Friday, July 30, 2010

Giant Robber Fly


 Very few insects generate as much interest as these large predatory flies. They are called Giant Robber Flies, and being called a giant it a very apt term. They reach lengths up to 2 inches....which is incredibly large for a fly. They are sometimes called bee killers because of their preference for eating bees and wasps. I've seen these guys attack and eat bumble bees!!! It is a pretty impressive insect that can accomplish that feat.


 This large fly is feeding on a dragonfly. When I first saw this dragonfly I thought something had already fed on it, I reached out to touch it and that robber fly let it go and flew straight at me. Scared the CRAP outta me. I literally screamed.
These giant robber flies are in the family Asilidae. I'm not sure which species are pictured here, I know there are at least two different species, but for me they are difficult to ID to species. These giant robber flies belong in the family Promachus. These flies are found Worldwide, and seem to be ,more commonly seen during the summer months. They are often found in open grasslands, sometimes near timber lands. Look for them perching in sunny locations awaiting their insect prey, where they will fly out rapidly and grab with their powerful legs and carry back to their perch and feed.

Mating is an aggressive affair. Males will fly out and pounce on females much like they do when grabbing prey. They will remain interlocked tail-to-tail for some time. They are still capable of flight while mating. Last night I stumbled upon a pair mating and they flew quite rapidly into the woodlands near a pond and out of sight before I could capture an image of their behavior. These flies are very quick and difficult to approach.

9 comments:

  1. This has been a good year for big flies of all sorts.Had one come into my car while I was shooting and I thought I had a big bee.

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  2. I just started seeing these large robber flies in the past two weeks. They seem to be very plentiful this year.

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  3. Since you and I see the same bugs around the same time, I'm going to stay indoors for the weekend. Thanks for the heads up.

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  4. LOL, you are a crackup. If you seriously see any of these flies I'm going to consider it karma...or something

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  5. I've been seeing a lot of these down here in northern Alabama...and the other day...I saw one and I said...that is a BIG Robber Fly!!!
    thanks Shelly! A great read and I'm going to have to put the Kaufman book on my list. the Kaufman butterfly guide is great too!

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  6. Saw my first one a couple of days ago and thought it was some new hybrid creature! Took this long to figure out what it was. Are they aggressive towards humans or animals e.g. curious puppies or humans that get to close with their camera phones? PS Any info helpful -thanks. Allison in Houston TX

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  7. They are harmless to humans and pets as long as you don't grab one, then you might get bitten for your effort. The bite might itch for awhile and be painful at first, but otherwise nothing serious.
    I photograph them when I can, generally they are skittish and don't let people too close, so I love it when one sits still for the camera.

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  8. I had never seen a "Giant Robber Fly" before this evening. While pursuing my first sighting , attempting to capture it, I suddenly saw a number of them in a clearing on the north side of my house. The one I caught measured just a little short of 60mm.

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  9. I actually captured a pair mating! Let me know if you are interested in seeing the photo!

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