Beetle Hunter
Cerceris fumipennis
How to find the wasp that hunts emerald ash borer
Female Cerceris with Emerald Ash Borer
Cerceris is a solitary ground-nesting wasp. The female stocks her nest with buprestid beetles, including emerald ash borer (EAB) when present.
Observing colonies of these native wasps is currently the most promising way to monitor for EAB. The Maine Forest Service is looking for colonies of these wasps throughout the state, and would like your help.
Identifying Markings
- ½ - ¾ inch long
- dark smoky brown wings
- one cream/yellow band on second segment of abdomen (near “waist”)
- three large cream’/yellow spots on face
Markings of Female Cerceris fumipennis
(photos by P. Careless)
Cerceris can be found only in July and August
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What are Promising Nest Sites?
- hard packed sandy soil
- areas of human disturbance where the disturbance has been present for more than three years.
(school playing fields, baseball diamonds, trail and road edges, informal parking lots, fire-pits, camp-sites, etc.)
- full sunshine
- sparse vegetation (about 50% hard-packed soil and 50% short vegetation)
- near a wooded area (about 200 yards or less)
Typical Cerceris Colony Sites
(photos by P. Careless)
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How to Identify Nests
- round holes the diameter of a pencil
- holes go straight down (not angled into the ground)
- surrounded by a circle of excavated soil (not all to one side like a dog would dig)
- often tucked beside or under a clump of grass
- from 3-300 nests in a colony
Tip: Until you become familiar with Cerceris nests, carry a small piece of plastic or cardboard with a standard "hole punch" hole in it. This is about the size of a nest opening.
Cerceris Nests
(photos by P. Careless)
(Remember, if you want to monitor these colonies for EAB, they should be within 400 yards of ash trees.)
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Verify Nests Belong to Cerceris
- Look down the hole to see if she is looking back out at you (females often guard their nests just inside the hole). Remember, they don’t sting. Distinctive face markings should be easily visible.
- Place a clear plastic cup, punctured with breathing holes over the nest, and watch it. Weight the cup with a rock so it doesn’t blow away. You may see a wasp buzzing inside, trying to get out, or a returning female with prey, trying to get in.
- Capture her and look at her markings, then let her go. Tip over the cup and let her past.
Cups over Nests, and
Female Returning with Prey
(photos by P. Careless)
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What is Emerald Ash Borer?
- small metallic green beetle (1/2” long, 1/8” wide)
- an exotic beetle from Asia
- larva tunnels under the bark
- attacks and kills all species of ash
- first found in Michigan in 2002
- spreading VERY rapidly (primarily in firewood)
- so far, no reliable method of monitoring for it
Emerald Ash Borer
If you suspect you have found a Cerceris colony or would like more information, please contact:
Colleen Teerling: colleen.teerling@maine.gov
phone: (207) 287-3096
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