Brazos Bend State Park
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Gator Hatch

Pond Life of Brazos Bend State Park

Fishflies and Dobsonflies: Order Megaloptera

Family Corydalidae

Fishflies and Dobsonflies make up the family Corydalidae. Some authorities classify this family as belonging to the order Neuroptera while others put them along with alderflies in a separate order, Megalopera. They are large flying insects whose long bodies resemble that of a dragonfly, but whose wings are much larger in proportion to their bodies, and are very lacy and delicate looking.

Dobsonflies are distinguished by their large mouthparts. The male dobsonfly's mandibles look like a pair of ice tongs, while the female's mandibles look like the jaws of a vise. Fishflies mandibles are smaller. Their distinguishing feature is the pair of large feathery antennae on their heads. Dobsonflies are only found occasionally in the park. Fishflies are very common in the park, especially on summer nights.


Fishfly (Chauliodes) 1.5 inches long

Hellgrammite, probably fishfly, 1 inch long


Although dobsonflies and fishflies are flying insects, their larvae, called hellgrammites are aquatic. Hellgrammites resemble a long worm with spindly legs and many long thread-like growths on their abdomens. These threads act as gills, and help the larva to breath underwater.

The mandibles are large and powerful, with jagged teeth in them. Hellgrammites are active hunters. They catch smaller animals with their large jaws, and swallow them whole.

Some hellgrammites may grow to be over 3 inches long. They are often raised or collected and sold as bait to fishermen.


Hellgrammite showing powerful mandibles

Hellgrammite showing claws on proto-legs at the end of its abdomen.


Corydalidae larvae look very much like the larvae of the water scavenger beetle. One way to tell them apart is that hellgrammites have a pair of appendages called proto-legs on the last segment of their abdomen. Each of these proto-legs has a pair of claws on it.

Hellgrammites may live in the water for up to 3 years before becoming adults. They crawl out of the water, dig a small hole for protection and go into a pupal state for from 1 to 14 days. They then emerge as adult insects and fly away. Their adult stage is very short, only 8-14 days.

Corydalidae larvae are considered good indicators of water quality because they are sensitive to pollution.


Arachnids – Spiders and relatives

Dragonflies and Damselflies - Odenata


Updated: Aug 12, 2011