Dobsonfly Defense Mechanism: Explained

How do dobsonflies ward off their predators? Does their large size keep others away, or do these insects also fall prey to bigger animals and bugs? Here are some interesting dobsonfly defense mechanisms that are unique to them.

The Dobsonflies are one of the most fascinating aquatic insects, with over thirty species found in North America, Canada, and Mexico. 

These large creatures (some of them can grow up to five inches) with scary-looking pincers on their front can be enough to make you run away from an average Dobsonflies. 

But in their natural habitat, how do they protect themselves? In this article, let us explore the life and behavior of the Dobsonflies. 

Dobsonfly Defense Mechanism: Explained

Dobsonfly Defense Mechanisms

Like any other type of insect or animal in the wild, Dobsonflies have a wide range of special defenses against predators. 

These creatures are built differently, with pincers, jaws, and wings that help them survive and keep natural hunters away. 

Their Large Mandibles

The first thing you will notice about adult male dobsonflies is their large mandibles in front of their head. These are shaped like sharp sickles. 

These mandibles are used during mating or as a defense against other males. The mandibles make up almost the whole head and can grow up to 1 inch in length

Adult males have mandibles larger than females. They use these to attract and hold the females during mating. However, these are not powerful enough to pierce animal skin. 

On the other hand, the mandibles of the females are short and sharp. These do not contain any venom but are enough to inflict painful bites on predators, including unsuspecting humans.

Dobsonfly Defense Mechanism: Explained

Foul Odors

Dobsonflies have a chemical defense to their advantage, common to many other insects. 

The insects have Malpighian tubules as part of their excretory system, which releases a foul-smelling anal spray. 

This mechanism is often used as a last resort to ward off their enemies. 

Their Size

Humans, as well as animals, are intimidated by the large size of these creatures. For natural predators of the Dobsonflies, their size itself becomes a defense mechanism. 

These insects can grow up to 5 inches long, with a wingspan about twice the size of their bodies. 

The larva of Dobsonflies, commonly called Hellgrammites, also grows between 2-3 inches

These insects are considered one of the largest insect predators in the water, eating worms, different types of flies, and small fish. 

The size of Dobsonflies is one of the reasons that most predators stay away from hunting them. 

Hellgrammite Defense Mechanisms

Hellgramites are the larval form of Dobsonflies. These are comparatively smaller than adults but are still one of the largest aquatic insects. 

The larvae have their own defense mechanisms, which are effective in protecting themselves from their predators. 

Dobsonfly Defense Mechanism: Explained

Eggs laid out like bird droppings

Birds are one of the major predators of Dobsonflies and Hellgramites, so the insects have found a unique way to protect themselves in plain sight. 

Dobsonflies lay eggs in clusters, arranged in three layers, and the mass is covered by a clear fluid that turns white over time. 

The eggs resemble bird droppings which most birds or predators ignore. Therefore, making it the perfect hiding spot for the eggs and newly hatched larvae. 

Sharp Pincers

Hellgramites resemble adult Dobsonflies in terms of the structure of their mouth. These insects have very sharp mouthparts that can easily pierce the skin of animals. 

Like adults, the male larvae do not have sharp pincers to pierce. Female hellgramites have pincers that can pinch, cause painful bites to animals, and even draw blood. 

Frequently Asked Questions

Can a dobsonfly hurt you?

Yes, there is a chance that female dobsonflies can hurt you if you handle them incorrectly.

These insects have sharp pincers that can pierce the skin of humans and animals. 

Female dobsonflies are the only ones that have these sharp mandibles, however, and can cause painful bites. The males cannot do it.

Dobsonfly Defense Mechanism: Explained

How does the dobsonfly fight?

Dobsonflies use their large mandibles if they have to defend themselves against other potential mates of their love interest. 

For females, the mandibles are the greatest defense mechanism they have. They use these to keep away any threat and pierce the enemy, causing painful bites. 

What do dobsonflies turn into?

Dobsonflies are the final life cycle of the insect. They hatch into larvae called Hellgramites which live underwater for two to three years. 

