28. Tachinidae – à la carte

Last year was the “Year of the Moth” in which a few select participants competed to see how many moth (and butterfly) species they could find with the equivalent of one hand tied behind their back. The rules were that we couldn’t use light, so no moth traps, lamps in windows or hanging about under streetlamps. Instead we reverted to more old-fashioned ways of finding moths such as dusk patrols, torchlight inspection of nectar sources and treacle/sugar/beer/banana/ rum/wines mixture painted onto trees and fence posts, competing with the birds to find caterpillars, digging for pupae, scanning plants for eggs and leaf mines, and daytime expeditions to promising areas, net in hand. Points were awarded for each stage of each species, so if you found an egg, larva, pupa and adult of something you would get four points. It kept us occupied all year, and between the four of us we saw signs of 273 species.

At the thematic dinner before the prize ceremony we had stripey caterpillar entrées, farfalle pasta (at least it was supposed to be, but the supermarket ran out and we had to make to with conchiglie or shell pasta in honour of the geometrid shell moths), some resonantly named wines, appropriate music (Madame Butterfly) and bespoke gingerbread biscuits. The prize was a naff piece of Spanish pottery decorated with a vaguely butterfly shaped blob of glaze.

Tachina fera with beekeeper for scale

One of the disappointments of last year (apart from my not winning the prize) was that one of the caterpillars that I had found, fed and carefully tended with fresh leaves, pupated not as a moth but as a tachinid fly. These flies are parasites of many kinds of insects, or rather parasitoids, since most of them kill their host as they eat them up from within. Last autumn a patch of mint in the garden was home to half a dozen or so jovial Tachina fera adults enjoying the last of the sunshine – it’s hard to imagine being a caterpillar with one of those developing inside you.

This year’s tachnid looked at first glance like a slightly smarter than usual greenbottle, a goldbottle perhaps. But a few things mark it out as being different. Like Tachina fera it is very bristly, and under the tip of its thorax is what looks like a silk pillow – an enlarged subscutellum which is characteristic of the family. Starting from a gallery posted by the Tachinid recording scheme (byline – its a bristle thing …) and working backwards through some rather tricky old keys (the terse Royal Entomological Society key to Tachnidae by F.I. van Emden 1954 and the quirkily constructed British Tachinid Flies by C.D. Day, 1948) I arrived at the conclusion that this was Gymnochaeta viridis. Hosts for this species are given as Small dotted buff, Black arches, Pale tussock, Common rustic and Shaded broad bar, an eclectic set of moths. Fussy eaters evidently.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s