Seminole Crop E News

Agricultural News for Farmers and Agribusiness in SW Georgia

Question of the Week – Hellgrammite

Posted by romeethredge on October 16, 2015

Last week I had a photo of an amazing creature often found under rocks in our creeks. It’s the hellgrammite or the adult would be the Dobson fly.

The hellgrammite aka gatorflea, is the larval stage of this insect and it lives an aquatic life. FullSizeRender

Hatching from an egg case placed on a rock ledge or branch that overhangs the river, young hellgrammites fall into the water that will become their home for one to three years. On the same day we saw the hellgrammite we saw the egg masses on leaves over Notchaway creek. I’ve often seen them over Spring creek as well. They are quite large. Here’s some we saw on a leaf overhanging Notchaway creek. 

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Growing to a length of two to three inches long the hellgrammite resembles a centipede with a powerful set of pinching mouthparts, but it possesses only six legs. The remainder of its body is lined with six to eight pairs of thick filaments that act as gills for underwater breathing. Hellgrammites live underneath rocks, submerged logs, and debris in the swift river currents, hunting and feeding on other macro-invertebrates.

Hellgrammites are a useful in identifying the quality of their river habitats because they can survive only in relatively clean and well oxygenated water. Fisherfolk also consider them to be one of the prime live baits for fishing. Be careful, hellgrammites resist capture by their ability to “pinch the blood” out of human fingers that try to pull them from the water.

After years of aquatic life, in late spring, hellgrammites, often synchronized in great numbers, emerge from the water to burrow into the mud of the riverbank or find shelter under a rock or a log, in order to begin a pupal stage lasting from several weeks to a month. Some folks report that thunderstorms trigger emergence of the hellgrammites – a phenomenon known as “hellgrammite crawling”.

From this stage the creature will emerge from a complete metamorphosis into a winged Dobson fly.

Male and female eastern dobsonflies, Corydalus cornutus (Linnaeus), showing differences in mandibles and antennae.

Dobson flies have short but intense winged lives. Males live about three days and females ten days. It is rare to see them.  In search for a mate, the Dobson fly does not eat, but may fly many miles over or away from the water in search of a mate. An adult Dobson fly is an impressive sight; three to four inches long with even longer wings, they definitely are a sight to see. The males especially stand out with their exceptionally long, curved pinchers. Don’t worry about a bite though, they are harmless and used only for mating.

With the deposit of their white circular egg masses on objects overhanging the river the double life of this amazing creature ends.

Much of the above information from National Park Service publications.

 

This week’s question is about an insect that I have photos of here. What is it and what is it good for?

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