After pupating for a brief period, they hatch into winged insects called Dobsonflies. The adult dobsonflies live for only about a week, and their only purpose is to mate and produce their offspring.

Why dobsonflies are called hellgrammites?

There is no specific answer to the etymology of Hellgrammites. 

Historically, fishermen are known to call aquatic bait hellgramites. 

These insects are used to this day as effective bait to catch fish. However, the origin of their names is unknown. 

Wrap Up

Whenever we find a scary-looking insect, our first resort is to get them out of the way and avoid them. It works as a defense mechanism against something we consider a threat. 

Similarly, a threatening appearance or chemical release is the defense mechanism for creatures like the Dobsonflies. 

The important thing to remember is that it is all part of nature’s fascinating way of protecting every creature in its unique manner. 

Thank you for reading, and look out for bug bites around the water! 

Reader Emails

Many of our readers have reached out to us to learn about the defense mechanisms of the humble dobsonflies over the years.

Read the emails below to understand the interest.

Letter 1 – Another Dobsonfly Pupa

 

what is this?
I live in Elkhart Indiana ; I found this in a park in Goshen Indiana & I couldn’t find anything on the net about it, what could this be. Obviously it dead, we couldn’t keep it alive. I like your site, keep it up.
Joe McKalips



Hi Joe,
This is the second Dobsonfly Pupa photo we got in two days. It is dormant and will emerge, probably very soon. The adults are quite frightening looking.

Letter 2 – Another Dobsonfly Drawing?

 

Can you tell me what this bug is?We saw it approx 10 yds from a river,in central Minnesota.Someone said maybe a water scorpian,but the pictures of water scorpians I saw,were different than this.This has a more slender body,light grey in color,and the pinchers were short.I did not notice any sort of tail on this one?Thanks~
Mary Hoeper



Hi Mary,
We believe your fabulous drawing and descriptive text is representative of a Dobsonfly, probably a female.

Letter 3 – A Pair of Dobsonflies

 

Pair of Dobsonflies!!! (06/29/2005) What type of bug is this? Hi. I was wondering if you could help identify these bugs for me. I live in the Poconos region of Pennsylvania, about 45 miles west of Scranton. Based on the difference in body sizes and how the pinchers look I’m guessing that they’re most likey a male and a female. The one with the long crossed pinchers is about four inches long (from the end of the wings to the end of the pinchers), with two inch antennae and one inch pinchers. The one with the short pinchers is about three inches long, with one inch antannae and maybe 1/4 inch pinchers. They’re both very docile and didn’t try to fly away when I had them in the tupperware with the lid off. Thanks! Ben
A Pair of Dobsonflies
A Pair of Dobsonflies
Hi Ben, We have been getting plenty of Dobsonfly photos lately and when they are in season, we always try to keep a photo on our homepage. We currently have several that you would have seen had you scrolled down a bit. Your photo is exquisite and will have a permanent spot at the top of our Dobsonfly page. Your are correct in that they are male and femaLe of the same species and the male has the long mandibles.

Letter 4 – Andean Dobsonfly from Peru

 

Winged bug on our yard August 19, 2009 This morning my boys found this winged bug crawling on the grass. We know it must fly because of it’s wings, but it has just been crawling around. We found it in the morning just after the sun came into the yard. It appears to have pincers on its head and rears up when we get near it. Any help would be great! Thanks! Stacey Abancay, Peru (Andes mtns-approx 8,000ft)
Dobsonfly from Peru
Dobsonfly from Peru
Hi Stacey, If you run into our co-workers from LACC, two hot American college professors named Sharon and Naima who are vacationing in the Andes, please say “hola” for us.  This is an awesome looking Dobsonfly in the family Corydalidae, but we haven’t a clue what species it is.  We suspect it is a female Dobsonfly as males have much more formidable mandibles.
Dobsonfly from Peru
Dobsonfly from Peru
Your photos are all so dramatic, we are going to post all three.
Dobsonfly from Peru
Dobsonfly from Peru

Letter 5 – Dobsonfly

 

