Wednesday, 26 January 2011


Image: Wikimedia
Male Eastern Dobsonfly
Oh. My. Gosh.

What on earth is this thing? It's huge! It has gigantic wings! It has massive... ANTLERS coming off its face! Has someone had a nightmare that's come to life or what?

What we have here is the Dobsonfly. An insect that can reach 12.5 cm (5 inches) in length, with a wingspan that can reach twice that. The most famous one is the Eastern Dobsonfly, specifically the male of the species, for it is he that has those huge, scary tusks.

Image: Wikipedia
Female Eastern Dobsonfly
I will add to the fear by saying that Dobsonflies have powerful jaws. OUCH! Except that males have such long jaws that they can't get the leverage necessary to inflict a strong bite. Some of the larger females on the other hand, can use their much more modest and manageable mandibles to cause pain and even draw blood. Sometimes the host who boasts the most would be better off keeping quiet. And sometimes it's the quiet ones you would do well to keep an eye on. (NINJA!)

Both males and females will raise their head and spread their jaws to deter predators. It probably works too. But it seems that males actually use those fearful tusks for the purposes of mating, like peacock feathers or deer antlers. It's weird how females are so often attracted to things that are completely useless. It is said that the male dobsonfly use their jaws not only for display, but also to fight with other males and also to hold the female during mating. So maybe they have some important function somehow. We'll have to ask the females.

Find more at memutic's channel. Wonderful stuff!

In truth, it may not be such a problem if they really were useless. Adult dobsonflies only live for about a week, it looks like they don't even need to eat. Instead, they spend most of their lives, several years, as freshwater larvae called hellgrammites. These have all the gills they need and strong (and short) pincers for eating the larvae of other insects. They are not great swimmers, spending most of their time under rocks. They also have small hooks at the tip of their tail for gripping, so that they don't get swept away in rivers and streams.
Image: Wikipedia
When the time is right, they crawl off to land, dig a hole in the ground to pupate in and an adult dobsonfly will emerge some weeks later.

Imagine going for a stroll in the woods at night and seeing one of these monsters clambering out of the ground fangs first! Maybe you shouldn't be strolling in the woods at night?


Brigitte said...

Very helpful. A bird just dropped a 3 inch male Dobsonfly in my yard and I had no idea what it was. Thanks for helping with the id.

Joseph Jameson-Gould said...

No problem, glad I could help!

92a69a7c-e7a2-11e2-ab26-000bcdca4d7a said...

I just saw one of these on my front porch while I was smoking a cigarette. Freaked me out a bit so I put a boot on top of it and looked it up on Google. It was pretty easy to identify by simply typing "Huge bug 4 wings large pincers". Found out what it was right away. It's still under the boot. I'm going to watch my mom move said boot tomorrow morning and watch her reaction. Might even film it.

Angela Mullins said...

Captured one tonight in my children's bug box. It was on my front porch. Freaky.

In west va

Paula Peterson said...

My 7 year old son just found a female one on our sidewalk. Ewww I can't get rid of these goose bumps.

Joseph Jameson-Gould said...

@92a69a7c-e7a2-11e2-ab26-000bcdca4d7a: Erk! That'll be a nasty surprise!

@Angela Mullins: Yeah, it's quite a picture. Not a pretty picture, but a picture.

@Paula Peterson: haha!

Lydia Boman said...

I live in Minnesota, have my whole life and have never seen one of these until today. It's almost the length of a dollar bill. Talk about a nightmare! Scared the crap out of my kids too. They thought it was a crab bug. Haha I want to know though, do they carry disease?? And how the hell did it get HERE?!!?

Joseph Jameson-Gould said...

I don't think they carry disease, but they do live in Minnesota!

Ones like this:

They're just a little secretive and aren't much attracted to anything humans have. Unlike wasps swarming your picnic!

Nicole said...

Never saw such a thing until tonight. My cousin and I have lived in rural PA our entire lives and lost our minds when this landed on our patio table at a bar. Everyone in the place came out to look at it. Truly looks like something plucked out of a nightmare.

Joseph Jameson-Gould said...

Ha! They definitely look quite nightmarish!

PLeach said...

The larva make excellent fishing bait. My husband used to catch them in the Raritan River in NJ. He'd break off the pincers with forceps before putting them on the hook. The smallmouth bass went crazy for them!

Joseph Jameson-Gould said...

Yeah, I hear fish love them. I wonder what they'd think if they saw what those tasty maggots become!

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