#dobsonflies

Do you get me? (Dobsonflies)

Fast Fauna Facts #22 - Eastern Dobsonfly (Corydalus cornutus)

Family: Dobsonfly Family (Corydalidae)

IUCN Conservation Status: Unassessed

Like most dobsonfly species male Eastern Dobsonflies like the individual pictured above have enormous mandibles used to impress females, wrestle with rival males and grip partners during mating, but despite their intimidating appearance these mandibles are fairly weak and are unlikely to cause significant injury to humans. Ironically, the much shorter mandibles of females are significantly more powerful, with an adult female Eastern Dobsonfly potentially breaking skin if provoked. While both male and female Eastern Dobsonflies possess impressive jaws neither actually feed as adults, instead spending the entirety of their short lives gathered around shallow slow-moving streams attempting to locate and impress mates. After mating female Eastern Dobsonflies lay eggs on rocks or plants hanging over water, and the newly-hatched aquatic larvae, known as hellgrammites, are born with extremely powerful jaws used to feed on smaller insects as they grow.

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Image Source: Here

Cool facts about the majestic dobsonfly!!

- If you’ve heard the term “Hellgrammite” before, that’s actually referring to larval dobsonflies.

- they exhibit sexual dimorphism in their mandibles. Male dobsonflies have long mandibles used for attracting a mate, while female dobsonflies have shorter mandibles that they use for biting.

- they can grow to be quite large, ranging from 3-4 inches (~7-10 cm) in length. Their wingspan ranges from ~7-8 inches (~18-21 cm)

- they can be yellow. This is very important.

Nevromus austroindicus Liu & Viraktamath, 2012. From Mudigere, India.

- Acanthacorydalis fruhstorferi, a species of dobsonfly, is the largest aquatic insect in the world.

Elements of Zoölogy: A Text-book. Written by Sanborn Tenney. 1875.

Darling Eastern Dobsonflies

requested by @skyroller

Eastern dobsonflies (Corydalus cornutus) is a distinct species of insect commonly found in the eastern rivers of North America. They go through several stages over the course of their lives, which in total can last as long as three years. They begin as eggs, laid close to water in clusters of up to 1,000. These clusters often resemble bird droppings as a form of camouflage. About a week or two after being laid, the eggs hatch into the form they spend most of their lives in-- the larvae known as hellgrammites.

Hellgrammites are aquatic, spending most of their time under river rocks. Over the course of 1-3 years, these larvae can molt up to 12 times. In late spring or early summer they finally emerge from the water, burrow into the soft soil of the river’s edge, and pupate. In colder regions C. cornutus remains dormant throughout the winter, but in warmer regions adults emerge after only 1-2 weeks. Male adults use their powerful jaws to fight each other for access to females, and after successfully mating both males and females die.

Larval C. cornutus have dark brown or black segmented bodies with 3 pairs of legs. Protruding from each segment is a filament with a gill tuft at the base, which they use to breathe under water. In addition to these, hellgrammites have a set of external respiratory openings called spiracles, with which they can also breathe on land. Adult dobsonflies look significantly different. The abdomen, while still segmented, is lightened to a tan and becomes more elongated; in total they can be up to 14cm long. The filaments are gone, replaced with 2 sets of large wings, which reach spans of 13cm. Adults also have a pair of antennae, which they can use to locate the chemical signals emitted by potential mates. Male C. cornutus sport a large, curved set of mandibles, which make up almost half their body length.

Because adult dobsonflies die soon after mating, they don’t eat. Hellgrammites, however, consume a wide range of smaller insects and larvae, mollusks, and crustaceans, making them important low-level predators in their native rivers. Both larvae and adults host a large number of predators including fish, crayfish, birds, and bats. Hellgrammites are also a popular choice of bait for fishermen. To protect themselves from predators, larvae and adults have mandibles that can deliver a powerful bite. They are also active primarily at night to avoid diurnal predators.

Conservation status: The eastern dobsonfly has not been evaluated by the IUCN. However, over collection for fishing may deplete populations, and larval dobsonflies are vulnerable to river pollution and deplition.

Photos

Jim Rathert

Isaac Szabo

Michael Raupp

adults: Didier Descouens, license, note that the male has the longer mandibles and the female the short ones; larva: Salsb, public domain, note that larvae are often much darker in color

Common name(s): dobsonflies, hellgrammites (larvae), "demon moth" by some of my parents' friends who wanted to know what they'd found in their garage

Scientific name: Subfamily Corydalinae

Can it hurt me?: It's unlikely, but possible. Oddly, even though the males have larger mandibles than the females, the females are the only ones even capable of biting. The extra long male mandibles are just a sex thing. They rarely bite and only do so when threatened, but when they do it can hurt quite a bit. It should be mentioned, though, that they are not venomous nor do they carry any diseases so the danger of the bite is just in the hard pinch it can give.

Can it hurt my plants?: No

Should I kill it?: Using the hellgrammites as bait will kill them, but there's no need to go around targeting them for extermination. You can pretty much leave the adults alone as well.