Is It as dangerus as it looks? March 11, 2010 My 8 year old Neice came running to get me because she found a “big and scary bug” this is what was sitting just out side the door. We live in central Missouri, in a small farming town lots of rural farm animals like chickens and goats around. Nither myself nor my naighbors have seen a bug like this before. this was about mid august. i have shown the pic around and one of my friends mentiond this web site to me. the pincers were functional but they looked rather soft and like it couldn’t realy pince with them. needles to say we didn’t get close enough to find out. It was about 3 to 4 inches long and i only got one shot becuase my flash spooked it and it flew away. not far but into the near bye tree and out of camara range. Is it native and is it dangours? and what is it? K.Ekstam Eugene Misssouri
Male Dobsonfly
Dear K, This is very early in the year for a Dobsonfly appearance in Missouri, and even the data on BugGuide indicates that the earliest sightings for the year have occurred in April in South Carolina.  This has us a bit puzzled.  The Dobsonfly is native and harmless.  Your specimen is a male, and the mandibles of the female are considerably smaller, but also much more capable of inflicting a significant pinch, though again, it is perfectly harmless.  We are also confused that your letter requests an identification, yet the photo file is titled “Dobsinfly male”. Im sorry about that. the picture is not recent it was from last summer.i thought i had mentiond that. i had stumbled on your web page a few days ago and  asked my husband were the picture of the big creepy bug was. he said he had a copy put up on our deviant art web page cause it was a good photo, it wasn’t untill after i sent it to you that i realized he already knew what it was. i feel a little silly about that. but i hope you enjoyed the picture at least. and that you for the bit more information on 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.

Letter 1 – Hellgrammite

 

Larvae found in basement
I don’t know what kind of larvae this is but I never saw one quite so big. He is about 4 inches long and about ? inch thick. I live in South Central Pennsylvania USA. I am near water if that helps. This guy was crawling along my basement floor and I thought maybe you would know what he turns into or what he is? Thanks,
John



Hi John,
You have discovered a Hellgrammite, the larval form of a Dobsonfly.

Letter 2 – Hellgrammite

 

Okay, this bug was huge!! What is it?
Hello!
I saw this critter on the side of the Virgin River in Zion National Park in southwestern Utah, heading for the water. What is it? Unfortunately, my picture came out blurry, and I didn’t put anything in the pic for scale, but he was about 4-6 inches long. My coworker guessed it was a beetle larva. Thanks!
Sarah



Hi Sarah,
This is a Hellgrammite, the larva of the frightening looking, but harmless Dobsonfly.

Letter 3 – Peruvian Hellgrammite

 

weird bug
Hi I took a picture of this strange bug in southern Peru (near Machu Picchu). My professor says it is a rove beetle, but I think it moved in an "inch worm" fashion, so I am not convinced. What do you think?
Heather



Hi Heather,
We would love to know what the locals in Peru call the Hellgrammite, the larva of a Dobsonfly.

Letter 4 – First Hellgrammite of the Year!!!

 

What the heck?
This is a picture of a bug that we found while camping in west Georgia. We found 3 of these creepy fellows and not really sure what they are. It looks like they have six legs, and several other spikes pertruding from their body behind their legs (at first it looked as though they had 20 legs).



This is our first Hellgrammite photo of the year. The Hellgrammite is an immature Dobsonfly and a choice bait for fishermen.

Letter 5 – Emily's Hellgrammite Metamorphoses into Pupa

 

Active Dobsonfly Pupa
Hello again, Bugman!
I decided to keep my hellgramite. It is enjoying its indoor pupal chamber quite well. It has begun to pupate, but becomes very active when I lift the flat rock it’s under to check on it. Do you think it will hatch into adulthood before winter hits? Thank you!
Emily



Hi Emily,
Thanks for sending us documentation of your Hellgrammite’s metamorphosis. We aren’t really sure how long the pupa stage lasts.

