Learning Another (Fly) Stitch in the Tapestry of Patchwork Prairie

After all the hoopla of the holidays, I'm finally getting back to my projects, particularly the one where I'm learning to identify the different insects that I've photographed in the yard over the last 7 years.

With that goal in mind, I've started posting some of the insects that I can't identify on bugguide.net.  This wonderful site has generous volunteers that identify the insects they can in photos shared by people from all around the country.

The last time I posted any photos on bugguide.net was almost 2 months ago, so I was rather surprised recently to get a message in my e-mail box saying that someone had added comments to one of my submissions.  Checking it out, I learned that one of the flies I had posted from early November had been identified as a particular species of tachinid fly, Archyatus marmoratus.  Which meant exactly what?

I had been pretty sure that the fly, which I observed feeding on aromatic aster blooms, was a tachinid.  And it was.  Tachinids are rather large flies that look like very hairy, even bristly, house flies.  Despite their homely appearance, they are considered a beneficial insect.  In their larval stage, they are parasitoids, because their larvae grow inside a variety of other insects and kill those insects as they grow.  Often the species parasitized is specific to the species of tachinid fly, so finding out the species of tachinid fly gave me a good chance of learning how this particular insect fit within the community of plants and animals in our yard.

Googling was in order...and rapidly accomplished.

I didn't find a lot on Archyatus marmoratus during my quick Google search, but what I did find was reassuring, even exciting.  This tachinid species is not completely host specific, but it does parasitize caterpillars in a specific group of moths, Noctuids, particularly within a group of caterpillars that includes armyworms, budworms and other pest species.  The female fly lays her eggs in the area where host caterpillars are likely to occur and, after the eggs hatch, the young fly larvae hitch onto appropriate host caterpillars when they come by.  Each caterpillar that picks up a tiny fly larva eventually gives up its life, producing one adult tachinid fly in the process.

So, for every adult fly I see, an armyworm or budworm gave its life.  For every adult A. marmoratus fly I see, an armyworm or budworm didn't make it to adulthood to reproduce.  For every adult A. marmoratus I see, a new generation of tachinid flies has a good chance of appearing to help keep next year's armyworm and budworm populations under control.  And along the way, my asters get some extra help in pollination.

All in all, it's a mighty sweet deal, despite being all wrapped up in a pretty homely package.