10 Dobsonfly Interesting Facts (And Their Larvae Too)

Did you know that DC comics launched a whole villain named after the larvae of dobsonflies? Read on to learn more such interesting facts about these insects.

The insect world never fails to amaze us with its diversity. If you are into nature and love to learn about insect species, the dobsonfly should pique your interest like no other moth.

The dobsonfly is one of the largest members of the insect world. It starts its life out as an aquatic bug and ends it flying in the skies.

It is most common in the Western Hemisphere, although you may also come across them in Central and North America.

Currently, there are30 species of dobsonflies around the world, but only one is common in the United States: the eastern dobsonfly (Corydalus cornutus)

Dobsonfly Interesting Facts

So, of all insects in the world, why would you want to learn more about dobsonflies? Let’s have a quick look at some dobsonfly facts:

They live their entire lives as larvae.

The life cycle of a dobsonfly is one of the most intriguing details about this species. The bug gets to spend only a tiny fraction of its life cycle as a mature adult.

The larval stage alone lasts three to four years, making the total lifespan of a dobsonfly quite impressive.

After this, the pupal stage lasts a few months, from winter to spring. Once the adults emerge, they live only up to a week at most – just enough to reproduce.

Hence, despite having a total lifespan of several years, these moths live only a few days as adults.

The adult stage is so short that at this point, they don’t even eat! They use their food stores from the pupae stage to find a mate and bring the next generation forward.

These bugs are hard to find: they only live near running water.

Dobsonflies are quite common, and you can find them all over the world. However, they’re especially abundant in Africa and Asian countries like Vietnam and China.

You can also find dobsonflies in Australia, Central America, and North America, although their subspecies aren’t as diverse in the western part of the world.

In the US, you will mostly find the eastern dobsonfly. In total, there are nine genera of dobsonflies, comprising dozens of species in total.

Their habitat is limited to places that are near rivers or running streams of water, where they live their lives as larvae, and then even as moths, they don’t go very far.

Some of them are large enough to cover your face.

Remember we mentioned that the dobsonfly is one of the world’s largest insects? You might be wondering exactly how big they are.

Well, these bugs can grow up to five inches long, and their wingspan may reach up to eight inches.

To give you a more visual example, a dobsonfly is large enough to cover most of your face. Don’t try to imagine it, or else you will have nightmares for the rest of the week!

However, not all species of dobsonflies are equally large. The five-inch-long ones are more predominant in Asian countries, especially China and Vietnam.

Some dobsonfly species are only two to three inches long. Moreover, the females are significantly shorter, not the least because they don’t have large mandibles in the front.

Regardless, this doesn’t rule out the fact that the dobsonfly has impressive dimensions.

They look like something out of a horror movie.

Dobsonflies share quite a resemblance with dragonflies, especially with their wings spread apart. Like dragonflies, they have four veined and translucent wings.

However, dobsonflies cannot fly as well as dragonflies.

The color of these soft-bodied insects varies between yellow and dark brown. The exoskeleton comprises three segments, and like most insects, dobsonflies have three pairs of legs.

The mandibles of a dobsonfly are easily noticeable due to their large size and sickle-like shape.

Although the adult forms vary from one subspecies to another, the basic shape and structure mostly remain the same.

Despite their appearance, they are mostly harmless.

The large size of a male dobsonfly, together with their sickle-shaped mandibles, can make them quite scary, but those mandibles are all bark and no bite. The real biters are the females.

The males cannot bite – the mandibles are mostly used to defend against mating rivals. Even if a male dobsonfly bites you, it would just feel like a strong poke because the mandibles don’t have enough leverage to do any serious harm.

However, we can’t say the same about female dobsonflies.

Although the female dobsonflies have smaller jaws, their mandibles are strong, and they have sharp pincers capable of dealing powerful bites.

If you handle one of them carelessly, you might even end up with a bleeding wound. However, you can breathe a sigh of relief since they won’t bite you deliberately agitate them.

Thankfully, neither the males nor the females are venomous, and the pain from the bite doesn’t last very long.

