Dobsonfly Structural Adaptations: 9 Tips To Surviving in The Water

Dobsonflies live as aquatic insects most of their life and have uniquely adapted to their environment. Here are some dobsonfly structural adaptations and what benefit they derive from them

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Structural adaptations are one of the most amazing things about the world of insects. If you’re fascinated by how different insect species adapt to their environments and life cycles, this article is for you. 

Let’s check out what structural adaptations you can find in a dobsonfly, which, by the way, happens to be the largest aquatic insect in the world.

Feeding

1. Larvae Have Strong Mouthparts to Bite Prey

The most noticeable features of dobsonfly larvae are their large and strong mandibles. 

They are voracious aquatic predators that prey on other aquatic insects, larvae, and small fish. The strong mouthparts allow them to rip their prey apart.  

2. Use Touch and Chemical Sensing to Find Prey

As mentioned above, dobsonfly larvae are carnivores and hunt other aquatic creatures. 

They locate their prey using both touch and chemical sensing. However, they also have eyes and are at least capable of identifying motions and shadows.

3. Terminal Hooks To Hold Themselves in Running Water

If you look closely at a hellgrammite (dobsonfly larva), you’ll notice a pair of hooked appendages on its terminal end. 

These hooks serve an important purpose in their hunting technique. These larval insects mostly hunt in fast-flowing water, which means they’re always at risk of getting swept away in the current. 

These terminal hooks allow the ambush predators to hook themselves to rocks or other surfaces while it hunts or feeds.

4. Larvae Can Swim Both Backwards and Forwards

An interesting fact about dobsonfly larvae is that they’re capable of swimming both forward and backward by undulation. 

This further enhances their hunting capabilities by enhancing their mobility in the water. However, they don’t swim often – they mostly crawl along surfaces.

5. Adults Don’t Feed

The feeding habit of adult dobsonflies is quite contrary to the aggressive predacious nature of their larvae – they don’t eat any solid foods. 

While adult male dobsonflies don’t feed at all, the females sometimes feed on nectar from flowers. Not needing to feed is indeed a nice perk for these bugs.

Mating

6. Elongated Mandibles For Fighting

While hellgrammites use their strong mandibles to prey and feed, the winged adults have a completely different purpose for these appendages contesting for a female. 

Adult male dobsonflies grow elongated, sickle-shaped mandibles. They fight rival males by hovering over them aggressively and trying to grab and flip them using these mandibles.

Besides, female dobsonflies also find males with longer mandibles more attractive. This is another way how the mandibles help male dobsonflies gain the upper hand when contesting for a female.

7. Scent Glands and Touch During Mating

Like many other bugs, dobsonflies use scent to communicate with potential mating partners. There are scent glands on the abdomen of male dobsonflies that help them in mating. 

Touch plays a role in their communication and mating ritual too. Male dobsonflies place their mandibles on the females while courting them.

8. Nuptial Gifts

At the end of a mating session, a male dobsonfly produces packages of nutrient-rich spermatophores as nuptial gifts for the female. 

However, not all genera of dobsonflies produce nuptial gifts. 

The size of the packages is inversely proportional to the size of the mandibles. Dobsonfly species that boast the biggest mandibles produce the smallest sperm packets or do not produce them at all.

Breathing

9. Larvae Can Breathe on Both Land and Water

The larvae are aquatic, but that does not mean they cannot breathe on land. 

Their bodies are highly adapted to their aquatic habitats, and they’re capable of absorbing an abundant amount of oxygen from the water. 

They do this using the several tracheal gills they have on either side.

Here’s a quick explanation of how dobsonfly larvae breathe underwater. They have eight pairs of appendages on their sides, which resemble legs but have gill tufts at their ends. 

These feathery gills increase the surface area that the larvae can use to absorb oxygen. They also have a set of puffy gills similar to dandelions, which they can wave in the water to extract more oxygen.

But the unusual aspect is that, in addition to the gills, hellgrammites also have spiracles that they can use to breathe directly from the air when they’re on the surface. 

Their choice of habitat helps them in respiration – fast-flowing and shallow waters contain higher amounts of oxygen.

