ichneumonid wasp

(Therion circumflexum)

Conservation Status
IUCN Red List

not listed

NatureServe

not listed

Minnesota

not listed

 
ichneumonid wasp (Therion circumflexum)
Photo by Babette Kis
 
Description

Therion circumflexum is a large, solitary, parasitic wasp. It occurs in Europe, North America, Japan, and Korea. It occurs throughout the United States, where it is most common in the east from Maine to Connecticut, west to Minnesota, and in the Pacific Northwest.

Adults are active from May to October. One study in California found them in oak chaparral and oak woodland habitats. Larvae are internal parasites on Lepidoptera caterpillars, mostly in the family Noctuidae, but also in the families Lasiocampidae, Geometridae, Notodontidae, and Sphingidae.

Adults are 916 to 1 (14 to 25 mm) in length.

On the female, the head is relatively large and mostly black. The upper front part of the head (frons), corresponding to the forehead, has a longitudinal, horn-like ridge (carina) in the middle. There is no carina on the face. The plate on the face (clypeus) is cut off (truncate) on the lower margin. It lacks a pointed projection or tooth in the middle. The face is mostly black, but the clypeus and the lower part of the cheeks (genae) are yellow; there is a broad, yellow, longitudinal stripe in the middle; and there is a narrow yellow line on the inner margin (orbit) of each compound eye. The eyes are hairless. The antennae have 51 to 57 segments. The two segments at the base (scape and pedicel) are black. The remaining segments (flagellomeres) are yellow.

The front part of the body (mesosoma) is mostly black. The upper plate on the first segment (pronotum) is black. It has a small, pointed tooth on the underside at the front margin. The large plate on the front part of the middle segment (scutum) is black. When viewed from above it is 1.4 to 1.5 times longer than wide. The lateral margins have a longitudinal impression, but this may be more or less discernible. The small plate on the rear part of the middle segment (scutellum) is usually yellow, rarely black. When viewed from the side it is moderately convex. The small plates covering the wing bases (tegulae) are yellow. The rear margin of the plate on each side of the middle thoracic segment (mesopleuron) is usually yellow, rarely black. The first abdominal segment (propodeum) is fused to the thorax giving the thorax the appearance of having four segments. The propodeum is rounded when viewed from above, flat when viewed from the side.

The remaining part of the abdomen (metasoma) is long and cylindrical. It has eight segments (tergites). The first tergite (T1) is slender and amber to dark amber. T2 is mostly amber but it is black on the upper side. T3 is entirely amber. T4 and T5 are mostly amber but are black on the underside. T6 through T8 are entirely black. The ovipositor rises in front of the tip of the abdomen, and it cannot be withdrawn. It is short, 0.4 to 0.7 times the length of the fourth segment (tibia) of the hind leg.

The wings are transparent and lightly tinted brownish. The veins are brown to yellow. On the forewing, the thickened leading edge (costal area) of the wing does not have a cell. The base of the cubital (cu) vein is lacking. There are two recurrent (backward-turning) veins forming a cell. The first submarginal cell and the first discoidal cell are fused into a single large discosubmarginal cell. The shape of the discosubmarginal cell is said to resemble a horse’s head and is sometimes called the “horsehead cell.”

The legs are long, slender, and mostly amber or yellow. The first segment (coxa) of each leg is black. On the hind leg, the outer quarter of the third segment (femur) is black, and the outer quarter of the hind tibia is brownish.

On the male, the antennae have 45 to 49 segments. The face is entirely yellow. The rear margin of the mesopleuron is black. On the hind legs, the first segment (coxa) is yellow on the underside in the middle.

 

Size

Total length: 916 to 1 (14 to 25 mm)

 

Similar Species

 
Habitat

 

Biology

Season

May to October

 

Behavior

 

 

Life Cycle

The female uses her needle-like ovipositor to insert an egg into the body of a living moth caterpillar. When the egg hatches, the larva consumes non-vital tissues of the host. When the host pupates, the wasp larvae kills the host and pupates within the host’s pupal shell, later emerging as an adult wasp.

 

Larval Hosts

Caterpillars, mostly in the family Noctuidae, but also in the families Lasiocampidae, Geometridae, Notodontidae, and Sphingidae.

 

Adult Food

 

Distribution

Distribution Map

 

Sources

24, 27, 29, 30, 82.

12/9/2024    
     

Occurrence

 

Taxonomy

Order

Hymenoptera (ants, bees, wasps, and sawflies)

Suborder

Apocrita (narrow-waisted wasps, ants, and bees)

Infraorder

Terebrantes

Superfamily

Ichneumonoidea (ichneumonid and braconid wasps)

Family

Ichneumonidae (ichneumonid wasps)

Subfamily

Anomaloninae

Tribe

Gravenhorstiini

Genus

Therion

   

Subordinate Taxa

 

   

Synonyms

Therion callosum

Therion circumflexus (misspelling?)

Therion curticorne

Therion japonicum

Therion laricis

Therion nigroscutellatum

Therion nigrum

Therion nipponicum

Therion occidentale

Therion ramidulum

Therion rubropictum

Therion unicolor

   

Common Names

This species has no common name. The common name of the family Ichneumonidae is Ichneumonid wasps, and it is applied here for convenience.

 

 

 

 

 

 

 

 

Glossary

Carina

An elevated keel or ridge.

 

Clypeus

On insects, a hardened plate on the face above the upper lip (labrum).

