Megaloptera (dobsonflies and fishflies)

Order Megaloptera Description

This order of insects includes the alderflies, fishflies, and dobsonflies.  Although every species of Megaloptera is aquatic at some stage in its life cycle, unlike Odonata (dragonflies) and Ephemeroptera (mayflies), Megaloptera is usually only aquatic in the larval life stage.  Larvae are found in a variety of lentic (slow moving) and lotic (fast moving) water systems, while adults are found in wood or beneath stones near the water’s edge.  Adults are rarely seen due to their short life span, lasting on average only 8 days, and because they are mainly active at night.  Megaloptera, especially adults in Corydalidae, are known for their large size.


Megaloptera Families:
Click on each to display information below .


CorydalidaeFamily Corydalidae

Dobsonflies, Fishflies, Hellgrammites

Corydalids are commonly referred to as alderflies, dobsonflies and fishflies, the larvae of this family are often called hellgrammites.  As larvae, these insects are found in moderate to fast moving current in streams and rivers, except for one genus that inhabits still water, and lives under rocks and debris as adults.  Larvae have an average body length between 25 and 90 mm, while adults may be 40 to 75 mm long.  Corydalid adults are most easily recognized by very long and conspicuous mandibles, or mouth parts. Adults have gray, black, or brown bodies with opaque wings.  In some species the wings are almost black with white markings, but most Corydalids have opaque wings with a brown mottled pattern.  

An adult female may lay clusters of as many as 2,000 to 3,000 eggs at a time.  The eggs, which are laid on vegetation overhanging a stream, resemble bird droppings.  After the larvae hatch, they will fall into, or crawl to the water.  Corydalids exhibit a varied response to water quality.  The larvae are predators that leave their hiding places at night to hunt for prey.  Corydalid larvae have small hooks on their abdomens that allow them to attach to rocks and substrate to prevent being swept away by the current.  Corydalid larvae are not very good swimmers, so these hooks are also used to help the larvae crawl along the substrate.  Caution should be used when handling Corydalid larvae because some species may inflict a severe bite when touched.  Some species are extremely sensitive to pollution and dissolved oxygen levels, while others are more tolerant.  In general, species that inhabit slow moving water systems are more tolerant to pollution than species found in lotic habitats. 


Megaloptera Life History
Larvae and Pupae
The larval stage is the only stage in the Megalopteran life cycle that is aquatic. As soon as the larvae hatch from the egg they either drop or crawl to the nearest body of water.   The larval stage may last as long as 2 to 3 years.  The egg, pupae, and adult stages are terrestrial.  When a larva is ready to pupate, it will crawl out of the water and burrow into a 1 to 10 cm deep hole dug into the shoreline.  This burrow acts to protect the pupae while it is developing into an adult.  Pupae will develop within this burrow until they are ready to emerge as an adult.

Larvae have chewing mouth parts and lateral filaments on the abdominal segments.  They possess either a single caudal filament, or a pair of anal prolegs.  In addition, there are two tarsal claws at the end of each leg.

Pupae will emerge as adults after development for 1 to 4 weeks in the pupal stage.   Emergence occurs in late spring to early summer.  Alderflies are active during the warm daylight hours, while dobsonflies and fishflies are noctural.  Once pupae have developed into adults, they tend to stay near their larval and pupal habitat for the remainder of their lives.  The adult stage, as well the egg and pupae stage, is terrestrial.  The adults live for an average of 8 days.  Adults have large mandibles (mouthparts) and wings; the wingspan in some species may reach up to 180 mm.  Adult Megaloptera lay eggs on rock surfaces or vegetation that often overhangs a body of water.

Feeding Habits
Larvae are predaceous and feed on small insect larvae, mollusks, or annelids.  The adults do not possess mouthparts, and consequently, they do not eat. 

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