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.

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