Lesson Time: Dobsonflies

So here’s the scene:

It’s 7:49AM. You’re in rural Virginia, walking down the stairs to meet your group of fifty seventh graders for breakfast (after being awoken exactly 7 times by one student during the night who insisted he was going to die). You get to the base of the stairs, open the door, and you see a group of students huddling around the water cooler.

Students never hover around the water cooler.

Using your six foot one, hundred and eight pound frame, you make your way to the front of t

he group and on the wall you see…


File:Dobsonfly Corydalus cornutus.JPG

Image Source

What do you do next?

Do you run?

Do you push the precious children out of the way, sacrificing yourself to the deadly jaws of the beast?

Maybe you just scream like a fourth grade girl, pass out, and pray that you don’t wake up as this monstrosity feasts upon your sweet delicious flesh?



Or Not.

Never fear, innocent civilians. It’s just a Dobsonfly!

Adorably Horrifying

So I saw This Post on the largest aquatic insect floating its way around the internet in the past few days and I figured I’d drop a post about it, since this is right up my educational alley. And I just like insects.

I love insects.

To me its the sign of a wonderful day when you stumble upon a Dobsonfly at 7:49AM after a long sleepless night. This is because personally, I find the Dobsonfly to absolutely adorable.

That’s right: Adorable.

What can I say, I like my women how I like my insects: rare, flighty, and borderline psychologically scarring.

File:Female Eastern Dobsonfly.jpg

Image Source

Honestly guys, how do you not want to take this fine foxy lady out to dinner?

But seriously. Let’s get into the facts.

Dobsonflies are one of the largest insects you’ve probably ever seen, and probably will ever see if you live in North America. The ones that live in the US generally get as big as four inches long with an occasional wingspan of six inches. They can of course be much much smaller, I’ve found a few that are nor more than two inches long and maybe three inches of wingspan. The mandibles (the big pincers) can occasionally be upwards of three quarters of an inch in length on the males, although they are much smaller in the females.

Fortunately, only the females pinch and they don’t hurt any more than a Deer Fly bite. The mandibles on the males are actually too large to get proper leverage in order to produce a strong grab. They are more often used in mating where they are just graspy enough to hold onto females, and in tricking predators into thinking those mandibles actually work.

Which makes sense right?

As I always tell kids: if you had the option of eating a hamburger with giant jaws on the front of it and a hamburger without giant jaws, you’d probably go for the one that wasn’t going to bite you first.

But at least the babies are cute and cuddly, right?

1313670.  A Dobsonfly larvae, Corydalus Neuroptera. Image Source


This is called a Hellgrammite. It’s the larvae of a Dobsonfly and, of course, this one does bite. That big black head there is practically a block of bitey-ness, with personal experience telling me they actually bite harder than adult females of the species. However this doesn’t stop anglers from catching Hellgrammites and using them as bait for just about anything that swims.

After the eggs are laid on the riverbank, usually on overhanging leaves, they will hatch and plunk into the water where they spend anywhere from one to three years as that adorable little guy above before pupating and ultimately becoming an adult… for seven days. Seven days of sex, sex, sex, sitting around on walls, sex, and then death.

I can’t say that sounds like a terrible plan.

Identification Clues

And finally there are a few look-a-likes to be aware of: Alderflies and Fishflies. Both of these are in the Order Megaloptera, meaning they look similar because they are rather closely related.

Here’s a quick “what the Hell is that?” guide to the differences:

(Alderfly SourceFishfly SourceDobsonfly Source)


  • Wings held at angles over body, almost tentlike
  • Small, generally under one inch
  • Non-feathery antennae
  • Mandibles are barely noticeable



  • Smaller than a Dobsonfly
  • Wings are held flat over body, but generally wings mostly overlap
  • Feather-like antennae
  • No noticeable mandibles


  • Body is Friggin’ Huge
  • Antennae are not feathery and are Friggin’ Huge
  • Wings are Friggin’ Huge
  • Mandibles (on females) are Friggin’ Huge
  • Mandibles (on males) are even more Friggin’ Huge
  • Most common response to sight of one: “What the Hell is that thing? It’s Friggin’ Huge!”

Final Notes

  1. While Hellgrammites are relatively common, the adult Dobsonflies can be very hard to find due to their short lifespan. Your best bet would be to set up a light trap (even just leaving your porch light on) in late spring to summer. This only works if you live relatively close to a stream, creek, or river however. If you’re not by a body of water, you’re probably never going to see one.
  2. Dobsonflies are chill. You can pick them up, show them around, and they will generally do nothing but make an angry posture with their mandibles and bodies. They can literally sit around and do nothing for hours. I can hold one in my palm for an hour talking to students, put it back on a wall, and return six hours later to it still sitting in the same spot.
  3. If you ever get the chance, watch a Dobsonfly fly. It’s absolutely hilarious to me for some reason. It just doesn’t seem like it should be able to fly.

2 thoughts on “Lesson Time: Dobsonflies

    • Yeah, I had only seen one adult in my whole life until this summer. And that first one was just a small female. But down here I’m living pretty close to the Shenandoah River and there’s at least one every day!

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