Bug Fact: Dobsonflies spend most of their life in the larval stage, during which they are called hellgrammites, “grampus,” “go-devils,” or “crawlerbottoms”, and are familiar to anglers who like to use the large larvae as bait. Hellgrammites live under rocks at the bottoms of lakes, streams and rivers, and prey on other insect larvae with the short sharp pincers on their heads, with which they can also inflict painful bites on humans. The larvae reach to 2″ to 3″ in length, with gills all along the sides of their segmented bodies that allow them to extract oxygen from water.
After a few years of living and growing underwater, the larvae crawl out onto land and pupate. They stay under large rocks for 3 weeks before molte and emerge only to mate. Upon emerging, they live for only seven days.
Adults can generally be found from late spring into the middle of summer, preferring to remain near bodies of water, particularly the ones where they grew up. Once they emerge as adults they mate, deposit their eggs near the water (often on overhanging vegetation), then die. They are primarily nocturnal, and like most aquatic insects, are commonly attracted to bright lights.