Monday, March 4, 2013

Trichoptera to Tachinidae

Well, it has been a while, hasn't it? I just recently got back into the swing of posting regularly. Before that there was a long silence, a diapause (as Bug Girl recently characterized her absence from blogging). And to be honest, the things I was posting about weren't terribly interesting. Minutia of The Code is a technical activity at best, a lawyerly pursuit at worst (reading the backlog for the ICZN-listserv shows this), and not something for general audiences.

I started this blog in 2008 during the first semester of my Master's degree, in part inspired from Bug Girl's Blog and the few other insect blogs around at the time. I wanted to improve my writing, and I wanted to relate my interest in caddisflies, a group I had just begun to investigate. Caddisflies will forever be my first love, no doubt, but in the denouement of my master's thesis I became interested in other groups. It was both temporary burn out and lack of funding in that direction; I was without a "real" job, working in a restaurant, trying to pay back some of my student loans. I had a brief, unpaid internship at Chicago Field Museum (which has had it's own recent financial difficulties), still operating under the assumption that if I just got enough practical experiences in museums one would actually hire me.

It was half way through that valley year that I discovered I was really missing research, and I was missing universities and academia. The long term revision of the North American Keroplatidae that I had been planning seemed like the perfect project for a PhD thesis. Unfortunately, the programs I applied to didn't agree with me, or more likely they didn't have the space or money for that sort of research.

Cutting to the point: I finally found a PhD assistantship! But the work was in neither caddisflies nor fungus gnats. This was an entirely new to me group of insects, an important and diverse group of flies called tachinids. 

A Plethora of Tachinids: Most look like the gray and silver ones at the right side of the third row.

Tachinid flies (Family Tachinidae) are a worldwide distributed, ultra-diverse family of true flies with around 8,000 described species, and many more yet to be described. And we think that all this diversity is relatively recent, with the stem group branching out around 30 to 40 million years ago. The really special thing about tachinids is that they are all endoparasitoids of other arthropods. By which I mean, they all do the 'Aliens' thing. Yeah, that thing. The young get into their hosts by some means, and there the larvae grow and slowly eat the host out from the inside. When they pupate, they burst out and metamorphose inside their last larval skin (called a puparium), leaving behind the empty husk of their host. Endoparasitoids (or the techinical term, koinobionts) do not make a good bedtime children's story (The Very Hungry Caterpillar this is not), but they are a great platform for studying evolution and evolutionary interactions. Parasitoids can be ultra specialist, like many tiny braconid wasps that have only one host species, or super generalist like the tachinid Compsilura concinnata, which feeds on over 120 species and across several insect orders. Most tachinids are in the middle range, with a few to 10s of host species. Why they aren't particularly host limited like other groups will be the subject of a future post.

The majority of tachinids attack plant feeding insects, especially moth caterpillars, sawfly larvae, and beetle larvae, and are probably a significant factor in controlling agricultural pests. A few species have even been mass released as active biological controls. And there are some tachinids which are pests in their own right, including the Uzifly which attacks silkworms and causes millions in damages to sericulture every year. Some of the more unique tachinid groups have unusual hosts, like crickets or stick insects, or ant queens, or stink bugs. There is even a tachinid that attacks trapdoor spiders (Antrodiaetidae).

It's a little funny to me that as important and ubiquitous as tachinids are, they don't really have a common name. The family name, Tachinidae, comes from the Greek word tachys meaning 'swift', so I guess we could call them swift flies. Other names people have used include: parasitic flies, hairy parasitoid flies, hedgehog flies, and bristle flies. None of those names have really stuck, despite being wonderfully descriptive, so people continue to use the abreviated form of the family name. In general, tachinids are small to large sized dark colored, hairy house fly like insects, often with patches of silvery wax, and sometimes with bright orange, yellow or metallic coloration. The hairyness is probably the thing that stands out the most about tachinids, and many of the individual bristles are used in identifying and classifying these flies. A good number of tachinid adults are flower feeders, and some are striking bee and wasp mimics.

If you want to learn more about tachinids, the best place to start is the Homepage for Tachinid Resources. There's also the Tachinid Times, an annual newsletter for tachinid research. This year's issue just came out yesterday, and it's a particularly nice one. Dr. O'Hara (the editor) was kind enough to allow me a full page to describe my intended PhD research, which I will be outlining more in detail next week. There are also lots of pretty pictures, so go check it out!