Creature Feature Dobsonfly


An insect with looks that only its mother can love

Have you ever been outside at night under a street light and seen or been buzzed by something and you thought “WHAT IN THE WORLD IS THAT?!”. That insect as big as a Pterodactyl (okay a mini one) might be a Dobsonfly. Is it 4.5 to 5 inches long, with HUGE 1” mandibles, four veined wings, and wavy antennae? Okay, that is Mr. Dobsonfly. How can you tell? Mrs. Dobsonfly is a bit larger than the Mr., but her mandibles are shorter and stouter. The male has weak mandibles and can’t bite you but she most certainly is able to give you a painful bite if not handled carefully (like nope). They will both try to intimate by raising their head and spreading their jaws (that would work for me), but neither will go out of their way to harm you. And even if you are “silly enough” to get bitten her bite is harmless. Dobsonflies don’t transmit any diseases and there aren’t any lasting effects (other than learning a lesson). PSA: as a defense of last resort the threatened Dobsonfly can emit an irritating, foul-smelling defensive anal spray. Well, that is…interesting.

This fascinating prehistoric looking insect is one that has a complete metamorphosis referred to as ELPA. It begins as an Egg, hatches into Larvae, transforms into a Pupa, and finally emerges as an Adult. The egg is attached to structures, rocks, or trees overhanging a stream or river and hatches within 1 to 2 weeks. The newly hatched larvae (called Hellgrammites, more on them in a later creature feature) drop into the water and position themselves in a suitable feeding site under rocks. Hellgrammites, said to be great bait for small mouth bass and river trout, will feed and grow up to 3 inches in length taking up to 3 (more or less) years. When mature, Hellgrammites will migrate out of the water, sometimes as far as 50 feet, to dig a cell in wet soil, moss, or decaying vegetation to pupate. The pupa will stay in the cell for 7 to 14 days then the adult will dig its way out.

The adult stage puts the insect on a fast track. The male will live about 3-5 days while the female up to two weeks during which time it is thought that they don’t feed. (Explains why the female might bite, she is hangry!). Their mission of course is to continue the next generation. They spend most daylight hours in the canopy of trees or in thick vegetation near streams or rivers. But they are most active at night and are strongly attracted to light which makes them at risk during this time as food for bats, large invertebrates while during the day birds, and fish. Though they have large wings spanning up to 5 inches, they are not great fliers but can be found quite a distance from rivers or streams.

So, if you see a Dobsonfly in town, or get buzzed under a street light, YOU ARE SO LUCKY!

P.S. Dobsonflies while scary looking, are harmless to humans, animals, property, and crops. No control treatments are necessary. So, enjoy, take a picture, then please leave them alone.

Written by Diana Flynn