Usually, fear is the first emotion people feel when they see a dobsonfly. They are one of the larger flying insects in the Chesapeake region and have jaws that look like they came out of a horror movie. To add to their intimidating appearance, dobsonflies are nocturnal and clumsy in flight, so people usually encounter them at night. Does having a four-inch-long bug with one-inch-long jaws flying around at night not sound appealing? Fear not; they are far more interesting than frightening.

It turns out that only the males have incredibly long jaws, and the only ones they will attack are other male dobsonflies. They use their long jaws to compete with other males for territory. Female dobsonflies have shorter and more powerful jaws but only use them for self-defense, as adult dobsonflies do not eat.

Dobsonflies live for less than two weeks in their intimidating adult form but can live for years as larvae in local streams. The larvae are known as hellgrammites. Hellgrammites can grow up to be up to three inches long, and their appearance has been compared to a centipede. They have brown bodies with a large head, big mandibles and a segmented body. Each segment of their body has a set of legs and feathery gills. Hellgrammites hide under rocks and along the bottoms of streams. Unlike the adult dobsonfly, hellgrammites are ferocious predators that will eat almost anything that flows past their hiding spots, including small fish. The hellgrammite lives an eat-or-be-eaten life at the bottom of our streams, as it is also a favorite food of many fish.

So, the most important thing to remember about dobsonflies is that when they look their most intimidating, is when they are least threatening, and when they are in their larval stage, watch out for this fierce predator! At any stage, dobsonflies are a promising sight. Their reliance on clean, fast-flowing streams with rocky bottoms makes them a good indicator of stream health. The adults don't stray far from the water and rely on streamside vegetation to lay their eggs in the right place. They aren't as sensitive to pollution as other insects, like mayflies and stoneflies, but they can still be a good indicator of overall stream health.

They might give us the creepy crawlies, but the steep decline in insect populations is cause for concern, and conservation efforts that help them and other Chesapeake critters should be celebrated. Insects are often the base of the food chain and an essential indicator of the health of local ecosystems. Unless you're frequently wandering near streams at night, it's unlikely you'll encounter an adult dobsonfly. If you do, be thankful for the opportunity and know it is a sign of clean water near you. Enjoy the opportunity and keep your fingers safe from those mandibles.

Are you interested in protecting your local waterways? Visit our "Help Protect the Bay" page to learn about actions you can take in your everyday life.




Found a female on our deck this morning in Northwest NJ. 1st one I've seen...


Just seen one in my driveway. By the time I got my phone to take a picture,I couldn't find it. I'm in Ohio.


We just saw one of these at work in Southern Vermont, at first site it was pretty creepy, but after reading the article it was very interesting! I feel lucky to have seen one for myself.

Edward Jones

I saw one in White Bluff ,Tennessee last week. It was on the side of a home. I far as I know, it was no water nearby. I took a picture because I had never seen one. It was about 3 inches long.

Forest Hopkins

Just seen one today, a mile north of the ohio river. My son knew right away what was,he said it's is a dobsonfly.

Cole Story

I saw one inside a room of my house tonight I live in Manchester New Hampshire and I read that they live near clean water, so I guess we have a clean stream near our house thank you for this article I have never encountered one before and it scared the hell outta me ngl 😭🙏🏻 it was a female for sure by the description thank you again.

Ashley Naylor

My boyfriend and I just saw one tonight. It looks like maybe a male. We were wondering what it was. We live in Missouri. Thanks for the article its interesting. I also read they live as larval for 5 or more years, That is fascinating to me.


We live in Alabama and had never seen one. It was one our deck we don't have and steams or ponds on our property. Our neighbor does have a pond that just got filled back up. I knew the CDC was asking for moth samples from people in the south so we did catch it. Why are the migrating here?

Heath Dunn

Encountered one in my yard came here for info I live in north Mississippi and had never seen one before but I have 2 ponds on my property and a creek so I'm guessing my water is in rather healthy shape thanks for the info mine was a male

Earl Burns Jr

The adult female WILL certainly bite you. I am 70 and have hunted them to fish with all my life. And I have been bit many times by an adult female.

Nguyen Tien Anh Quach

I love the hellgrammites. It was and still is my mission to find them every time I get to sample macroinvertebrates.

I just wanted to say that although they do look like centipedes, they only have six legs. On each segment of the abdomen, there is a pair of gills, i.e., the wording is a bit confusing. The audience might think these guys have a gazillion of legs, while they only have 6!

But great article btw! I love aquatic insects and would love to see more of this, as we need to get the public to better appreciate these tiny creatures (perhaps not so tiny for hellgrammites!).


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