August — Dobsonfly

Remember when we wrote about antlions - those little critters that grab prey from the bottom of a sand pit? No? Well, anyway, the topic of this month, the dobsonfly, is a (somewhat distant) relative of the antlion. Like antlions, dobsonflies spend most of their life in the larval form and are very predaceous.

Dobsonfly larvae, however, are aquatic critters known as hellgrammites that can live 1 to 5 years in the larval stage. Hellgrammites have strong jaws and ambush prey from protected locations beneath stones in fast-moving streams and rivers. Prey animals include other insects as well as fish, frogs and salamanders. Although the larvae obtain dissolved oxygen from abdominal filaments, they also have spiracles, or small holes, which allow them to take in air directly and help them to survive dry periods.

When larvae mature, they crawl out of the water and pupate within a protective cocoon where they overwinter. They emerge as 4 to 6-inch, winged adults. The adults apparently do not eat, but mate and die within a week or so.

The nocturnal adults are seldom seen, but you won’t forget them if you do see one. They are attracted to lights and are generally found from late spring through mid-summer near bodies of water (we saw one in early August). After mating, females deposit their eggs on vegetation near the water. Upon hatching, larvae then crawl to or fall into the water.

Although the adult males have very long and dangerous-looking pinchers, the jaws are too weak to harm humans and are used for grasping females during mating. The females, on the other hand, retain their fierce larval jaws and can inflict a painful bite. Both males and females assume a menacing posture when threatened, as they raise their heads and spread their jaws. They can also emit a foul-smelling anal spray.

More on the dobsonfly: