Unexpected egg-flies

Back in January, my wife showed me a blackbird egg she'd found in the garden. It looked whole, but was incredibly fragile and broke almost as soon as I picked it up, clearly already being cracked. I expected maybe a whiff of something nasty, but there was more going on than I expected...

Inside the egg... lots of invertebrate action.

Naturally, instead of saying 'yuk' and throwing it away, I had a closer look. The orange inveretebrates are mostly fly pupae plus a few larvae. The black shapes are pupal skins of something already emerged, and the large larva in the middle something else entirely. A quick look in Smith (1989) jogged my memory that the smaller ones were probably juveniles of the Psychodidae, also known as moth-flies or owl-midges. The larvae of many species are associated with decaying organic matter, so the inside of a failed egg is a plausible hiding/feeding place whether the goo insode is egg material or something else that had seeped in. Beyond that I couldn't tell, so I put them in a hatchery and waited. After not too many days this is what I found...

Pupae, pupal cases and adults of a psychodid fly.

In total there were 15 pupae and these soon started to emerge as adults. The small size, their shape, and their hairy/feathery wings mean they don't look like typical flies, but that is exactly what they are - as you can see below, they have a single pair of wings, the other pair reduced to drumstick-shaped balance-organs (halteres). Psychodidae are not an easy group to work on (especially if you are not that familiar with them), and identifiying the flies to genus, let alone species, would require time, a microscope, and a copy of Withers (1989). I won't go through all the steps, but here are a few key features:

There are two veins (dashed lines) between the two main forks in the wing veins (circled).

The arrow indicates the eye-bar - an extension of the eye above the antenna. The circle indicates the pale haltere mentioned earlier - yes, these realy are flies!

 The antennae are an important feature too, but take care when keying out genera and species...

The key asks whether the antennal segments are barrel-shaped or have an elongated stalk. These look barrel-shaped but...

...if you remove a segment you can see that the barrel-shape in this case is formed of hairs that hide the real shape - the dark segment clearly has a stalk.

So, after quite a bit of deliberation, this keyed out as the genus Psychoda. I'm less certain about the species (not only can they be difficult to separate, but the taxonomy of Psychoda needs to be revised), but it might be P. alternata (the stripy larva in the first photo matches this, as does the foul habitat). Withers (1989) doesn't list Hampshire for this species, but the Psychodidae are under-recorded, and he does mentioned Wiltshire and Sussex, so it wouldn't be a surprise. That's enough for now - I shall leave you with some more juveniles, feeding/hiding merrily in the goo...

Psychoda - three pupae (complete with a pair of pupal horns for breathing) and a larva.

References

Smith, K.G.V. (1989). An Introduction to the Immature Stages of British Flies. Handbooks for the Identification of British Insects 10(14): 1-280.
Withers, P. (1989). Moth Flies. Diptera: Psychodiae. Dipterists Digest 4: 1-83.

Little larvae that love leaves

As you may know, I specialise in leaf beetles (Chrysomelidae) and quite often get sent specimens to identify as I run the national recording scheme for this family. These are usually adults, but now and again juvenile stages which are more difficult, but also useful reference material, especially as I (eventually) intend to write a guide to their identification. Some months ago I was sent some larvae preserved in alcohol to see if I could confirm whether they were Chrysolina marginata. It took me a while to find the time for this (it's been a busy year), but here's the process.

Tube of preserved larvae.

Contents of the tube. The larvae are of different stages (instars) and the largest ones are around 7-8mm long. The anal proleg is visible (especially in the specimen top right) and this is a feature of Chrysolina.

Sensory structures on the head. There are no compound eyes, but in Chrysolina there are six ocelli (simple eyes) on each side of the head as indicated by green arrows, four in a rough square and two the other side of the antenna which is circled in blue. The segmentation of the small antenna is clearly visible, including the small segments/structures at its tip.

Side view of one of the larger larvae. The blue lines show the joints between segments. The green lines show sclerites (hardened patches) arranged in irregular rows.

The end of one of the legs, showing the tarsal claw. The inset shows that the outline (solid) has no protrusion at the base. This is a feature of C. marginata with some other species having a protrusion (dotted line).

Close-up of the body surface. Sclerites are shown in green circles. The pale blue arrows show intermediate secondary bristles with small dark patches at the base of each. Between these there are tiny dark dots of microsculpturation as shown within the dark blue outlines. This mixture of features is seen in C. marginata.

So, the combination of features, along with the keys in Marshall (1979) and Zaitsev & Medvedev (2009) confirms that these larvae are C. marginata - easier than larval identification often is, and provides information that is due to be used in a report later this year.

