Tag Archives: fly

Anthrax alert in Pennsylvania

Just in case you’re a fan of obscure diptera, I wanted to share some images of an insect I’d never seen before: Anthrax georgicus.

Colin Purrington Photography: Insects &emdash; Anthrax georgicus

I initially identified it as Ogcodocera analis, which looks exactly alike to the untrained eye (like mine) but isn’t found in Pennsylvania. Anthrax georgicus parasitizes tiger beetles, apparently. The females lay eggs near the entrances to tiger beetle burrows and then the larvae attach to the beetle larvae and suck hemolymph. If you live near a place with dense population of tiger beetles, keep your eyes peeled for this fly. Or read about them here, in a fantastic post by Matt Pelikan. I gather they lay eggs by dive bombing.

The next photograph shows what it did in response to my flash.

Colin Purrington Photography: Insects &emdash; Anthrax georgicus with wings spread

I searched around to see if all flies do this, but couldn’t find anything about light-induced wing spreading. I did find an article by Andrei Sourakov on the startle response of a long-legged fly, again caused by a flash — they exhibit a tumbling escape behavior (see paper for pics). In a separate paper, Sourakov discusses the startle response of skippers (Hesperiidae) — again, I highly recommend taking a look at the figures so you can see the insects during their escape tumbles. In hindsight, I should have played around with flash sync speed to see if I could measure how quickly it could spread its wings. The shutter speed I was using was 1/200 second.

Just in case I’m completely wrong about the ID (which I based on this page) and you’re an expert with a moment to spare, I put a better view of a wing at the bottom. The posterior margin of the alula looks convex. I don’t have a better view of the antennae, unfortunately, which I know would be helpful for Bombyllidae. As a side note, insects that are jet black but have shiny white parts are a complete pain to photograph.

Anthrax georgicus wing close-up

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Golden-backed snipe fly

This golden-backed snipe fly (Chrysopilus thoracicus) landed in one of my bird baths and drifted around for a few minutes on the surface tension. I’m not positive, but I think I’ve seen them do this in past years, too. I wonder whether they are looking for mosquito larvae, or perhaps adults. These flies have predaceous mouthparts, so they clearly hunt something. Sure wish somebody would PCR the gut contents of these things and let me know. Anyone ever seen them take something down?

Colin Purrington Photography: Insects &emdash; Golden-backed snipe fly (Chrysopilus thoracicus)

Here’s another one, albeit one with a damaged eye:

Colin Purrington Photography: Insects &emdash; Golden-backed snipe fly (Chrysopilus thoracicus) with dented eye

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Copulating robber flies, with snack

Mating robber flies (Promachus princeps, I think) on rabbitbush. Female is holding some type of cerambycid (perhaps Crossidius hirtipes), which she probably caught prior to the male approaching. I don’t think it was a nuptial gift from male (though that was my first thought). Female robber flies have been observed eating males, which are smaller, so waiting for a female with a meal is a good strategy for males who want to love and then live some more. Female robber flies with meals in hand are also less likely to resist mating attempts. Madras, Oregon.

Colin Purrington Photography: Insects &emdash; copulating-robber-flies

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