Hellgrammites: even their name sounds scary.
But as frightening as they may appear, they are among the more innocuous insect larvae you are likely to see in Maine.
Found under rocks in rivers or streams, hellgrammites are the larval stage of dobsonflies, which appear equally ferocious.
“It’s a really nasty looking critter,” said Jim Dill, pest management specialist with University of Maine Cooperative Extension. “The male is a really strange looking critter with two long mandibles out in front that can be an inch long [and] in the insect state the body can be 2 1/2 inches long with inch-long mandibles.”
Looks aside, dobsonfly larvae are probably best known as one of the best baits for bass fishing in Maine. Additionally, they only live in clean, pollution-free river water, making them a great indicator species of the water’s quality.
Dobsonfly larvae play an important role in measuring water quality in Maine, according to Jeanne DiFranco, aquatic biologist and manager of the Maine Department of Environmental Protection’s biological monitoring program, due in large part to its predatory nature and how long it remains in the larval stage — up to three years.
“Being longer lived means they are in the water for a longer period of time,” DiFranco said. “That means they can integrate the effects of any pollution sources over that period of time.”
That, and the fact that a hellgrammite is eating other things that live in the same water, would allow any pollutants to accumulate in its own body over time.
“If the larva is there for three years and still thriving, that’s a good thing,” DiFranco said. “The water has to be of good quality over that period of time.”
Adult dobsonflies do not feed at all, according to Dill. But the hellgrammites catch and eat small fish, other insect larvae and pretty much anything else that wanders by that they can catch with their sharp mandibles.
“They are a top predator in the bug world,” DiFranco said. “They are built for hunting.”
Despite those vicious-looking pincer attachments, hellgrammites pose little threat to humans. They will try to bite if they are harassed and those pincers can pierce the skin, but the bites are not harmful.
“Those mandibles are mostly for show and, on the males, for tussling with other males for mating,” Dill said. “I have handled them before and have never been bitten, but I am careful because even if I get bitten by accident, it could be painful.”
DiFranco said she’s never been bitten, but did have one latch on to her finger one time and said it was with impressive force.
Hellgrammites used to be commonly sold in bait shops around Maine, but Dill said that stopped when sales began depleting the natural populations of the larvae. Today, dedicated bass fishermen spend time turning over rocks to collect their own.
“These critters are part of our ecosystem,” Dill said. “They are an important part of the food chain and a pretty good meal for fish and other critters.”