Letter 6 – Hellgrammite

 

Hellgramite
Hello again, Bugman!
I found this beauty today. My first hellgramite, and about three inches long. It was in a pupal chamber in sandy soil, under an overturned card table near the Missouri River. It copped an attitude pretty fast when I tipped the table up (I was hoping for a snake!). Anyway, I noticed you didn’t have any hellgramite photos on the page. I’m sorry the lighting is so bad. I decided to put it in a bowl of water for one shot, to get some of the sand off. I think I’ll let him go tomorrow. Thank you,
Emily



Hi Emily,
Long, long ago when we set up our website, we created separate pages for the larval Hellgrammites and the adult Dobsonflies. You can find other Hellgrammite images on their own page.

Letter 7 – Hellgrammite

 

please identify this bug
Please identify this bug. We saw it on a bike path next to the New River in Virginia today.
Ashby Hopkins

Here are more pictures. I thought it might be a Coach Beetle at first, but it did not have long antenae. Thank you,
Jim Hopkins



Hi Ashby and Jim,
This is a Hellgrammite, the aquatic larva of the Dobsonfly. The winged adult males have frighteningly large mandibles, but they are docile and harmless. The females, on the other hand, will use their smaller mandibles to bite, but a harmless pinch is all that will result.

Letter 8 – Hellgramite

 

What is this bug??????????
Found in an old building situated next to a stream!!! I’ve never seen anything like this……… What is it???
Greg in NJ



Hi Greg,
This is a Hellgramite, the larval form of the Dobsonfly and favored bait of fishermen.

Letter 9 – Hellgrammite

 

A bug I caught
Hello,
My name is Josh, I will attach a picture of a bug that I found this weekend while walking down the side walk, it was in the area of Ceder Falls Iowa, I was with in less than a 1/4 mile of a river and the area I found it in is a little bit swampy as well, I am wondering if you could tell me what kind of bug it is? the first picture of it is sitting on the ground, the next it is hanging from a stick by it’s jaws, in the second picture of it you can see the bottom of it, thanks again, and I’ll await your response,
Josh



Hi Josh,
The Hellgrammite is the larval form of the equally fierce-looking, winged Dobsonfly.

Letter 10 – Hellgrammite

 

What kind of bug is this? I found many of these bugs shortly after it rained in North Georgia. I was on a camping trip and I would like to know what these are. Thank you David Hi David, This is a Hellgrammite, the larval form of the Dobsonfly. They are prized bait for trout fishermen. Update from David Gracer www.slshrimp.com Hellgrammite Dobsonflies are classed in the order Neuroptera. The larvae, hellgrammites, are not only by fisherman as bait, but are also highly regarded as food in some places (mostly Mexico and South America). The larvae are found under stones in streams, but of course they’re well-equipped with pain-inducing pincers. Although these are among the most fearsome-looking of all the edible insects I’ve seen, page 157 of the excellent book Man Eating Bugs: The art and science of eating insects displays a picture of a little girl in Peru holding a large hellgrammite

Letter 11 – Hellgrammite

 

Menacing Bug
My kids and I found these bugs in a damp, walking tunnel in Central Wisconsin. They were 3-4 inches long and had big, sharp pinchers that they used violently to defend themselves. They are very prehistoric looking. My guess is that it is some type of larvae. What are these, and are they usually lightning fast and deadly poisonous (LOL)?
Thank you,
Tom Curiouski



Hi Tom,
If you think the Hellgrammite is frightening, you should see the adult male winged Dobsonfly. Both larvae and adults are harmless. Hellgrammites are a choice bait for fishermen.

Letter 12 – Warning to Fishermen!!!!!!!

 

Hellgramites
Hello,
I know I just emailed you about a wasp but I was reading your hellgramite section and was thinking that you might think of warning novice fisherman about those pincers. My husband and I love to fish (he handles the bait… yes I am too squeamish, and in the case of hellgramites, I am afraid of being pinched!). Whenever we catch hellgramites for bait, he always takes a pair of pliers and snaps off the business end of those pincers before attempting to use them as bait. He neglected to do so once… I have never heard him yell so loud! I laughed so hard I could hardly fish (at the time it was hilarious). I thought that people who aren’t familiar with using hellgramites as bait but would like to try it might want this useful tidbit of information.
Mande Hyre

