In the dark, it’s understandable that Dobsonian flies frighten residents – the flying insects can grow up to 5 inches long and have crescent-shaped mandibles. Although the females’ jaws are smaller, they are strong and able to draw blood.
But there is a relatively simple solution – don’t put a finger near your mouth.
Reports have surfaced across the region of Dobson’s flies, described as the “most terrifying” insect in the Commonwealth.
But they’re really not a threat to humans – in fact, their presence can illustrate a healthy ecosystem – and a simple bulb change could keep these nocturnal bugs off porches at night.
To learn more about these scary-looking insects, The Morning Call spoke to Marten Edwards, a professor of biology at Muhlenberg College.
Where do you live?
Immature Dobson flies, known as Hellgrammites, spend their time in clean, cold water, where they are “wild predators,” Edwards said. They like to live in rocky areas by streams and feed on minnows for one to three years, most of their life.
As adults, they live on land and grow wings for the last, shortest part of their lives. Adult males only survive three days and the females live about a week.
They are drawn to the light, which could be one reason they show up on porches.
“If there is an increase in the number of people seeing them that I have no evidence for, but if so, it may be because people are buying these porch lights that are incredibly bright and maybe brighter than necessary, but that’s what they do attracts, ”he said. “So your porch light will confuse it and it will fly there.”
Since they are nocturnal, if residents find any during the day, they will most likely be inactive, Edwards said.
While he’s seen them on the Mühlenberg campus, residents are more likely to see them near streams than in a town, he said.
“You are really lucky if you can see (her),” he said. “Maybe if you live near a creek and have a super bright torch light, you can see some of them. But the average person in a built-up area will really be happy to see one of them. “
What is its purpose?
Their purpose is simply to continue their life cycle. As adults, they are driven to have families, Edwards said.
“You have a small window of opportunity,” he said. “This is the time they come out of the water looking for a mate.”
Are you aggressive?
The female’s mandibles are able to draw blood, but that doesn’t mean they’ll go out of their way to do so, Edwards said.
“If you handle that when you pick one up and stick your finger in it, it could probably pinch you,” he said. “It won’t haunt you; it’s not aggressive. I would put them in the completely harmless category. “
Why do they look so scary?
The mandibles are for defense, he said. But also the males of the species can show off to the ladies.
“These large mandibles, like the giant deer antlers, can be used as a kind of spectacle,” said Edwards. “So, it’s a reproductive structure for him, perhaps in terms of women choosing him because he has great looking mandibles.”
Males also use their jaws to hold the females’ wings while mating, he added.
What can you say about our environment?
Finding Dobsonian flies is actually a sign of a healthy ecosystem, Edwards explained, illustrating how healthy a creek was for months or even years.
“It’s much better than sticking a little probe in and seeing what it is in this particular case, or doing a chemical sample at that particular point in time,” he said. “When you see what kind of insects are there, you can see how healthy this environment was over a much longer period of time.”
How should people behave when they see them?
Since they are not aggressive, residents only need to stay away from them if they fear they will be trapped or bitten.
But when they’re around, don’t bump into them.
“Don’t put your finger in there,” said Edwards. “In short, admire them – leave them alone.”
What else should residents know about them?
When several show up on a porch, drawn to the light there, Edwards said it might be time to think about how much light the porch really needs.
“I know a lot of people are now buying these lights that would be good for lighting up an entire sports arena, maybe a little more than you need from your porch,” he said. “And this incredible amount of light that some of these lights produce is particularly harmful to many insects, especially the fireflies, which need darkness to go through their life cycle.”
Changing a porch lighting from a bright white lightbulb to one with warmer tones, amber colors, should do the job, he said.
“The light will be much more comfortable for people,” he said. “But it won’t be as visible to most insect species that would be attracted to light either.”
