Sometimes, life is just a blur

No, despite the title, I'm not talking about being far too busy to fit everything in (though that's often true), or having hazy recollections of evenings past due to the influence of rum... Instead, I want to give a little insight into the nature of some enquiries I receive from non-entomologists regarding the identification of invertebrates.

First of all I have to say that I like receiving such requests - I may not always have much time to devote to them, but I do try, and am always pleased that someone has put in the effort, and been interested enough, to photograph an invertebrate and then (often after having tried a general insect book and the web) bothered to find someone - me - to contact. Much better than squashing the unknown!

So, when my mother-in-law got in touch a few days ago saying that a guy (Scott, if you're reading this) doing hedge-trimming had found (and I paraphrase here) 'a big insect like a dragonfly with a stinger' on his leg, it was good to know that it had been put on a leaf and photographed. My initial thought was 'ichneumon' because dragonflies are pretty straightforward to recognise as a group (including the damselflies) and Britain doesn't have many other long, thin, large insects with anything resembling a 'stinger'. I wasn't sure how far I'd get with identification - with around 3,300 species in the UK alone, many of which are very similar, and no single guide to them, it isn't an easy task even with a specimen - from a photo, species-level ID is usually impossible. Still, I was curious and asked for the photos to be emailed to me, and this is one of the set I received...

The mystery ichneumon

Well, the first thing is it is certainly an ichneumon (a type of parasitic wasp, although they are sometimes called 'ichneumon-flies' despite definitely not being flies), and quite a large one going by the ivy leaf and Scott's thumb for scale. However, beyond that it is a little more difficult. It is black with orange legs, a common combination for ichneumons, and has a long ovipositor. This is the 'stinger' but in reality isn't a sting; although some ichneumons (such as the orange-yellow ophions that turn up in moth traps) do sometimes give human fingers a bit of a jab, they are essentially harmless to us. The structure is actually an egg-laying tube and is long because it is used to probe into wood where the host insect larva lives. An egg is laid in (or on, with the young ichneumon larva burrowing inside once hatched) the host and the rest is, well, parasitic - suffice to say the host does not survive having an ichneumon growing inside it. Hosts include beetles, moths, flies and so on, varying by ichneumon species. So, is there anything else I can tell from the photos?

Side view of the mystery ichneumon

You will have noticed that the photos are a bit blurry (hence the title) - cameraphones and compacts often seem to decide the background is more interesting than the real subject - and often this would mean I couldn't use them. However, in this case it makes little difference as ichneumon ID by photo is often uncertain at best in any case. Here I can see the overall size and colour - for example there are no white spots or bands on the abdomen, which means it isn't our largest ichneumon, the sabre wasp Rhyssa  persuasoria. The size rules out most species, and the long ovipositor means it isn't a species of Pimpla (see below). Instead it is likely to be either Lissonota or the more localised Ephilates. Being late in the year, it is possible this individual was avoiding cold conditions and is simply active later than expected - certainly it dropped to the ground and was lost in pant material rather than flying away.

Whichever it is, the specimen is certainly impressive. I find this group of insects intriguing and am slowly  learning to identify them - it's a long process - and the species-level names are often indicative of their parasitic reproductive strategy and habit of hunting openly and actively for hosts; instigator, punctator, divinator, fornicator, consortana, dissoluta, inquisitor, insertana and so on. If you are interested, Broad (2006) provides a useful test key to subfamilies here. Beyond that, it's a matter of accumulating useful webpages, books and articles, and finding hymenopterists to help you - Fitton et al. (1988) shouldn't be too hard to find and covers the subfamily Pimplinae, members of which are quite readily encountered, such as the one below which took shelter in our bedroom while we were on holiday last month...

A pimpline ichneumon, possibly genus Pimpla.

References

Broad, G. (2006). Identification key to the subfamilies of Ichneumonidae (Hymenoptera). Available online here.
Fitton, M.G., Shaw, M.R. & Gauld, I.D. (1988). Pimpline Ichneumon-flies. Hymenoptera, Ichneumonidae (Pimplinae). Handbooks for the Identification of British Insects 7(1): 1-110.