Bug FAQTherion circumflexum
Therion circumflexum · Order: Hymenoptera · Family: Ichneumonidae
Therion circumflexum adults are relatively large wasps about 14 to 25 mm long, with a black head and thorax, a yellow scutellum, orange abdomen, yellow-orange legs and orange-hyaline wings. Females have a short ovipositor spike and lay eggs inside caterpillars; the larvae feed on the host and later pupate in a thin web. Adults are on the wing from mid-June through September.
Source: Wikipedia
How to recognize it
The head and thorax are mainly black. The scutellum is yellow. The abdomen is mostly orange. Legs are yellow-orange. Wings are orange-hyaline. Females have a short spike on the abdomen.
Source: Wikipedia
Size
Body length ranges from about 14 to 25 mm (0.55 to 0.98 in).
Source: Wikipedia
Where it lives
Adults fly from mid-June to September.
Source: Wikipedia
What it eats
The wasp parasitizes several moth species, including small engrailed, privet hawk, pine hawk-moth, pebble prominent and various owlet moths. Females lay eggs inside caterpillars; the hatched larvae feed on the host.
Source: Wikipedia
Life cycle
Adults are active from mid-June to September. After feeding inside the caterpillar, larvae later pupate within a thin web.
Source: Wikipedia
When you see it
The flight period spans mid-June through September.
Source: Wikipedia
Where it comes from
It is widespread across much of the Palearctic region and also occurs in North America.
Source: Wikipedia
Where it is found in the US
Recorded in 21 of 51 states and DC. Most records: Maine, New York, Minnesota, Colorado, Washington, Ohio, Massachusetts, Michigan.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Months it is reported in the US
Source: GBIF
More photos
Questions people ask
When are Therion circumflexum wasps active?
Adults are on the wing from mid-June to September.
Source: Wikipedia
What do the females use to lay eggs?
Female wasps have a short spike that they use to insert eggs into caterpillars.
Source: Wikipedia
Which moths do they parasitize?
They target several moth species such as small engrailed, privet hawk, pine hawk-moth, pebble prominent and various owlet moths.
Source: Wikipedia
Same family (Ichneumonidae)
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Therion_circumflexum
Look it up elsewhere: GBIF · iNaturalist · BugGuide · Wikipedia
Text written 2026-10-28 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-28.