The larvae form of dobsonflies is called hellgrammite – and these critters are also strong biters. However, you would be hard-pressed to find one around since they live in the water.

They don’t like flying, but they aren’t bad at it either.

Despite having large wings similar to dragonflies, these bugs are nowhere as good as dragonflies when it comes to flying.

Although their exact flight speed is still unknown, they fly in a rather shaky and trembling manner.

However, they can still cover a significant distance when looking for a new water body.

Hellgrammite Interesting Facts

Now that you gathered some interesting knowledge about dobsonflies let’s learn about the larvae of dobsonflies – the hellgrammites.

The insect spends most of its time in the larval stage: this article would be incomplete if it didn’t cover hellgrammites as well.

They live their lives underwater.

Unlike adult dobsonflies, which move to land after pupation, hellgrammites are completely aquatic.

They prefer to live in shallow and fast-flowing parts of rivers, streams, and creaks, usually hiding under logs or rocks.

One of the most interesting things about hellgrammites is that they prefer to live in clean waters with well-balanced pH levels.

If you find these larval bugs in your backyard pond or dobsonflies near it, that means your pond is quite clean.

Even trace amounts of pollutants cause these insects to seek a different water body.

They eat a lot of aquatic pests and are great for keeping water bodies clean.

While dobsonflies don’t feed as adults, their larvae are aggressive predators in the water.

Hellgrammites hunt and feed on a variety of other aquatic insects, mayflies, immature chironomid midges, stoneflies, and even small fish.

Also, you should note that hellgrammites are fish food themselves. Anglers often use these larval insects as fish bait.

DC named a comic villain after them.

This insect looks a tad gross in their larval stage, somewhat resembling a centipede. They are so ugly; DC actually made a comic villain named after them!

They are generally black, tan, or dark brown, with flattened and elongated bodies.

In addition to the three pairs of legs, the abdomen also has eight pairs of leg-like appendages on the sides. Each of these appendages has a hairy or cottony gill tuft at the tip.

Each of the actual legs has a tiny pair of pincers beside the mandibles in front of the thorax.

Hellgrammites also have a pair of hooked leg-like appendages at their rear end that allows them to anchor to the surface and prevent themselves from getting washed away in the current.

They are usually two to four inches long.

They live their lives in the water, but that’s not where they lay eggs

Although hellgrammites are aquatic, adult dobsonflies don’t lay eggs in water.

Instead, they lay eggs in shady vegetated areas adjacent to water bodies or rocks poking out of the water’s surface.

Female dobsonflies can lay up to 3,000 eggs in the form of large egg masses. These egg masses resemble bird droppings which often get overlooked by predators.

The eggs take about two weeks to hatch. Once it’s time, the egg mass turns liquid. The hatchlings can now drop into the water and continue their lifecycle.

Wrap Up

We hope by now we have been able to pique your interest in dobsonflies! These insects look really scary, but they are actually gentle creatures who can’t do you much harm.

Thank you for reading, and keep on exploring the amazing world of insects!

Reader Emails

Considering their size and wingspan, it is no wonder that many of our readers have had an avid interest in these bugs.

Read a bit more about the interesting conversations that we have had with our readers regarding Dobsonflies over the years in the emails below.

Letter 1 – Dobsonfly

Any idea what this is?? Never seen this before in Townsend Massachusetts. Thx,
Erik

Hi Erik,
This is a male Dobsonfly.

Letter 2 – Dobsonfly

5 inches long with wings, and maybe pinchers??
We found this on the top of our garage. It’s about 5 inches long, kind of reminds me of a cicada(sp?) but is bigger than those I’ve seen … and looks like it has pinchers of some kind. I didn’t see one on your site and was wondering if you know what it is? I know you’re very busy but if it fits in your schedule, we’d love some help identifying it. Thank you,,
Hilary Evans

Hi Hilary,
We are very surprised that we haven’t gotten more requests this year for Dobsonflies. June and July are generally our peak months for sightings. Male Dobsonflies have those signature mandibles that make it virtually impossible to confuse this species to any other.

