Dobsonflies are large, fearsome-looking insects, so if you have spotted one around your house, here’s everything you need to know about the Dobsonfly bite.
The Dobsonfly is one of the largest insects in the world (males can grow up to five inches long), and has a menacing look enough to scare even the most ardent of insect lovers.
This insect is found all across North America, but it’s really the larvae of the Dobsonfly, who you are likely to meet more because the adults hardly live for about a week.
Their larvae are called hellgrammites, and these are aquatic insects that hide under rocks in rapid waters. They are equally hellish-looking creatures.
But their aggressive features belie a simple fact: these bugs are not dangerous to humans. And if you have come here to understand the ill effects of their bite, let us say upfront that there are none.
But let’s talk a bit more about Dobsonfly, their unique features that make them look like something from a horror movie, and why those features have nothing to do with biting.
What Do They Look Like?
Perhaps the key reason behind the notoriety of the Dobsonfly is how they look.
The males sport large, one-inch sickle-shaped mouthparts in front, which look like tentacles. They also have two long antennae spread perpendicular to their bodies.
These long mouthparts are actually not as dangerous as they look – they are not very useful for fighting because they lack leverage.
Their real purpose is not to fight; they are useful during mating. The male grabs the female with these long mouthparts during sex.
Female dobsonflies have short but sharp protruding jaws. These are actually more dangerous because they can bite. The bites are quite painful.
Both the male and female have large veined wings that cover their entire bodies and are slightly overlapping in the middle when closed. Both are taupe-colored insects, and they have small white dots on their wings.
What Do Their Larvae Look Like?
Dobsonflies spend most of their lives as larvae, and these larvae (called hellgrammites) are aquatic. They live in rivers and hide under rocks.
Hellgrammites look like flattened centipedes and are usually colored either black, brown, or tan so that they can easily hide against the rocky background.
Hellgrammites have their own set of pincers, and just like the female Dobsonfly, they are painful biters.
They have three pairs of legs on the thorax and eight pairs of appendages on each side (which look like more legs). These appendages have a hairy tuft at the bottom.
Hellgrammites have adapted to their environment of rapidly moving waters by developing another hooked appendage at the tip, which acts like a claw to prevent them from getting swept up in a strong current.
Are Dobsonflies Dangerous?
Dobsonflies are not particularly dangerous to humans, and at least the adult dobsonfly male does not bite.
Adult females can bite, and so can their larvae, the aptly named “hellgrammites.” Both their bites can be painful. But on the whole, these bugs are quite harmless to us.
Dangerous To Other Insects
Dobsonflies begin their lives as aquatic creatures, and their larvae are one of the most voracious predators of insects found in their surroundings.
They are quite large, anywhere between two to three inches in length. But what’s more, is that they are not afraid of attacking anything – they even eat up small fish!
You will find these larvae in those parts of rivers that are near the mountains, or at least in sloping plains where the river runs very fast. Hellgrammites often hide under rocks in these bodies of water.
They use their hiding pace to their advantage, snatching up unsuspecting prey as it floats past them. They also hide from predators such as bass under these rocks.
Dangerous To Humans
If you look at the physical characteristics of the male and the female Dobsonfly, you might be forgiven for thinking that the male is more menacing.
Males have long (up to an inch!), fleshy mandibles protruding from their mouths, giving the impression of elephant tusks ready to impale anyone trying to hurt them.
But these large mandibles are pretty much useless in a fight because they can’t bite anything!
Females have short, sharp mandibles, and those do bite. If you try to place a female on your hand, get ready for a swift and sharp pincer attack.
It is best not to mess around with the females because their painful bites would leave you with a big rash.
Lastly, when you are in and around water, try to stay away from rocks. Hellgrammites can bite just as well as the Mumma dobsonflies, and the pain isn’t any lesser.
Their bites can pierce the skin and cause minor bleeding, so if you get bitten, you should thoroughly wash the wound and apply some antiseptic to it.
Should you be worried about meeting dobsonflies?
Your chances of meeting a real Dobsonfly are actually quite bleak; if anything, you should beware of their larval stage, the hellgrammites.
Dobsonfly life cycles are quite inverted – they live two or three years as larvae, but when they finally emerge as adults, they only have about a week left to live.
The purpose of a Dobsonfly’s life is actually just to mate – they don’t even eat for their short time on earth. They just mate and then lay eggs so that the next generation can continue living.