Letter 13 – Hellgrammite

 

the strangest bug i’ve ever seen in my life!
I was hiking at McConell’s Mills in Western Pennsylvania and happened across this bug sitting in the middle of the street. It appears to me to be some sort of beetle larva, but it’s SO big. It also had this fancy move it did when we touched its head with a stick – it would curl its tail under [which was soft like a catepillar’s body] to quickly launch itself backward a few inches. Here it is pictured with my boyfriend’s finger [who, for scale, is 6’4″]. And here is another better picture of its face. I also have a video i took of it walking and doing its cool backwards launch maneuver, which you can have if you’re interested. PLEASE tell us what kind of bug this is. We’re absolutely dying to know. I almost regret not taking it home with me! I just hope it didn’t wander back into the middle of the road. Thanks!
Jen and Glenn
ps. We also found a bunch of these really pretty red and black millipedes, which i’ve included a picture of. They were about 4 inches long.



Hi Jen and Glenn,
You have just encounted a Hellgrammite, the larval form of the Dobsonfly. These curious larvae are prized by fishermen as bait.

Letter 14 – Hellgrammite

 

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,
He is beautiful. He is an adult Dobson Fly, the larvae of which are known as Hellgrammites. The male has the formidable 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 15 – Hellgrammite

 

Hi, My girlfriend and I stopped to get gas in Connecticut, when I got out to start pumping I noticed this thing… slowly crawling around. It was between 3 and 4 inches long and moved rather slowly. Six legs, large ant-like head but a centipede like body. No antannae but large mandible looking things. We looked around and there were about 10 or so of them roaming around in various parts of the gas station lot. I came home and did some web searching trying to figure out what it was but was quite unsuccessful. The closest similiar descriptions I have found seem to be of the Protura order, but they are typically very small, and the bug I spotted did not have a cone shaped head. I came across your site and went through the bugs featured on it, with no luck. I returned after my failed web searches to snap the above picture, it had stopped raining, and this was the only one I could find.
What is this thing? Michael

Dear Michael,
Definitely a Hellgrammite, the larva of the Dobson Fly. We have photos of adults on our site, and would love to post your photo with the letter. I just received another letter from someone who spotted one at her cabin in Virginia, but I had no image to show her.

Letter 16 – The Creatures

 

Hello Bug Person,
I saw your site and thought maybe you could help me and my roommate out. We have creatures. That’s what we call them, because they are unlike anything we’ve ever seen. In the last three places we’ve lived, we have seen the Creatures in our basement. They are similar to centipedes in that they are long, have many legs, and are creepy. But that’s where the similarities end. Centipedes are flattened with legs that look like this ^ with one joint, but these Creatures have 2 joints, like spider legs. They don’t have as many as a centipede but definitely more than 8. The legs are generally the same size too, not different lengths like a house centipede. they don’t have the front "fangs" like a centipede but a mandible similar to a spider’s – no antenae no little butt feelers. And they come in 3 different colors. I’ve seen very large ones (4-5 inches), black with white spots; others were just as big but dark brown; and just the other day, in our new duplex, we found a little one maybe 2-3 inches long and light brown. They are very fast and i even hit one with a book, cutting off its lower half, and the rest of it got away. Yeah, these things are evil. Nobody knows what these things are. We’ve had hunters, floridians, Arizonians, and other self-proclaimed bug experts, but we always get the same thing: a hideous blank stare and lonely nights in our basement. Can you tell me what the creatures are?

Alex,
Be afraid. Be very afraid. Scream Alex, scream for your life. You have Tinglers living in your basement. Barring the possibility that the horrific monster from the 50’s horror flick starring Vincent Price is in your basement, following you from house to house, I can think of several additional possibilities, though none seems to exactly fit your description.
Possibility #1 is the hellgrammite, the larval form of the dobson fly. These four inch long creepy crawlies normally live in or near streams, but we have heard reports of them being found in basements. Check out this website to see if the hellgrammite is your culprit. http://www.watersheds.org/blue/nature/gallery2/
pages/hellgramite.htm