Letter 3 – Dobsonflies and Fishflies

Thanks for having this "little" guy on you page. I’ve seen Hellgramites before, but I never knew what they grew into. I spotted this one on the ash tray outside our office this morning. I thought you might like to add the picture to your collection.
Thanks!
Bob

Thanks for the great photo Bob.

Letter 4 – Dobsonflies and Fishflies

Hi!
I live in Austin, Texas and just found this nasty looking bug outside on my patio, clinging to the wall in the early morning below my porch light.
It has a large set of mean-looking pincers on the front of the head. The forward half of the body is dark, and the rear half is light tan and caterpillar-looking. I had to take the picture through the yogurt jar I captured him in. He is about 3.5 inches long.
I leave most outdoor bugs alone but was concerned that if I ran across him later accidentally, I might get a nasty bite. He aggressively threatened me as I repositioned the jar to get the photo.
If anybody wants him, come and get him!
Thanks!
Patty Pritchett

Dear Patty,
She is beautiful. He is an adult Dobson Fly, the larvae of which are known as Hellgrammites. The male has even moreformidable jaws which are used during the mating ritual in what humans might consider spousal abuse. They will not harm humans. We have additional information on our site.

Letter 5 – Dobsonflies welcome in Summer

Ed. NOte: Summer Sightings With summer here, we expect to be getting numerous identification requests for Dobsonflies. We thought this posting showing a beautiful male and female Dobsonfly from two different areas will help our readership identify this distinctive creature. Identify bug Location: Asheville NC June 21, 2011 8:11 am We saw this in Asheville NC on June 20. It was 3 – 4 inches long and on a fence post. Signature: SCBrit

Please Identify our bug Location: N. Ky. June 21, 2011 10:32 am This insect was found up inside of our umbrella. The body portion of the bug is almost as long as my pinky finger. This pic was taken in N. Kentucky, today, June 21, 2011. I have lived in Ky. my whole life and I cannot say that I have ever seen this before. Signature: Marlene Shoemaker and kids

dobsonfly_female_marlene — Female Dobsonfly

Dobsonflies are fascinating insects that display pronounced sexual dimorphism. The larger male also has significantly larger and differently shaped mandibles. Larval Dobsonflies are known as Hellgrammites.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Hellgrammite from California

Majave River Location: Mojave River, Southern Califorina July 4, 2011 3:40 pm We were at the Mojave River and saw this bug in the water. It kinda looks like a larva of some sort, but in all honesty i have no idea what it is and was hoping you would be able to identify it for us. Thanks for your time Signature: The Green Family

hellgrammite_mojave_green — Hellgrammite

Dear Green Family, This is the larva of a Dobsonfly, commonly called a Hellgrammite. Most of our specimens are of the Eastern Dobsonfly, though several species are known to range in California, however they are not well documented. This is one of the Western Dobsonflies. See BugGuide for additional information.

Letter 2 – Hellgrammite in the Snow!!!

snow insect Location: mt rainier national park, washington state February 25, 2012 2:20 am we saw this 6 legged, spiny insect on a snowshoe in mt. rainier national park (washington) late feb 2012. from limited, ignorant research– it looks similar to firefly and lacewing larvae but not exact. wished we would have put something down there to show size-but didn’t- was at least 2 inches long. thanks Signature: jen

hellgrammite_snow_jen — Hellgrammite in the Snow

Dear Jen, This sure looks to us like a Hellgrammite, the larva of the Dobsonfly. Interestingly, BugGuide has a photo, also from Washington, that was posted two years ago in February. That individual is also in the snow and there was speculation about why it was in the snow. Thank you so much- very nice to get an answer so quickly. we were right next to a spring fed beaver pond with numerous geothermal springs/vents. if that makes any difference with the strange location (snow) of a typical aquatic bug. Again- thanks again- Jen Hi Jen, Those details might be significant, but it is still interesting that there was another Hellgrammite sighting in Washington in the snow.

