It's big, it's scary, and it's coming soon to a streetlight near you!
The Dobsonfly is the adult stage of a large member of the Order Megaloptera. They have a fearsome appearance, being up to 5 inches in length from the tip of their wings to the tip of their mandibles, possess 2 pairs of wings, 1 pair of segmented antennae, and the aforementioned mandibles. The males especially are a horror to behold, their long pincer-like mandibles over an inch in length. These seeming tools of destruction are too weak to inflict damage to humans and are instead used to impress female Dobsonflies, then are used to hold the female during mating. The jaws of the females are far less impressive, though much more dangerous. They are capable of inflicting a painful pinch, drawing blood from unprotected skin.
The adults are nocturnal, seldom being seen during daylight hours. They are however attracted to bright lights during the night. The light draws them and they can provide a bit of a scare with their threatening appearance.
The form or phase of Dobsonfly which is perhaps more familiar is their larval stage, commonly known as hellgramites. These insects are aquatic, and head for water as soon as they hatch. Once there they are predators, happily snacking on the nymphs of other aquatic insects as well as small minnows, tadpoles, and whatever protein their environment provides, including their own brethren. They hide under stones or submerged vegetation and logs which provide cover as well as helping preserve moisture during dry periods. These larvae are also prey to others, especially fish. Anglers use hellgrammites for bait, secure in the knowledge that Mr. Bass finds them irresistible.
The larvae grow for 1-3 years, undergoing up to 11 instars before arriving at the pupal stage. They possess 3 pairs of true legs and several pairs of filaments, or false appendages. Their bodies are segmented, containing 10 abdomenal segments and 5 segments to their tarsi. The eyes are large. The mouth parts are strong, as one would expect in a carnivore. They feast on the soft inner parts of prey.
The Dobsonfly emerges from water to pupate. Sources disagree concerning the duration of the pupal stage. There are reports that the mature larvae emerge at the same time to pupate, supposedly an event triggered by thunderstorms. This theory possesses some logic as the insects require a moist environment, which would be fostered by thunderstorms.
There is coordination of adult emergence which helps provide mating success. The adults emerge to quickly mate, lay eggs to continue the species, then die. The adult phase lasts only a few days and they either eat rarely or not at all. Females lay their eggs, (up to 1,000 of them), often on a leaf or rock suspended over water, which the larvae drop into upon hatching.
The wings of Dobsonflies are folded lengthwise along the body when not in flight. Their cousins the dragonflies cannot fold their wings, but make up for that peculiarity by being masterful fliers.
The Dobsonfly can be found in Asia and North America.
Superorder: Endopterygota or Neuropterida