Possibility #2 would be a sun spider or wind scorpion from the family Solpugidae. They move quickly, and can be found in basements, though I haven’t heard of any American species quite as large as the creature you describe. They are closely related to other arthropods called vinegaroons.
Possibility #3 would be a different type of centipede. Scolopendra polymorpha is a six inch long species of centipede that resides within the continental U.S. You can locate a photo of it and of the sun spider on this website. http://www.angelfire.com/oh2/USInsects/
Arthropods.html

I shudder to think that we here at What’s That Bug have entered the ranks of hunters, floridians or Arizonians with blank stares, but without more concrete information, perhaps a photograph or a drawing, and some hint of your coordinates on the globe, we’ve run out of possible id’s.

Several months back, this column tried to identify a bug based on an inquiry from Deb. Here is her letter:
Hi,
I almost had a heart attack last week as I saw the biggest bug I have ever seen! I work as a therapist in an upstate New York School. My office is in the basement. As I rounded the corner to answer the phone, something huge
was slowly crawling across the doorway on the floor. It was blackish grey, about 4 inches long with a flattish body. The head looked as large as my thumbnail. It appeared to have short spikey hairs on its body, and 6 legs protruding from its middle segment. The abdomen was very large and trailed behind the legs. I didn’t notice any antennae, but it may have had pincers on the mouth. Thank God for a brave custodial worker!!! Later in the day, another co-worker said that he collected those bugs for trout bait, and that they sprout wings and fly around. Please! That was the stuff of nightmares!!!!!!!! I swear that I have seen miniscule versions of this bug in my own yard and want to know if they are the same. Could I have these prehistoric monsters flying in my back yard???!!!
—Deb

Embarassingly, I misidentified the culpret as a large roach. It turned out, in fact, to be a hellgrammite, the larval form of the dobsonfly, which you have photographed. Locally, the California Dobsonfly (Neohermes californicus) can be found near streams, generally at higher elevations, hence the frequent use of the larva as trout bait. The hellgrammites are aquatic and are found in swift streams where they prey on other insects, but they can pass dry spells under rocks and debris in the damp stream beds.
Dobsonflies are members of a primitive order of insects known as nerve-winged insects, which includes other oddities like the ant lion and lacewings. All adult nerve-winged insects, including the dobsonfly, are feeble fliers and are predaceous upon insect pests, so they are beneficial.

Letter 17 – Hellgrammite in Natural Habitat

 

Hellgramite in a hole Sat, May 23, 2009 at 8:07 PM Hello. My husband and I had a truck full of screened loam delivered for projects around the yard and it appears to be loaded with hellgramites! I looked at the hellgramite photos on your website and didn’t see any of them in their “natural habitat” (basically a hole in the ground), so I thought you might like this one. This one had burrowed into the ground under a brick that was holding a tarp down to keep the loam dry. Funny thing… we actually learned about hellgramites and Dobson flies a few of years ago from this website. Shortly after our move to our house along a small river in New Hampshire, we saw our first crazy, prehistoric-looking hellgramite on our driveway. We don’t typically notice that many of them, maybe a couple of hellgramites and Dobson flies a year, but we have seen dozens of them over the past few days as we have been shoveling and raking the dirt. PGF in NH Southern NH, Monadnock Region
Hellgrammite in a hole
Hellgrammite in a hole
Dear PGF, We are happy to be going strong and continuing to serve the curious after all these years.  We are greatly appreciative to be able to post your wonderful photo of a Hellgrammite in its hole.

Letter 18 – Hellgrammite

 

Big, Black, Shiny Bug Tue, May 26, 2009 at 10:11 AM We saw a number of these bugs by a river on the CT/MA border after a rainstorm in late May. They didn’t hesitate at puddles, but swam straight across and walked out on the other side. They were about 3 1/2 inches long, black, shiny, and had spines. They didn’t seem to be aggressive. What are they? Sandi Massachusetts
Hellgrammite
Hellgrammite
Hi Sandi, This is a Hellgrammite, the larval form of the fierce looking but harmless Dobsonfly. Hellgrammites are considered to be one of the choicest baits by many fishermen. We just recently posted another photo of a Hellgrammite in its subterranean burrow. Ha!  We thought they had a Dobsonfly like shape!  Thank you!  Our curiosity is satisfied…until next time! blessings!!!  Sandi

