December 11, 2018
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Tiny, stingless wasp species discovered in Maine oaks

A tiny species of wasp the size of a grain of rice has been discovered in Harpswell oak trees.

Hillary Morin Peterson of Brunswick, who is now in graduate school, found the new species while working on her undergraduate honors thesis for the University of Maine in collaboration with the Maine Forest Service. She named the wasp Ormocerus dirigoius after Maine’s state motto, “Dirigo,” Latin for “I direct.”

The tiny insect is iridescent green and doesn’t sting, according to Peterson.

“I ended up catching a bunch of these cool little things I’d never seen before,” Peterson said.

“It’s not like I was in the field and was like, ‘Oh, look, this is a new species.’ It’s a longer process than that,” she explained. “What’s kind of an interesting point is you don’t have to go far to find new species. There are probably thousands and thousands of ‘new species’ in Maine.”

Born and raised in Maine, Peterson discovered her wasp while collecting samples for her thesis on the relationship between predatory and parasitoid wasps and the invasive winter moth. Her discovery was officially announced this week.

The wasps belonging to the previously undiscovered species, as it turns out, had nothing to do with the winter moth but were “swept up as bycatch,” Peterson said. She collected four specimens of the species from “beatings” of oak trees.

“It’s one of my favorite methods of collecting insects,” Peterson said, “Basically, what you do is take this thing called a beat sheet. It’s a big square sheer of a canvas with a wooden frame you can hold. Then you take something like a broom pole or big stick and you pick a branch, hold the sheer underneath it and hit the branch so the insects sitting on the branch fall down onto the sheet.”

The insects are then collected in vials for identification.

Identifying insects down to the species level of taxonomy requires a high degree of expertise and plenty of legwork.

To learn more about identifying wasps, which belong to a large order of insects called Hymenoptera, Peterson attended the Hymenoptera Blitz at Acadia National Park in 2015 with financial support from the Maine Entomological Society. There she met Dr. Robert Kula, who worked with her to secure an internship at his lab that fall at the Smithsonian Institution’s National Museum of Natural History in Washington, D.C.

“It was so cool,” Peterson said. “When I was a kid, I went to the Smithsonian. I loved insects and nature, and I have a picture of myself at the Smithsonian holding a cockroach. It was exciting to go and be a part of it, learning about that whole world.”

At the Smithsonian, Peterson collaborated with Dr. Michael Gates to identify her wasp.

“I was literally counting the number of hairs on the wings,” Peterson said.

Little is known about the biology of Ormocerus dirigoius, but the species may be associated with “galls,” which is abnormal plant growth usually found on foliage or twigs, on red oak trees. Details about the new species are in a recently published paper, “A New Species of Ormocerus Walker (Hymenoptera: Pteromalidae) from North America and a Range Expansion for Ormocerus latus Walker,” available through the Entomological Society of Washington.

Peterson is now a PhD student in the Department of Entomology at Penn State University. There she’s working to understand how parasitoid and predatory wasps interact with the brown marmorated stink bug, a pest that damages fruit, vegetables and nuts. Indigenous to Asia, this species of stink bug was accidentally imported to North America in the 1990s and has since spread throughout most of the country, including Maine.

“We also have native stink bugs, and we have wasps that are parasitoids that lay their eggs inside the stink bug eggs and are a natural enemy for the stink bug,” Peterson said. “I’m trying to figure out if any of those wasps are switching over” to the brown marmorated stink bug.


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