References

Marshall, J.E. (1979). The larvae of the British species of Chrysolina (Chrysomelidae). Systematic Entomology 4: 409-417.
Zaitsev, Y. M. & Medvedev, L.N. (2009). Larvae of Leaf-beetles of Russia. KMK Scientific Press, Moscow. [In Russian]

March of the green vomit-grubs

As you may know, I am a stakeholder in a nearby community farm, here in the sometimes-sunny south of England. We grow many different crops and one of these is a small patch of asparagus. So, I was interested to see some beetle larvae eating the leaves and stems. Fortunately they don't seem to be affecting the asparagus growth noticeably so they've been left where they are (we don't use pesticides but could remove them by hand if they become a problem). Handily, I specialise in chrysomelids (leaf beetles) and recognised them as larvae from this family: the small shiny head capsule, and the body widening towards the rear then coming to a blunt point is typical. I've been looking at writing a guide to juvenile chrysomelids so in this case, knew they were larvae of the asparagus beetle Crioceris asparagi, and the presence of the distinctively colourful adults confirmed it.

Larvae of Crioceris asparagi along an asparagus stem. Adults in the background.

Late instar larva of C. asparagi eating an asparagus stem. This mature larva is close to pupating and shows a typical chrysomelid larval shape (though some differ greatly especially the tortoise beetles in the subfamily Cassidinae).

Larvae such as this are clearly potential prey for insectivorous predators that like juicy grubs. However, while some chrysomelid larvae hide and protect themselves with shields of their own faeces and shed skins, this species has a different approach. When threatened, it arches backwards, raises its head and regurgitates a droplet of partly digested food onto its attacker. This might not do much to a human but could be noxious to a smaller organism, causing the larva to be avoided or giving it time to drop off the plant to safety.

C. asparagi larva with a regugitated droplet on its head.

C. asparagi larva having used its droplet against my threatening finger.

In contrast, a chrysomelid larva (unidentified) with a shield of faeces and shed skins.

Assuming the larvae survive to pupate and emerge from their soil cocoons as adults, their defence changes greatly as they are colourful, warning potential predators that they are (or in the case of this species, are pretending to be) toxic - something known as 'aposematic mimicry'.

C. asparagi adult.

C. asparagi adults creating the next generation.

So, for now I'll enjoy these interesting beetles - hopefully they won't become too numerous...

Nest of tiny delights

Wow - a month since my last post - there has been no shortage of wildlife to write about, just no 'spare' time to do the writing. However, the paid stuff is quiet for a few days at least, so I thought I'd share some observations of the small and hidden, to be precise what I found lurking within a used-and-the-young-fledged robin's nest.

The robin's nest before dismantling.

You never know what'll be hiding in a nest (whether bird or mammal) - there's always the possibility of some under-recorded parasites, plus the array of small invertebrates that simply use the structure as their own. So, a white tray, various tweezers and pins and some time later, this is what I found, along with quite a few Collembola (springtails) and Psocoptera (barklice) which I didn't collect on this occasion as I knew I would have time to work through the identification.

One of three similar pupae a few mm long, currently in my hatchery.

Another pupa, also a few mm long.

A very young spiderling, highly active and I think one of the wolf spiders (Lycosidae)

A tiny dead wasp, probably one of the Pteromalidae, possibly predated by a spider.

The exuvia (skin) of, well, I'm not sure...

Alive and active, the larva of what is probably a 'carpet beetle' (Dermestidae).

So, not much in the way of definite identifications - with juvenile stages, that tends to be difficult, though if any are successfully raised to adulthood, I will as ever update the post. Also, no parasites, but there was good evidence of a thriving community of small invertebrates potentially living out their whole life cycle in the structure of the nest with larvae, pupae, evidence of emergence, predators and prey.

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.

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!

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.

The Great Juvenile Chrysomelidae Project

You know I like invertebrates, especially insects, in particular beetles, and that I have an inordinate fondness for the Chrysomelidae (leaf beetles). You may even know that I published an identification key to the adults of British species. However, I have (foolishly?) decided that this isn't enough and am therefore embarking on a project to (eventually) produce some sort of identification guide to juvenile chrysomelids - eggs, larvae and pupae.

Why? Well, for many of the species, the ecology and life histories are poorly understood, and many juvenile stages are undescribed. So, it's first of all, an opportunity to summarise where more research/beetle-hunting is required. If the larva of species X has never been described, then there's an opportunity to try to find it. This allows the biology of the group to be better understood and in turn, conservation measures to be more appropriately designed and applied. The better we know them, the better we can protect them.

This is why the first step is the creation of a spreadsheet covering what is known/published for each species on the British list so that I can see where the genuine gaps in our knowledge lie. I have a draft of this spreadsheet and what I'm after is feedback to see what I've missed - presumably some stages/species are covered in publications, grey literature, theses etc that I've not managed to find, as well as observations that have not been written up in keys or formal descriptions. Some blanks could be filled in with a fair level of confidence e.g. more 'earthen cells' for pupal location, but I've erred on the side of caution and left blanks where there's no published (or directly observed) confirmation I know of. There's also a list of all the references I've found so far.

Interested? want to help?

If you'd like to check the spreadsheet and see if there's anything you could add to it, please get in touch so I can email it to you (if there was a wiki function here, I'd use that, but there isn't...). Then simply send any additions to me citing the cell number in the spreadsheet where it should go (either by email or a comment here).

I hope that all makes sense and look forward to seeing what I've missed - I suspect this is going to be a long project...

A chrysomelid larva, but which one?

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.