eye Lacanobia oleracea. It feeds on a wide range of woody and herbaceous plants and again is no surprise, but did provide some photo opportunities prior to release.

L. oleracea - the bright line is along the rear edge of the wings, the brown eye refers to the kidney-spots in this species.
Close-up of the wings showing the scale-patterns.
Side view showing the hairy and tufted thorax.
Portrait!

Wednesday, 19 February 2014

Jolly writing news

No close-ups of invertebrates today - just a quick post to say a big 'yay' 'cos I've just agreed with Pelagic Publishing that I'm writing a book on Leaf Beetles as part of their Naturalists Handbooks series. Woot! I've got a year to write it, then it's due out mid-to-late 2015... Let the typing commence!

Wednesday, 12 February 2014

Bum-bursting mummy-wasps

Yes, you know it from the title - it's parasite time. If I ever feel that tiny beetles are too easy to identify and I fancy a challenge, the parasitic Hymenoptera are the group of choice - huge numbers of species, tiny differences between them, and few accessible keys. Yay. To make sure I don't get lazy, I have a hatchery where pupae (for example those I dislodge cutting firewood, mending the garden fence etc) are kept to see what they turn out to be as adults, identified and maybe even released. Sometimes other things turn up, for example this mummified larva of the knot-grass moth Acronicta rumicis on a bramble stem.

Mummified larva of Acronicta rumicis
It's worth noting that this is not a pupa - it is the moth larva's empty skin stuck to the stem by the dark brown sticky substance you can see just behind the head. This 'glue' is released by the fully grown wasp larva by cutting a slit in the underside of its host. I have had the 'mummy' in a hatchery for several weeks, but this morning I found an exit hole at the rear of the dead moth larva, and a lively adult wasp scuttling and flying inside the container.

Acronicta rumicis 'mummy' showing the parasite's emergence hole
The parasitic wasp cooled down and quiet. 1 square = 5mm.
So, time for identification. It's a wasp of some sort within the superfamily Ichneumonoidea. However, the abdomen isn't on a thin stalk and the wing venation indicates it is of the family Braconidae rather than Ichneumonidae.

Braconid wasp showing wing venation
For comparison, the wing venation of the braconid Aleiodes praetor, from Huddleston & Gauld (1988)
Now, it's worth noting that there is no guide to British braconid genera or species. Shaw & Huddleston (1991) gives a key to the subfamilies, but beyond that, identification requires a variety of more-or-less obscure journal articles in most cases, and the taxonomy has undergone a lot of revision. Fortunately however, this is (for a braconid) a relatively straightforward specimen. Firstly, the subfamily key takes it to Rogadinae and secondly, the wing diagram above matches the specimen closely because (handily) they are the same - Aleiodes. In the most recent checklist (Broad et al. 2012) there are 37 species of this genus in Britain and all are believed to be solitary (unlike many braconids where many parasites develop in a single host, the best known probably being Cotesia glomerata AKA Apanteles glomeratus). Although species identification is challenging, there are some clues. For example, the first two abdominal segments (blue arrows in the photo below) have longitudinal ridges running along the middle of their upper surfaces and this is typical of the common species A. praetor.

Aleiodes sp. showing ridges on the first two abdominal segments (blue arrows)
I couldn't check this tentative ID myself - at least not without accumulating some articles I don't have ready access to and/or visiting a museum collection (even online there is very little in the way of images, keys and so on). So, I passed this onto some braconid specialists who have confirmed it isn't A. praetor (not orange enough, though there are more technical ID features required too!) and I hope I'll get a definite species ID soon. Until then, I await whatever else appears in the hatchery...

Ventral view of Aleiodes showing orange legs with some black areas, and orange mouthparts.
References

Broad, G. R., Shaw, M.R. & Godfray, H.C.J. (2012). Checklist of British and Irish Braconidae (Hymenoptera) [30th April 2012 version]. Free download here.
Huddleston, T. & Gauld, I. (1988). Parasitic wasps (Ichneumonoidea) in British light-traps. The Entomologist 107(2): 134-154.
Shaw, M.R. & Huddleston, T. (1991). Classification and Biology of braconid wasps (Hymenoptera: Braconidae). RES Handbooks for the Identification of British Insects 7(11): 1-126. Free download here.

Friday, 7 February 2014

What's in the box? Two of one, one of another (part 2)

Yesterday, the answer was Oulema melanopus - today I'm tackling the other two, much tinier beetles. They both look like the one below and were tentatively identified from dissection as male Aphthona euphorbiae. Why tentatively? Well, they can only be separated from closely related species (not to mention some taxonomic confusion with these which I might write about if it's ever resolved) by looking at the aedeagus - the male genitalia - and in these specimens they don't look quite like the standard images in books or on websites like this which are useful for comparison.

A specimen of Aphthona, possibly A. euphorbiae - it is around 2mm long, not including legs and antennae.
Looking at specimen #1, here's the aedeagus:

Aedeagus of A. euphorbiae.
This one's straightforward - it's fairly stubby and although it doesn't widen towards the end (the top), it has got the small, broad blunt tip on the otherwise more-or-less semicircular end. Definitely A. euphorbiae, so onto specimen #2:

Aedeagus of A. euphorbiae.
This one's similar, but under the microscope looked more elongate although the tip is correct. It's probably A. euphorbiae but with the possibility for confusion with A. atrovirens or A. ?atratula (the '?' indicates uncertainty about it's identity/taxonomy), it can be worth checking even common species as this can sometimes help unravel such difficulties, though in most cases it is simply the usual range of variation between individuals even in diagnostic features such as the aedeagus. Anyhow, time for a side view:

Aedeagus of A. euphorbiae.
The curved (but not too curved) form confirms it is A. euphorbiae - a common species but good practice in investigating features that can be tricky in specimens showing a little variation from the norm.