Frequently Asked Questions

Conclusion

If you live near a water body in North America, there’s a chance that you might encounter Eastern Dobsonflies in your home. 

Although it’s uncommon, these insects sometimes lay their egg masses in pools too. Finding dobsonflies in or around your home indicates a relatively clean environment, as these insects avoid polluted waters. 

Thank you, reader, and I hope you enjoyed reading about the amazing structural adaptations of these huge bugs.

Reader Emails

Dobsonfly larvae are extremely unique (and rather hellish-looking) creatures.

Over the years, readers who have found them near their homes have always come back with several queries about where they live, how they adapt to living in the water, and so on.

Read on to learn more about all the questions and answers.

Letter 1 – Dobsonfly for Dinner!!!

 

this bug… what is it?? Hi, I found this bug outside and it was dead when I found it. It was just so strange I put it in a container and too pics of it. I can’t seem to find anything like it on the internet. I put some pictures of it in the email, but here’s the facts you might not be able to tell by the pics. It has small eyes, 6 legs that are NOT bent back like a grasshopper… They’re all down and pretty short. It has a wierd pincher thing on it’s butt… I don’t know if that’s for mating or what. It has hard tusk like things coming off it’s face. I’m not sure if they’re antenna but then it has another set of antenna on its head. It has I THINK 2 sets of wings. I could only see 2 wings, but my cousin picked up the bug and said he thought there was another set of wings under the ones we can see. If you can help me PLEASE tell me what this thing is. If you’re not the one that can ID it, please pass it on to who can. Thank you very much, Andrea Hi Andrea, It is so daring of you to serve up this male Dobsonfly for Dinner before you even knew what it was and if it was edible. We already have the larval form, known as Hellgrammites, on our edible insect page, and now we will add your toothsome specimen to that page as well.

Letter 2 – Dobsonfly from Bolivia

 

Subject: Huge Bolivian Fairy Bug Location: Bolivia January 27, 2013 8:13 am This Bug was found in the Amboro national park in Bolivia and I need to know what it is. People there called it ’the Fairy’. Length about 12-15 cm. Thank you Signature: Kathrin

Dear Kathrin, This is a female Dobsonfly, and though we are quite certain it is a different species, we do have Dobsonflies in North America.  The male Dobsonfly is a fierce looking though perfectly harmless creature.

Letter 3 – Dobsonfly Courtship and Mating

 

Subject: Dobsonflies Doing the Deed! Location: Farmington, NY August 21, 2013 11:17 am Hi Bugman! I made a trip to Farmington, NY last month and witnessed the mating of two Dobsonflies. The male was on the front porch screen for a couple of hours, just hanging out and looking lonely. Low and behold, the ”lady of his dreams” arrived! He went right over to her, and they did a little dance for a minute – you know, getting to know each other. He eventually got down to business and they mated for about another minute. I watched the whole ritual and took lots of pictures. I’ve tried to upload 3 of them but it keeps hanging, so here is one. Let me know if you would like more. Thanks for all of your work on the site! Signature: Dobsonfly Voyeur

Dear Dobsonfly Voyeur, We would love to see more of your mating Dobsonfly photos.  Just responding to this email should allow you to attach a few.  We are especially interested in photos that document the actual mating activity.  It is fascinating that the male arrived first.  In most insects, the males are attracted to the pheromones released by the female.

Daniel – Great to hear back and thanks for the post on What’s That Bug!  I will attempt to attach 13 pictures to this.  In case the attachments get lost in cyberspace, you can view the pics on my Picasa site.  You are free to use these in any manner (download/post/share, etc).  You can also post the link for visitors of your excellent web site.  All of these were taken with a Samsung Galaxy S4, so the quality is good – but they are not high-quality macro lens shots.  Perhaps my next toy will be a nice digital SLR for events like this.  Thanks again, and glad that you are interested! Tim Wheeler

Hi again Tim, Wow.  We have had a call out for quite some time for photos of mating Dobsonflies and we are thrilled to get your documentation.  It will take us a bit of time to format all the images, adjust the image quality and post them, but we plan to make this a featured posting.  The actual mating was quite fast and we are very curious about the actual biological significance of the male’s overly developed mandibles.  Perhaps some knowledgeable expert will eventually write in with more details.