Letter 3 – Hellgrammite

crazy ant like centipede Location: tennessee mountains April 9, 2012 10:13 am this was found under a rock near a river bank, it tried to burrow into the dirt. It is spring and this was found near a cool mountain river. thanks for your time. it is about 4 nches long and maybe a half inch across the little things on its side do not move like legs..? this bug is about 4 inches long and a half inch wide. It was found under a rock on a pebble river bank in the tennessee mountains. it’s back ”legs” dont move and it was trying to burrow under a small plant. Signature: Heather Brannon

Hi Heather, You are not the first person who has mistaken a Hellgrammite for a Centipede. Hellgrammites are the larval form of Dobsonflies. Though they are not venomous and are not considered dangerous, both immature Hellgrammites and fully grown female Dobsonflies are capable of inflicting a painful bite if carelessly handled. Male Dobsonflies, despite their formidable looking mandibles, are not capable of biting humans. Hellgrammites are a prized bait among freshwater anglers.

Letter 4 – Hellgrammite

Subject: what is this bug? Location: Coventry,Ct May 23, 2012 6:47 am Mr.Bugman,what is this bug?My husband found it on a job site.It even attacked the tape messure when holding it up to it with his pinchers. Signature: thanks sheri

Hi Sheri, Try as we might, we have never been able to trace the origin or meaning of the name Hellgrammite, however it seems a very appropriate name for this Dobsonfly Larva. If you think the larva is a fierce looking creature, take a peek at this adult male. Dobsonflies and Hellgrammites are harmless, though it is possible to get a nip if the larva or adult female is carelessly handled. The mandibles of the male are showstoppers, however, one need not worry about getting bitten as they are not functional for biting. We have always suspected they are used for mating, however, we have never seen a photo to support that theory.

Letter 5 – Hellgrammite

Subject: What’s This? Location: Winter, Wisconsn May 29, 2012 8:38 pm This is a weird bug that my kids and I found in Northern Wisconsin at a cabin by the Radisson Flowage. During our 3 night stay over Memorial Day weekend 2012 we found 4 of these critters running around. Please help us know what it is. Thanks Signature: Clint Parker

Hi Clint, This is a Hellgrammite, the larva of a Dobsonfly, and they are generally found close to water. Hellgrammites are a favored bait for freshwater anglers. We will be scheduling your letter to post live to our site later in the week as we will be on holiday.

Letter 6 – Hellgrammite Pupa

Subject: Hellgrammite pupa Location: Black River, Springfield VT June 22, 2012 7:48 am Our daughter found this under a rock as she was fishing down at our local river. We love river-bugs (benthic macroinvertebrates), as I am the director of the Black River Action Team, a grassroots river group in Windsor County, in SE Vermont. We have this pupa in a terrarium; it’s been curled up and dormant (unless disturbed, then it wriggles around energetically!) since June 14th. So far, it’s been 8 days…I’m interested to learn how long the pupal stage lasts! I understand the females live as adults just long enough to mate and then lay eggs on structures or vegetation that overhang the water — like the bridge abutments where our daughter was fishing. Signature: Kelly Stettner, BlackRiverActionTeam.com

OLYMPUS DIGITAL CAMERA — Hellgrammite Pupa

Hi Kelly, We have just started getting Dobsonfly identification requests, and they generally continue until July, so we expect your Hellgrammite Pupa should metamorphose into an adult soon. Since warmer temperatures arrive later in Vermont than in the more southern portion of the range of the Dobsonfly, you might have a slightly longer wait. We are uncertain how long the pupal stage of the Dobsonfly lasts, but we know it is not more than a single season. We expect that pupation takes place in spring to account for a summer emergence. Daniel, this is great; thank you so much! I am learning more about bugs than ever before in my life, since moving to our home on the river bank in 2010. Lots of ID information comes from helping our state water quality lab do “bug picking” each January, but a lot comes from searching the internet and scouring your site. Learning how the macro setting on my digital camera works has been a big help — got some awesome close-up shots of a burrowing mayfly larvae a couple of years ago! Would you folks prefer more questions about identification, or are specific queries okay, like my question about the pupal stage of the hellgrammite? Cheers, Kelly Hi again Kelly, We would really like images of underrepresented species for our site. We don’t have as many aquatic insects as we would prefer. Please put the insect name in the subject line to grab our attention. That said, all inquiries are welcomed, but we can only answer and post a few a day.

