The beetle is dead, long live the beetle

The decline of the leaf beetle (Chrysomelidae) Chrysomela tremula is well known (e.g. Cox, 2007; Hubble, 2012), even though the causes of its probable extinction in the UK are not understood - possibly the decline of coppicing and/or a side-effect of insecticidal spraying. The last known record was from Warwickshire in 1958, so when its rediscovery was reported relatively recently from purple willow Salix purpurea in Cambridgeshire (Mendel & Hatton, 2012), there was much rejoicing. Then, shortly afterwards, the authors realised that this had been a misidentification and they had actually found C. saliceti, a species never before found in Britain (Mendel & Hatton, 2013). So, C. tremula remains probably extinct but we do have a new species. This doesn't mean C. saliceti is non-native - it is very similar to C. tremula and may simply have been overlooked - after all, their separation was tricky enough to briefly trick some very experienced entomologists until another one noticed and the error was rectified - which is how science works...

Then after a discussion at the recent Coleopterists' Day in Oxford, Howard Mendel was kind enough to post me a couple of specimens of the new species as I had never seen one.

Chrysomela saliceti approx 9.5mm long.

Chrysomela saliceti under different lighting to more clearly show the punctures on the pronotum and elytra.

The trick is to separate the two species - especially in case C. tremula is still hiding somewhere (or re-appears from the Continent). A paper about this is planned, but until then, there are two key features:

• The claw-bearing tarsal segment (two apical teeth on the underside in tremula, absent in saliceti).
• Dissection of males to check the tip of the aedeagus (equivalent of a penis).

Tarsus ('foot') of C. saliceti - the claws are visible but no teeth on the underside.

The aedeagi of the two species for comparison.

References

Cox, M.L. (2007). Atlas of the Seed and Leaf Beetles of Britain and Ireland. Pisces, Newbury.
Hubble, D. (2012). Keys to the Adults of Seed and Leaf Beetles of Britain and Ireland. FSC, Telford.
Mendel, H. & Hatton, J. (2012). Chrysomela tremula Fabricius (Chrysomelidae) rediscovered in Britain. The Coleopterist 21(3): 132-135.
Mendel, H. & Hatton, J. (2013). Correction: Chrysomela saliceti Suffrian (new to Britain) not Chrysomela tremula Fabricius (Chrysomelidae) in the cambridgeshire fens. The Coleopterist 22(1): 19.
Warchałowski, A. (2003). The Leaf-beetles (Chrysomelidae) of Europe and the Mediterranean Area. Natura Optima Dux Foundation, Warsaw.

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!

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.

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...

What's in the box? Two of one, one of another (part 1)

While at the annual Coleopterists' Day at the Oxford Uni Museum of Natural History last weekend, I was handed a small wooden box with three pinned beetles in it. If you are an entomologist, this will be familiar as specimen-swapping is an important way of seeing varied specimens and passing on tricky beasties to specialists for identification. Not that getting a box of beetles was the real reason I was there - there's a really good entomology library to rummage through plus I gave this talk to my fellow beetle-nerds, now published in a slightly more formal version as Hubble (2013).

Box of beetles - two Aphthona on the left, and a larger Oulema.

So, to the beetles - they'd all been tentatively identified, but were passed to me for confirmation. I started with the larger one, 'a female, probably Oulema melanopus'.

Pinned female Oulema - note the blue-black head and elytra and red pronotum.

The female genitalia had been dissected and preserved in a drop of clear mountant. The important part is the little knot bottom-right where 'sd' = spermathecal duct.

An extract from Cox (1995) comparing the female genitalia of O. melanopus and O. rufocyanea, two very closely related species.

Looking at the images in Cox (1995), and the equivalent in Hubble (2012), it is clear that Figure 6 is close to the specimen here, including the short spermathecal duct and arrangement of other tubules. So, this is O. melanopus - good practice at a sometimes-tricky species group aided by some excellent dissection (not mine!). This may be even more useful given that unpublished and ongoing Swiss work on specimens of O. melanopus has shown that a small number of them turn out to actually be O. duftschmidi. There's no indication that this latter species exists in the UK, but it has a Western Palaearctic distribution so it's not impossible and I'll be keeping an eye out...


References

Cox, M.L. (1995). Identification of the Oulema 'melanopus' species group (Chrysomelidae). The Coleopterist 4(2): 33-36.
Hubble, D. (2012). Keys to the adults of seed and leaf beetles of Britain and Ireland. FSC, Telford.
Hubble, D. (2013). Progress report on the Chrysomelidae recording scheme. The Coleopterist 22(3): 103-109.

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.