You will only find Dobsonfly near your home if there is a source of rapid waters running nearby, like a river.
They are nocturnal creatures and are attracted to light, so if you leave the outdoor lights on, you might find some of them flying around.
Dobsonfly: Are They Poisonous?
No, dobsonflies are not poisonous or venomous. As we said earlier, the females and larvae of the species can bite if you attack or try to handle them. But apart from that, they don’t cause us any harm.
How Do Dobsonflies Attack?
Simply put: they don’t attack humans. Dobsonflies are not interested in humans or biting or drawing blood or anything like that.
After all, if you only have a week to live, would you be interested in fighting creatures fifteen times your size? Their entire purpose in life is to mate and reproduce.
If you try to handle a female Dobsonfly roughly or place it on your hand, it might bite. But honestly – it is you who are to blame in that situation!
How Do Dobsonflies Fight?
Many people think that the large, sickle-shaped pincers at the front of the male Dobsonfly’s mouth are meant for fighting other flies.
The truth is these large mandibles are not useful in a fight except as a defense mechanism.
Moreover, the flies don’t fight each other over food or resources – they fight to win over the ladies.
The male Dobsonfly’s mandibles are actually evolved to attract females – as in, gee look, what big mandibles that guy has!
Females tend to pick the ones with the bigger mandibles. Unfortunately, size does matter even in the insect world, folks.
Dobsonflies are harmless creatures, and as long as you don’t go around poking your hand in their face, they are not going to come and bite you.
In fact, a Dobsonfly sighting is a bit of a unicorn because these bugs hardly live for 3-7 days. If you live near a running stream and keep bright lights on at night, you might see some of them.
Thank you for reading!
Considering what the dobsonfly looks like, there is no surprise that many of our readers have written in asking what this bug is over the years.
Go through some of these emails – while some are concerned, others are almost comical!
Letter 1 – Dobsonfly
I took this picture this morning on May 11, 2004 at 8 am. We had 3 of these bugs on our screen door. I have searched online for an answer and came up with nothing. These bugs were about 1 1/2 to 2 inches long, in the picture you can see my 9 year old daughter’s fingers to compare size. We live in New Jersey.
Hi Lori, You have a female Dobsonfly. The males have much larger jaws. Adults can get considerably larger than your specimen. We have an entire page devoted to them on the www.whatsthatbug.com website. Just click the dobsonfly link on the left side of the page in the alphabatized list for more information.
Thank you very much for clearing this up for me. I had no idea what this was. Thanks for replying so quickly!
Letter 2 – Dobsonfly
Male Dobsonfly in NE Pennsylvania
This Dobsonfly landed on a screen window on July 26, 2008 – showing the UNDERSIDE (since it was outside the screen). I was able to identify this as a male – because of your excellent website…. It truly was a fearsome looking creature. I used to fish the Susquehanna River for bass using hellgramites, which would sometimes nip a finger as we gathered them from beneath the rocks. I never realized that they would grow up to look like this.
Thanks for providing our website with an interesting perspective on this male Dobsonfly.
Letter 3 – Dobsonfly
Giant Assassin Bug with large pinchers? June 5, 2010 Ok, found this bug in our barn at Sealy, TX today. We do have cattle that go in there regularly and not sure if that helps. When I picked it up behind the head, it was snapping its pinchers and trying to possibly get me with its tail as well. To me it looks like a cross of a praying mantis and a large beetle with pinchers. I have it in a bug container, but not sure if I want to let it loose. Adam Sealy, TX Hi Adam, This male Dobsonfly is unable to use his formidable looking mandibles to bite humans. The female Dobsonfly on the other hand, with her much more utilitarian mouthparts, is quite capable of biting. We have heard that the male uses his saberlike mandibles to complete for a female, or in the mating process, but we have yet to see visual documentation of that claim. Neither the male nor female Dobsonfly feeds as an adult.