 

Coxa

The first segment of the leg of an insect, attaching the leg to the body, and connected to the trochanter. Plural: coxae.

 

Femur

On insects and arachnids, the third, largest, most robust segment of the leg, coming immediately before the tibia. On humans, the thigh bone.

 

Flagellomere

A segment of the whip-like third section of an insect antenna (flagellum).

 

Frons

The upper front part of an insect’s face, roughly corresponding to the forehead.

 

Gena

In insects: The area between the compound eye and the mandible; the cheek. In birds: The area between the the angle of the jaw and the bill; the feathered side (outside) of the under mandible. Plural: genae.

 

Mesosoma

In Hymenoptera: the front part of the body, consisting of all three segments of the thorax and the first segment of the abdomen, to which the wings are attached.

 

Pedicel

On plants: the stalk of a single flower in a cluster of flowers. On insects: the second segment of the antennae. On Hymenoptera and Araneae: the narrow stalk connecting the thorax to the abdomen: the preferred term is petiole.

 

Pronotum

The exoskeletal plate on the upper side of the first segment of the thorax of an insect.

 

Propodeum

In Hymenoptera: the last segment of the thorax, anatomically the first segment of the abdomen.

 

Scape

In plants: An erect, leafless stalk growing from the rootstock and supporting a flower or a flower cluster. In insects: The basal segment of the antenna.

 

Scutellum

The exoskeletal plate covering the rearward (posterior) part of the middle segment of the thorax in some insects. In Coleoptera, Hemiptera, and Homoptera, the dorsal, often triangular plate behind the pronotum and between the bases of the front wings. In Diptera, the exoskeletal plate between the abdomen and the thorax.

 

Scutum

The forward (anterior) portion of the middle segment of the thorax (mesonotum) in insects and some arachnids.

 

Tegula

A small, hardened, plate, scale, or flap-like structure that overlaps the base of the forewing of insects in the orders Lepidoptera, Hymenoptera, Diptera, and Homoptera. Plural: tegulae.

 

Tergite

The upper (dorsal), hardened plate on a segment of the thorax or abdomen of an arthropod or myriapod.

 

Tibia

The fourth segment of an insect leg, after the femur and before the tarsus (foot). The fifth segment of a spider leg or palp.

 

 

 

 

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Babette Kis

Therion circumflexum ichneumonid wasp

The body of Therion circumflexum, an ichneumonid wasp, measures about an inch long. This very noticeable wasp was flying around vegetation at Barnes Prairie, Racine Co., WI and was difficult to photograph. On May 30, 2024, it landed, so I was able to get a few photos.

ichneumonid wasp (Therion circumflexum)   ichneumonid wasp (Therion circumflexum)

Alfredo Colon

ichneumonid wasp (Therion circumflexum)   ichneumonid wasp (Therion circumflexum)
     
ichneumonid wasp (Therion circumflexum)    
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Other Videos

Therion? - Therion circumflexum
MrAlanC

About

Jun 2, 2024

'Fairy wasp' Therion circumflexum, Dart Valley Woods, Dartmoor, Devon July 2024
John Walters

About

Jul 24, 2024

Ichneumon 'Fairy wasp' Therion circumflexum (kindly identified by Gavin Broad British Museum Natural History). Flying slowly around Bracken, Hazel, Honeysuckle and Birch probably searching for caterpillars to lay her eggs inside. Dart Valley Woods, Dartmoor, Devon. July 2024

Therion circumflexum (Ichneumonidae-Hymenoptera)
flhorea01

About

Sep 30, 2015

Therion circumflexum. Un insecte très, très, très volatile. Ce sont des insectes depuis longtemps utilisés en lutte biologique

En Europe on en collectait des larves dans le sol aux pieds des arbres forestiers pour les répandre dans les plantations sylvicoles ou de fruitiers.

Ce sont des insectes hyménoptères térébrants relevant, avec les Braconidae, de la super-famille des Ichneumonoidea.

Cette grande famille comprend 35 sous-familles regroupant plus de 60 000 espèces (Wikipedia).

(Translated) Therion circumflexum. A very, very, very volatile insect. These are insects that have long been used in biological control. In Europe, their larvae were collected in the soil at the foot of forest trees to spread them in forest or fruit plantations. They are boring hymenopteran insects that, along with the Braconidae, belong to the superfamily Ichneumonoidea. This large family includes 35 subfamilies containing more than 60,000 species (Wikipedia).
Order Hymenoptera
Superfamily Ichneumonoidea
Family Ichneumonidae
Genus Therion
Species Therion circumflexum

 

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Babette Kis
5/30/2024

Location: Barnes Prairie, Racine Co., WI

The body of Therion circumflexum, an ichneumonid wasp, measures about an inch long. This very noticeable wasp was flying around vegetation at Barnes Prairie, Racine Co., WI and was difficult to photograph. On May 30, 2024, it landed, so I was able to get a few photos.

ichneumonid wasp (Therion circumflexum)

Clare
6/9/2020

Location: Plymouth, MN 55442

I saw the very same ichneumon wasp that Alfredo Colon shows in the photo on your website (pasted portion of photo below)….  I have never seen one before and so searched for it and came across your website.  This was the only site I could find with a photo of what I had seen, Thanks!

Alfredo Colon
8/16/2018

Location: Woodbury, Minnesota

ichneumonid wasp (Therion circumflexum)
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Created: 12/10/2024

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