We are especially curious why the actual mating photos are blurrier than the others.  Was the activity especially frenzied with lots of wing flapping, or were you just a bit nervous behind the camera?  Any mating details would be greatly appreciated.

Daniel – the overall blurriness of those images was due to the fluttering of both the subjects in front of and behind the lens!  The dobsonflies were much more active during their “session,” and I also admit that I was excited due to your challenge in 2011 for dobsonfly mating pics relating to the male’s mandibles.  I’ve been an avid fan of WTB for quite some time – at least since 2002 when I successfully identified an American Pelecinid on there – so I remembered the “challenge” from back then.  I do apologize for the overall blur factor on those important pics, but hopefully you can make use of them and maybe clear them up a bit.  It was a fascinating evening and I’m glad that I can help the cause!  If I can help in any other way, just let me know. Many Thanks, Tim W. Wow Tim, You must have been one of our original ten readers.  We are happy you have stayed with us through the years.  Your photos are an excellent documentation, but there are still so many questions unanswered.  We can’t help but wonder:  Why was he poking under her wings with his mandibles?  Was that a required mating technique?  Why did she arrive at the light after him?  Was she attracted to his pheromones?  Is this a reversal of what is typical in most other insects’ mating rituals?  Were they both just attracted to the light?  Perhaps we will eventually learn the answers to some of these questions.                

Letter 4 – Dobsonfly from Costa Rica

 

Subject: White winged with pincers in CR Location: Costa Rica June 2, 2014 8:27 pm Found this guy in the Arenal rainforest area of Costa Rica on the side of a stucco building at about 8 am. It was approximately 3 inches total length. It would not move, even when I blew on it. Signature: Vmead

Dear Vmead, We believe we have identified your Dobsonfly as a Chloronia species thanks to an image on The Smaller Majority by Piotr Naskrecki.  You may also see a member of the genus on PBase, though both of the images we are linking to are considerably more yellow than your individual.

Letter 5 – Dobsonfly from Costa Rica

 

Subject: Giant Flying Whatsahoosit! Location: Atenas, Costa Rica June 11, 2014 7:48 am Hey There! I am in Costa Rica and when looking out the window one evening I discovered a very winged flying insect. It looks kind of like an ant or termite but doesn’t seem to have that type of mandible. It was roughly 3.5 inches long and just sat on the window screen next to an outdoor light all night. This is the rainy season and I am in Atenas, Costa Rica. I named it Steve and am sorry to say it has not returned on subsequent evenings. I mourn the loss of the bond we shared! ::sniff:: Let me know if you have any thoughts! Signature: -Jason

Dear Jason, We imagine this male Dobsonfly gave you quite a start when you first saw it from the other side of the screen.  While North American Dobsonflies are very impressive, the individuals from Costa Rica are even more impressive.  Male Dobsonflies are perfectly harmless, however, female Dobsonflies with their smaller and more practical mandibles, have been known to draw blood after biting.  Since Dobsonflies do not have venom, the females are also harmless, though a bite would cause some discomfort.

Thanks very much Daniel!  I see you have quite a bit of material on these creatures on your site. Fun reading! -Jason

Letter 6 – Dobsonfly from Canada

 

Subject:  Biggest bug I’ve ever seen Geographic location of the bug:  Laval, Quebec, Canada and Harrington, Quebec, Canada Date: 07/16/2018 Time: 08:01 PM EDT Your letter to the bugman:  Hi, here is a dead bug I saw today. It was near the Montmorency subway station in Laval. I’ve seen one just like it a couple of weeks ago near a lake in Harrington, Quebec, that one was alive but barely. They are about 3.5″ long including the wings. The kids think it’s a dead alien larvae… I’ve never seen bugs so big up here in Quebec, are they an invading species from the south, due to the warmer weather? Thank you very much for your great work. How you want your letter signed:  Yves

Dear Yves, This male Dobsonfly is a native species in your area, as well as in much of eastern North America.  Arguably, one of the most frighting looking insects, the male Dobsonfly is actually quite harmless.  His impressive mandibles are not capable of biting humans.  Living male Dobsonflies are even more impressive than dead individuals.