Letter 7 – Hellgrammite

Subject: Ugly bug Location: North Goergia August 27, 2012 7:39 pm Hey my name is Kirby, and I found this thorny larvae, I’m guessing, while i was camping and never seen one before. They were every where, I didn’t kill it cause I didn’t know what it is, but I did relocate it far way from our tent. Signature: Kirby

Hi Kirby, We have never been able to trace the origin of the name Hellgrammite which is given to this larval Dobsonfly. The large numbers you witnessed might be one reason the Hellgrammite is a popular bait for freshwater fishermen.

Letter 8 – Hellgrammite

Subject: What’s this bug? Location: Grand River, northeastern Ohio December 2, 2012 10:14 am We found this bug in the shallows of the Grand River in NE Ohio in early november. Only the 1st 3 pairs of protrusions are legs, the rest are just spines. 4 inches long end-to-end. Never seen anything like it. What is it? Signature: Ian Griffith

Hi Ian, The aquatic Hellgrammite, the larva of the winged Dobsonfly, is a favored bait of freshwater fishermen.

Letter 9 – Hellgrammite

Subject: Caterpillar type bug found Location: Brazos River, Marlin, Tx March 30, 2013 7:23 pm We are in Texas and this is the second time I’ve seen one of these. It looks like a giant larvae or kind of like an earwig. It’s about 3 inches in length. I found it in shallow water under a rock on the Brazos River in Central Texas. Signature: Scott M.

Dear Scott, We love posting photos of Hellgrammites, the aquatic larvae of Dobsonflies. Hellgrammites are a favorite bait for fresh water fishermen. We have still not been able to discover the origin of the name Hellgrammite.

Letter 10 – Hellgrammite

Subject: Scary…ish bug? Location: Smithton, Pennsylvania May 28, 2013 9:47 pm Hi! Today, I was walking on a trail today (a chilly 29th May) and found two of these. After numerous searches, I’m at a loss as to what these are, because I was pretty fascinated by them. The trail is in Western Pennsylvania, nearby a river. There’s lots of woods around, and lots of streams and springs, and such – if that’s helpful. Thanks for your help! Signature: Z

Dear Z, This is a Hellgrammite, the larva of a Dobsonfly. We just postdated an image of a male Dobsonfly to go live on June 5 since we will be away from the office. We are going to postdate your Hellgrammite image to go live on June 6.

Letter 11 – Hellgrammite

Subject: what is this bug? Location: west central wisconsin May 31, 2013 4:29 am My son found this crawling up his garage wall. He said it was about 4 inches long, with many legs, and a very sturdy body. It resembles the pictures of the water Tigers but has many more legs. They just moved into this place which is right next to a river in west central Wisconsin and they’re curious to know if they’re going to be seeing more of these kind of bugs. Signature: bug identification

Congratulations on being introduced to a Hellgrammite. These semiaquatic nymphs are usually found not far from water, so the river you mentioned is most likely its origin. Hellgrammites eventually metamorphose into fearsome looking, but perfectly harmless Dobsonflies.

Letter 12 – Hellgrammite

Subject: river bug in Iowa Location: Winnebago River, Mason City IA June 9, 2013 11:32 pm We saw several of these bugs along a river trail today after very heavy rainfall and slight flooding. Any idea what these are? Signature: Elizabeth Haag

Hi Elizabeth, This is a Hellgrammite, the semiaquatic larval form of a Dobsonfly. For years, we have been trying to uncover the origin of the name Hellgrammite, but alas, our searching has not proven fruitful. We are also hoping to eventually be able to post a photo of a pair of Dobsonflies mating.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.