Letter 19 – Hellgrammite

 

What is this? Mon, Jun 22, 2009 at 9:39 PM My freind and I were camping in Algonquin Park for six day on the Petawawa River. On the second last night we came across this interesting looking centipeide? at around 9:30 in the evening. After following it around for a whille we noticed another one. We then paned the rocky campsite and saw may of these things crawling towards us. They all must have been about 4 to 5 inches in length and a half inch wide. As the next day went on we saw very few (2 or three of them)of there on our travels down river. When night approced that evening we saw them againg coming out in numbers. Thge only difference this night is that they were crawing all over my tent as I slept. At one point of the night I woke up and counted ten on my tent. It was deffenatly a very creepy ni ght! I am very interested to know what this is? Greg Noel Algonquin Park on the Petawawa River
Hellgrammite
Hellgrammite
Dear Greg, If your camping trip involved fishing, you missed an opportunity to stock up on one of the most prized of all live bait, Hellgrammites. Hellgrammites are the larvae of Dobsonflies. We have recently posted several images of Dobsonflies, so your Hellgrammite is a welcome current posting to our site. Your first-hand observations of the nocturnal wanderings of Hellgrammites is unlike anything we have ever read in a traditional entomology text, and as such, it is priceless.

Letter 20 – Hellgrammite

 

Please identify this weird bug for me. Wed, Jul 1, 2009 at 10:44 AM I was visiting my parents’ lake cottage in the Adirondack Mountains in mid-June and found this bug by the downstairs brick patio. It was raining heavily and he was just sitting in a dry spot. It was about 11 pm. I scooped him up in a dish and found 2 more of the same size in the same vicinity. It was very docile and didn’t freak out when I picked him up; didn’t try to strike or fight at all. He wasn’t affected by light or water. (I flushed his two friends down the toilet and they didn’t struggle at all when put into the water.) I put him in a baggie and took his picture with a measuring tape to show his size. I left him in the baggie hoping he would suffocate and I could keep his body to show people for identification, but he chewed through the baggie and disappeared. I went back to the area where I found him and his friends but haven’t seen any since. This is in a pine-y, wooded area next to a lake. Pine needles are more abundant than grass. The patio where he wa s sitting is made of brick pavers. My parents also have a jacuzzi tub on the same patio, but they were not next to it when I found them. I am at a loss, finding nothing online even close to this bug to compare. Help! Thank you for your assistance. Upstate New York, Adirondack Mountains, Lake Algonquin
Hellgrammite
Hellgrammite
You have found Hellgrammites, the larvae of Dobsonflies.  We really don’t condone flushing living things down the toilet.  Hellgrammites are semiaquatic and can survive total emersion for a period of time.  We would like to believe that the two individuals that were flushed will emerge unscathed at the end of the line, but that is probably just a fantasy.

Letter 21 – Hellgrammite

 

what is this? May 31, 2009 we were camping with our kids and found this under a rock around an old fire pit.. we went to another camp site and found 2 more there also in the fire pit.. It has 6 large legs under it and very strong pinchers. it was about 3 inches in length. we have never seen anything like this before and dont know if it is harmful or not.. cautious campers in the adirondack region of ny state
Hellgrammite
Hellgrammite
Dear cautious campers, This is a spectacular Hellgrammite, the larval form of a Dobsonfly.  We are sorry our reply took so long, but today we are randomly selecting from among our unanswered mail.

