Eastern Dobsonflies

     Occasionally someone will notice a two-inch-long, brown insect on an outdoor wall near a stream on a summer day.  It will have a pair of two-and-a-half-inch-long, clear wings stretching beyond the end of its abdomen, making it look like a miniature Dracula.  But, perhaps most frighteningly, it will have two tusk-like mandibles that are about half as long as the body, curved inward and crossing each other.  The insect is an adult male eastern dobsonfly, which is harmless to us.
      Adult dobsonflies are active at night, but rest during the day, perching on trees, walls and other objects.  They are more common than we know.  Most of them just are never seen by people because they are at rest during the day. 
     Female dobsonflies are similar in appearance to males, but have much shorter mandibles.  But females can bite!  And being one of the largest of insects in southeastern Pennsylvania, and elsewhere, both genders have up to five inch wing spans. 
     Dobsonflies seek mates at night near the stream they grew up in, early in summer for the most part.  It's thought they don't eat during that time of breeding.  Males flutter their wings and try to push their long mandibles under male dobsonfly opponents to flip them over.  Winners of those struggles get access to the girls. 
     After mating, female dobsonflies spawn up to 1,000 eggs in rounded masses on rocks near the waterways' edges where they lived as larvae.  They spawn at night, any night from May to September.  Each mass is covered by a chalky-white substance, to keep the eggs protected and moist.  After hatching, the larvae crawl to the water where they live from two to three years, or more.
     Dobsonfly larvae in the water are called hellgramites.  They live under stones on stream bottoms, eat aquatic insects and grow to be two to three inches long.  They are dark which allows them to blend into the stream bottoms and be invisible, wrinkly and worm-like.  But each one has a pair of hooked, anal prolegs for hanging onto stones so they don't get washed away in the current.  Those large, scary-looking larvae are often used as fish bait, especially for trout that readily consume hellgramites in moving streams.
     Hellgramites need good water to survive.  Therefore, they are indicators of water quality.  Their presence in a stream speaks of good quality water.  
     When mature, hellgramites crawl out of the water and make pupal cells of soil under stones, logs and other debris near the water.  Here they overwinter.  Adults emerge early the next summer ready to find mates, breed and spawn eggs.  And that is when some people find them on outdoor walls near the streams they grew up in.                         
     Adult dobsonflies are eaten by raccoons, bull frogs, certain kinds of birds and other predators.  It's good they spawn lots of eggs  to make up for losses.
     If the reader finds a dobsonfly, there is no need to be afraid of it.  Just leave it alone and it won't bother anybody.  In fact, they are quite interesting to experience.  And they and their larvae are parts of several food chains of who eats whom.