Letter 4 – Dobsonfly
A Dobsonfly June 14, 2010 Hello, We adopted this beautiful bug over the weekend camping trip. It looked like he was just coming out of a cocoon or ground. his wings were still moist and he could not fly yet. My daughter named him Larry the Lacewing. I checked your site today only to discover he was not a lacewing but a Dobsonfly. This one has a yellow head and mandibles. We found another the next day with brown head and mandibles. Feel free to use the images to show scale. They’re huge! How you want your letter signed camping along the Delaware Barryville, NY Your photos are awesome. Comment: For the Love of Dobsonflies June 14, 2010 Dobson Flies!!! I am SO excited to see all the dobson fly images being posted recently! About 5 years ago while I lived in Ohio, I came across a male dobsonfly which, not knowing what it was at the time, sparked my interest in the bug world! I have not seen one in person since my sighting 5 years ago, and look forward to the day I come across this magnificent creature again! Since there seem to be SO MANY sightings this year, maybe this is a good sign that I will get my chance! I live in Cleveland Mississippi now, about 2 hours south of Memphis, TN. Do you think I will be able to find one around these parts? Thank you for all the wonderful images, and the great work you do on this site! Cassie Shaw Hi Cassie, Thanks for your enthusiastic letter. Various species of Dobsonflies are found around the world. According to BugGuide, sightings in Mississippi occur … . Hold that thought since BugGuide is not currently available online.
Letter 5 – Dobsonfly
what is this bug?!? kinda freaky. Location: austin texas September 3, 2010 6:13 pm i found this out side my house its really big and scary what is it and can it hurt you? it was alive the other night and i just found it dead out side. signature: chelsi Hi Chelsi, Though they look quite dangerous, Dobsonflies are actually quite harmless.
Letter 6 – Dobsonfly
weird very large bug i found in fl Location: norther fl February 27, 2012 6:02 pm i have never seen anything like this. im sure it came in on some shipment from another country. it has a very large ant like head with large pincers. a body kinda like a moth and with that looked like dragonfly wings except that they were way thicker they could bend with out breaking. on top of it in the pic is a worm cuz my friend wanted to use it for fishin. please help me identify this crazy thing Signature: Larissa Hi Larissa, This is a female Dobsonfly, and it is a local insect for you. Interestingly, the larvae, which are known as Hellgrammites, are a favorite bait for fishermen. i found out what it was its a Dobsonfly
Letter 7 – Dobsonfly
Subject: Winged Insect-A Moth? Location: Northeast Florida March 16, 2013 10:32 am I took this picture in February. The insect was in my Oak tree which is dying. I thought perhaps it was the cause. Can you tell me what it is? Signature: PJ Bell Dear PJ Bell, This Dobsonfly has nothing to do with the death of your tree.
Letter 8 – Male Dobsonfly
Subject: duson fly ? Location: blakeslee ,pa July 19, 2014 2:59 pm Hi i live in northeastern pa . I found this bug outside of my work on the wall and was wondering what it was? Many people were freaking out over it because of the way it looked and its size. It was about 5 inches long . Never saw one before. Signature: lordnikon Dear lordnikon, Though you have the spelling wrong, you are correct that this is a male Dobsonfly.
Letter 9 – Bite of female Dobsonfly draws blood in Costa Rica
Subject: Flying cockroach Location: Costa Rica May 13, 2015 5:15 am This bit me on finger. Drew a lot of blood Signature: Jeff Dear Jeff, This is a female Dobsonfly. We have always stated that though they are harmless, the mandibles of a female Dobsonfly are quite strong and they might draw blood. Thanks for the confirmation. Male Dobsonflies have much more specialized mandibles, but they are incapable of biting. Perhaps the females have developed more defense mechanisms to protect them as they lay eggs. Larval Dobsonflies, known as Hellgrammites, are also capable of biting.
Letter 10 – Dobsonfly
Subject: large winged insect Location: Minneapolis, MN June 25, 2016 10:38 am found resting in large service berry tree. Insect is about 4 inches long, not including antennae, wings being most of it. Signature: JoanneK Dear JoanneK, This is a Dobsonfly, a species that exhibits strong sexual dimorphism, so it is easy to tell the sexes from one another. Male Dobsonflies have spectacular mandibles while female Dobsonflies have more practical mandibles, however the head of your individual is obscured by leaves making the distinction more difficult. In our opinion, it appears this is a female Dobsonfly.
Letter 11 – Male Dobsonfly
Subject: Never in 55 yrs Location: New Braunfels Texas June 28, 2016 4:06 pm Seen a bug that has the head of a beetle the body and wings of a dragonfly with the torso of a worm. Oddest bug I’ve ever seen in my life bar none. Have a pic if there is a way to upload Signature: Willie cheaney We are guessing a Dobsonfly. Please submit images using the Ask What’s That Bug? link on our site: I Googled your guess you guys are good. Ya’ll nailed it. Odd looking critter isn’t it I’ll drop Please submit a location.