Letter 22 – Hellgrammites for Bait

 

Hellgrammites/Dobsonflies (Please Read) January 10, 2010 Hellgrammites can live completely submerged in water. They have gills all along there segmented bodies. They live for a few years in their larval stage. Then they come to land to pupate. They stay in their cocoon throughout winter only coming out to mate. They only live for 7 days as Dobsonflies. They mate, lay eggs and then die. During these 7 days the are thought to not eat at all. In there larval stage they are attracted to light because they are nocturnal. Just thought that I would give you a little info. I have been using these as fishing bait for around 15 years now. SW Virginia, Appalachian Mountains Thanks, Zelik
Hellgrammite
Hellgrammite
Hi Zelik, Thanks for your comment.  Recently a writer named Thomas requested permission to reproduce one of our Hellgrammite images for an article he is writing for an Angler’s magazine, and he has promised us that we may reproduce that text once the magazine is published this spring.  We are including a couple of Hellgrammite images from the past with your letter since you did not provide one.
Hellgrammites captured for bait
Hellgrammites captured for bait

Letter 23 – High School Science Experiment produces unknown Larva!!!

 

Subject: What is this bug? Location: Jamestown, Tennessee October 10, 2013 10:56 am I’m a high school senior this year and currently enrolled in a Biology II class. We recently did an experiment where we placed decomposing leaves in a mesh bag and let our leaf packs sit in water for three weeks. When we opened our leaf packs today, this bug was in our packet. No other group had anything like it, and our teacher could not identify it. Do you know what this could be? Signature: Alex
Unknown Larva
Unknown Larva might be a Hellgrammite
Hi Alex, Unlike your Biology teacher, we do not have a background in natural sciences.  We are very curious what this experiment was supposed to produce.  What kind of water were the leaf packs sitting in?  Was it distilled water or were the packs tossed into a lake?  Since the packet was under water, this larva must be aquatic.  At first we thought it was a Hellgrammite, but upon enlarging the thumbnail that was attached to the email, we realized that the appendages typically present along the abdomen of Hellgrammites, the larval form of Dobsonflies, appear to be absent.  The head of your larva does appear quite similar to the head on this Hellgrammite posted to BugGuide.  Perhaps one of our more knowledgeable readers will correct us, but we are still leaning toward this being a Hellgrammite.

Authors

  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

12 thoughts on “Dobsonfly Defense Mechanism: Explained”

  1. I live on the Delaware River and each year we have the hellgramites crawling up to our house, sometimes even in our house (we have found them in our bed).Someone left the screen on the slider open a crack. The way this man described the crawling is exactly as we see it each year, and then when they metamorphasis into the adult dobsonfly is a sight to behold, hundreds of these creepy critters flying in the night. As I write this letter I have a dozen adults on the side of my house. AS WE SAY EACH YEAR THERE HERE!!!

    Reply
  2. The mandibles are very megalopteran (like a dobsonfly or fishfly), but it’s difficult to decipher the appendages that should be at the end of the abdomen. Definitely need more info on the kind of water the leaf pack was placed in, where the leaves came from, etc. Megalopterans need oxygen from flowing water, so this critter may actually be an aquatic beetle larva of some kind, which can tolerate lower oxygen levels.

    Reply
    • Thank you for your input. We never received any further information, and we are still quite curious what this “experiment” was expected to produce.

      Reply
  3. Great info – thanks. We found a large female on our garage door – we live in Northern Virginia near DC. I remember a huge swarm of these on my grandparents farm in Monroe County, WV and also recall them when we fished at Smith Mt Lake, but this is the first one I’ve seen in the DC area. Our house backs to a Potomac River tributary with a dam but it does have moving water. Should we anticipate a large hatch of these coming out of the water this summer? Hoping not.
    Thanks again!
    Kristy

    Reply
  4. Great info – thanks. We found a large female on our garage door – we live in Northern Virginia near DC. I remember a huge swarm of these on my grandparents farm in Monroe County, WV and also recall them when we fished at Smith Mt Lake, but this is the first one I’ve seen in the DC area. Our house backs to a Potomac River tributary with a dam but it does have moving water. Should we anticipate a large hatch of these coming out of the water this summer? Hoping not.
    Thanks again!
    Kristy

    Reply
  5. looking to purchase hellgrammites, do you sell them and ship to places in wisconsin?
    what do you charge if you do sell and ship them?

    Reply
  6. looking to purchase hellgrammites, do you sell them and ship to places in wisconsin?
    what do you charge if you do sell and ship them?

    Reply

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