That's enough beetle-nerding from me. Back soon with... hmmm, haven't decided yet...

Tuesday, 4 February 2014

Mystery gall time

January was quiet on the blogging front - a combination of grotty weather and mucho other work. However, I'm back with a mystery gall sent to me by Phil Budd from the Southampton Natural History Society (although he found it in Enfield, Greater London). He found it (with about 50 others) in a sallow tree, Salix cinerea and had noted the presence of what looked like moth larvae living in/on it. Beyond this, identification remained elusive and so it was sent to me for further scrutiny.

Gall (approx 20mm diameter) on a Salix cinerea twig - it has clearly developed on one side of the twig and has a swollen and irregular surface.
One side of the gall was softer with fibrous material, possibly the remnants of a galled bud.

My first stop was the excellent Redfern & Shirley (2011), a standard (and affordable) work with excellent coverage of British galls, though the rapidity of change in cecidology (gall study) means here are always new species being added and new host-galler association being found. It quickly became clear that this is either a species not found in that book, or an unfamiliar form of a gall which is included. Either way, it was time to open the gall and look at the the larvae.

Larva (approx 12-14 mm long) from the Salix cinerea gall.
Opening the gall showed that there were several larvae inside and that they were still alive. I removed one which, from the arrangement of three pairs of true legs towards the front, a gap in the middle, then prolegs towards the rear, was indeed a moth larva. It has a darkened head capsule and first segment, bristles and a pinkish-brown colour, with paired dots on the segments in dorsal view.

Larva in dorsal view, noting the paired dots clearest on the front few segments.
This looks (to me) very much like the larva of Cydia servillana, a moth in the family Tortricidae which, although uncommon, is known to cause galls on this tree species. However, the gall is an elongate spindle-shaped swelling nothing like the knobbly and irregular gall seen here. It also contains a single larva, unlike the case here where there were several larvae together. So, what are the possibilities?

  • It could be C. servillana creating an unusual form of gall, or utilising an existing growth of the type sometimes caused by the tree's response to a wound of infection.
  • It could be a different species of moth which I can't find reference to or which hasn't been recorded before, at least not as a galler of S. cinerea.
  • An unknown gall causer such as that noted on catkins in Redfern & Shirley (2011).I have my money on this option...
  • Something I haven't thought of. Also distinctly possible!
Although I couldn't identify this for certain, there were some things I could do...

  • As the larvae are alive, try to raise them as adults and identify the moths that emerge.
  • Ask a gall-specialist - in this case I forwarded this post to the British Plant Gall Society.
As it happens the BPGS responded very quickly and confirmed one of my maybes/suspicions - it is probably the unknown call-causer, maybe a virus or phytoplasma (specialised bacteria that parasitise the phloem and are transmitted by sap-feeding insects much as malaria is transmitted by mosquitos) that distorts catkins, and the larvae are simply using the structure for shelter. So, the gall itself remains a mystery, but the moth may be identifiable if it develops to adulthood - if so, I'll post an update. Until then, you can see that the larva I removed is alive and well...

The gall is held above the larva which then climbs onto it and begins to investigate the various holes and crevices.
The larva continues to explore.
After a few minutes, the larva entered the gall - hopefully it will pupate and emerge as an adult.

Reference

Redfern, M. & Shirley, P. (2011). British Plant Galls (2nd ed.). FSC, Shrewsbury.

Tuesday, 10 December 2013

A tiny clue that looks like poo

Sometimes a seemingly innocuous observation can lead onto an interesting ecological story... A couple of days ago while collecting bramble and raspberry leaves for my stick-insects, I noticed a small black-and-white cocoon attached to the underside of one of the leaves.

Black-and-white cocoon, 6mm long
Although the occupant has clearly emerged as an adult, I wondered if the distinctive black-and-white cocoon might be identifiable, at least to family level or similar. A quick web search made it clear that this was the pupal cocoon of an ichneumon and it didn't take long to find out that the pattern (which maybe camouflage it as bird-dropping or piece of mould?) is characteristic of the genus Hyposoter (subfamily Camploplaginae).

At least 15 species of this genus can be found in the UK and they parasitise the caterpillars of various butterflies and moths such as the Lymantriidae (tussock-moths), Pieridae (butterflies - whites and yellows) and Lycaenidae (butterflies - coppers, hairstreaks and blues). They do so by the female wasp laying an egg in the host caterpillar, piercing it with her ovipositor. Once hatched, the wasp larva develops inside its host which shrinks, becoming a hard,  brittle shell - effectively mummified. When ready to pupate, the wasp larva spins a cocoon inside the larval skin (or in some cases the host skin splits and the wasp pupates outside) and this creates the black-and-white patchwork pattern - it takes about a month from the egg being laid to a new adult emerging.

I don't know which Hyposoter this is and I doubt that it's possible to tell from just a cocoon. However, one of the British species (H. ebeninus) has been filmed going through its life cycle, and this is certainly a candidate for the species here as the adults match ichneumons I have seen but not identified (though that isn't a reliable indiactor - they are a diverse and tricky group to ID), and parasitises the cabbage white butterfly (Pieris brassicae) which is common here. Again, this is not enough for an identification, but it is something I can look out for next season. In any case, I hope that's an interesting little ecological tale from a passing observation.

Close-up of the Hyposoter cocoon showing silk threads attached to the host's mummified skin.