With the end of November, bugwatching will also slow down. By this time the whole island had at least one hard freeze that killed many invertebrates. And even without a frost, by the end of November many insects have simply taken their course, aging and dying, their roles as producer, predator and prey having ended.
But I’m a resourceful guy. Over the years I’ve figured out many tricks for finding bugs in late fall and winter. Some species routinely overwinter as adults; Individuals of other species can simply survive a little longer than their conspecifics. So if you know where to look, insects still exist.
An important place is the warm air pocket between our front door and the storm door. The west-facing front door warms up in the afternoon sun, and on all but the coldest or cloudiest days the result is a microclimate almost any insect would be happy with.
How they find this place and how they get in are questions I cannot fully answer. Perhaps the configuration of the panes in the storm door works as an ad hoc insect trap, with bugs having an instinctive urge to go up when they encounter an obstacle – work up the bottom pane and intrude through the gap where the panes meet overlap. Or perhaps crevices, from which warm air escapes, invite entry (it doesn’t take much distance for an insect to pass).
In any case, while the front door trick doesn’t work every day, it does produce beetles fairly regularly during the winter, and sometimes the species involved are interesting.
On Thanksgiving I kept an eye on the door and figured the weather was warm enough to evoke some insect activity. A few bluebottles turned up – these regularly hibernate as adults – and a few ladybugs looking for a mild spot to hibernate. But it was a tiny black and yellow insect that caught my attention.
Perhaps four millimeters long, this creature was powerfully built, with thick antennae and bulbous femora, or thighs, on its hind legs. I nudged it on a fingertip, hoping to get it in better light so I could photograph it, but just before I pulled the shutter, it took off.
I reacted with the self-respect of any naturalist, cursing profusely, and then began searching the living room for my prey. Amazingly, just a few minutes later, I found it parked in the same spot of sunlight I’d tried to move it into!
Once I had some photos to work with, the identification process went pretty smoothly. That’s not always the case, but odd-looking insects (and this one looked very odd) are usually easier to identify than generic-looking ones. In this case, the long, powerful antennae ruled out a fly of any kind, and the overall structure strongly suggested a wasp.
Many small wasps, especially those with oversized femora, fall into a wasp division called “Parasitica”. It is a collective term encompassing many evolutionary lineages that happen to share parasitic life histories. With Parasitica as my initial guess, I started scanning the 11 superfamilies in Parasitica on the website bugguide.net.
This site, a vast archive of identified arthropod photos organized by taxonomy, offers a handful of representative photos for each group. With Bugguide, you just narrow things down as much as you can with your existing knowledge, then scroll through the listings at that taxonomic level, look for groups with photos, and click on them that match what you’re trying to identify.
In this case, I quickly focused on the Chalcidoidea superfamily from “Parasitica” and then, after reviewing the options there, tried the Chalcididae family. Among the Chalkidids, the genus Brachymeria stood out as a very close match to my mysterious wasp.
Brachymeria is a large genus but poorly studied, with more than 300 species worldwide and about 30 species in North America. But only a minority of these species appear to be represented in photos online, and reliable information on how to identify these wasps is scarce. So genus is probably as far as I can get.
The members of Brachymeria belonging to Parasitica all have parasitic larvae. From eggs laid on or near a suitable host, Brachymeria larvae bore into their victims and eat them inside out. For most species in the genus, Bug Guide reports, the hosts are moths, with the wasps more likely to parasitize moth larvae or caterpillars than adults. Brachymeria is obviously good in the game: Bug Guide notes that some species are used as pest moth biocontrol agents.
This was my first experience with this interesting genus. I can’t find any previous records for the genus from Martha’s Vineyard, although it may be common here, just overlooked. In any case, it was a good “storm door find” and a welcome distraction at a boring point in the bugwatcher’s year.
