Transcript:

Today on Animal Fact Files we’re talking about dobsonflies. The adult form of these animals is known as the dobsonfly, however, the larval form is known as the hellgrammite. So, dobsonflies and hellgrammites are the same animal, the names just apply to different life stages. Currently there are more than 100 recognized species, but as we always say this is subject to change with new research and information. Dobsonflies are most commonly found in the Americas and Asia, though they do also live in Africa. There is also a species commonly called a dobsonfly that lives in New Zealand, however, this species belongs to a different subfamily than the subfamily we’re discussing today.

Dobsonflies are big! When not counting butterflies and moths, dobsonflies can be some of the largest insects living in the areas they inhabit. Adult dobsonflies can have wingspans of more than five inches (12.7 centimeters) and the larvae can easily reach three and a half (90 millimeters) in length! Of course, they don’t start out this way.

Dobsonflies begin life in eggs. Female dobsonflies may lay thousands of eggs either on the ground, on leaves or anywhere else that’s adjacent to water. Sometimes she’ll even cover the eggs with a chalky, white substance that makes them look like bird droppings! The eggs take about a week to hatch and the newly born larvae will make their way to the water. Though adults, pupae, and eggs are terrestrial, dobsonflies spend their larval stages living in water, so water needs to be present in their habitats. The larvae will stay in water as they develop. In colder areas it can take years for the hellgrammites to reach full size and move on to the next stage in their lifecycle, but in warmer areas they develop faster. The larvae will molt at least ten times before they’re ready to pupate.

When hellgrammites begin the process of turning into pupae, they will pull themselves out of the water and find areas in which to dig. Hellgrammites don’t produce cocoons, but they will carve out hollows in the ground that act like cocoon chambers. After about two weeks, adult dobsonflies will emerge from the pupal chambers and immediately seek out a mate. This is because dobsonfly adults don’t usually live longer than a week. The adults’ lives are so short, in fact, that most of them don’t even eat.

Dobsonflies almost exclusively eat during their larval stage. In areas where they occur, hellgrammites may be the top invertebrate predators. These insects are carnivorous and will take the larvae of other arthropods as well as worms and molluscs. They have a strong bite. Some adult male dobsonflies with their inch (2.54 centimeters) long mandibles may look more fearsome than their progeny. However, male dobsonflies are basically harmless to humans. It’s the larvae and the females that people have to watch out for as these have a bite strong enough to draw blood.

Hellgrammites prefer clean, pollution-free water systems, so they can be a good indicator of a habitat’s water quality. They spend a lot of their time hiding under rocks and sunken debris which tends to keep them safe from the watchful eyes of predators, though they are likely opportunistically taken by fish and crayfish. Adult dobsonflies avoid predators by limiting their activity to dusk and night. They may still fall victim to birds and bats, though. Some species of dobsonflies are also hosts to parasitic wasps - specifically their eggs may be taken over by wasp larvae, which is a really gruesome way to go.

For more facts on dobsonflies, check out the links in the description. Thank you to blairemou5 for today’s request. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files!