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

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.

Dobsonfly Structural Adaptations

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

1. How do dobsonflies protect themselves?

In the larval stage of its life cycle, the dobsonfly is an ambush predator that hunts other insect species in the water using pincer-like mandibles. 
Adult dobsonflies use these same mandibles for self-defense and to fight off rivals during the breeding season. In males, the mandibles grow significantly larger upon maturity.

2. How many eyes does a dobsonfly have?

Dobsonflies shares several similarities with dragonflies. This applies to their eyes too. Just like dragonflies, dobsonflies have three simple eyes. They are not able to see a whole lot with them, but it is enough for them to see the light and shadows.

3. How many legs does a dobsonfly have?

Like most members of the insect world, dobsonflies have three pairs of legs. Hellgrammites appear to have many pairs of legs and closely resemble centipedes in this respect. 
However, they have the same number of legs as adults. The remaining leg-like appendages aren’t real legs – they have tracheal gill tufts at their ends.

4. What happens if a dobsonfly bites you?

There’s no need to panic about a dobsonfly bite, as they don’t cause any diseases. 
Although the females can inflict a painful bite, the pain doesn’t last long. As for the males, their mandibles are too long to bite properly. Their bites aren’t painful at all.

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.

Authors

    by
  • 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.

14 thoughts on “Dobsonfly Structural Adaptations: 9 Tips To Surviving in The Water”

  1. I was preparing the post of a male dobsonlfy and then, WOW! Nice hardcore scenes, I have to link it: http://www.insetologia.com.br/2013/08/coridalo-macho-no-rio-de-janeiro.html
    One thing I have to ask you. Do you have a report about the female dobsonfly bite? It’s said to be a very effective bite, but Barbara (the one of the grasshopper http://www.whatsthatbug.com/2013/02/01/unknown-grasshopper-from-brazil/) said it was a “gently bite”.
    http://www.insetologia.com.br/2013/02/megaloptero-em-minas-gerais.html

    Reply
    • Hi Cesar,
      Male Dobsonflies would have a very difficult time biting a human. Female Dobsonflies and larval Hellgrammites have more utilitarian jaws that might produce a painful, though not dangerous bite.

      Reply
  2. I was preparing the post of a male dobsonlfy and then, WOW! Nice hardcore scenes, I have to link it: http://www.insetologia.com.br/2013/08/coridalo-macho-no-rio-de-janeiro.html
    One thing I have to ask you. Do you have a report about the female dobsonfly bite? It’s said to be a very effective bite, but Barbara (the one of the grasshopper http://www.whatsthatbug.com/2013/02/01/unknown-grasshopper-from-brazil/) said it was a “gently bite”.
    http://www.insetologia.com.br/2013/02/megaloptero-em-minas-gerais.html

    Reply
  3. Cesar – glad you like the pics! I have handled the females numerous times and have never been nipped. I’m not sure I would pick up the Hellgrammite, though. They look like the kind of thing that is “best to not test!”

    Reply
  4. Colleagues:

    The females of a large species of Corydalidae, common in Serra do Cipó mountains, central Minas Gerais States, Brazil, are very aggressive, and may bite quite strongly, and sometimes pick up some blood (as well as some Isoptera and Atta soldiers), in persons with thin skin (white people); the males are absolutelly innofensive, with weak bite.
    They are attracted to light in some nights.

    Celso Lago-Paiva
    Instituto PróEndêmicas
    http://br.groups.yahoo.com/group/proendemicas/

    Reply
    • Dear Celso Lago-Paiva,
      Thank you for qualifying the biting capabilities of female Dobsonflies with the information that only “thin skinned” individuals need to be concerned.

      Reply
  5. Colleagues:

    The females of a large species of Corydalidae, common in Serra do Cipó mountains, central Minas Gerais States, Brazil, are very aggressive, and may bite quite strongly, and sometimes pick up some blood (as well as some Isoptera and Atta soldiers), in persons with thin skin (white people); the males are absolutelly innofensive, with weak bite.
    They are attracted to light in some nights.

    Celso Lago-Paiva
    Instituto PróEndêmicas
    http://br.groups.yahoo.com/group/proendemicas/

    Reply
    • Thanks for bringing that to our attention Curious Girl. We generally correct inaccuracies in content in an inquiry. We are not able to locate any images of Dobsonflies in the genus Chloronia with scimitar-like mandibles online, so, there are either no images of males online, or in this genus, there is not as much sexual dimorphism.

      Reply
  6. I like your site, and this entry is in my backyard. We have been in CR for a year now and everyday brings a bug or animal we haven’t seen.

    Reply
  7. It looks like in courtship the males uses his long mandibles to stroke the female, and in photos 5 & 7 he has hooked one over one of her wings, maybe gently pulling? The mandible is the perfect size & shape to hook over her big wing, maybe that is one of its functions.

    Reply

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