ichneumonid wasp

(Diadegma insulare)

Conservation Status
ichneumonid wasp (Diadegma insulare)
Photo by Alfredo Colon
  IUCN Red List

not listed

 
  NatureServe

NNR - Unranked

 
  Minnesota

not listed

 
           
           
           
           
           
           
           
 
Description
 
 

Diadegma insulare is a small, native, common but little reported, parasitic wasp. It occurs in North America from New Hampshire to Florida, west to southern British Columbia and Texas, in California, and in Hawaii. It also occurs in the West Indies and in Mexico south to Venezuela. It is the only Diadegma species native to the Nearctic realm.

Diamondback moth (Plutella xylostella) is a major pest of cruciferous agricultural crops, including broccoli, brussels sprouts, cabbage, cauliflower, collard greens, kale, kohlrabi, mustard, rutabaga, turnips, Bok choy, and Chinese cabbage. Diadegma insulare is considered a beneficial insect because it parasitizes the larvae of the diamondback moth. It not only kills the moth larvae, but before doing so it reduces the amount of crop the larva consumes by up to 80%.

Like many other genera in the subfamily Campopleginae, there are very few or no distinctive features that will confirm placement in the genus Diadegma.

The female is slender, black, and 316 to ¼ (4.80 to 5.74 mm) in length.

The head is black. The antennae are long and black. They have 20 to 23 segments (flagellomeres) beyond the scape and pedicel at the base. The subcircular keel between the top of the head and the eyes (occipital carina) is complete. The plate on the face (clypeus) is no more than two times as wide as deep. It smoothly merges with the rest of the face. It is uniformly convex and does not have a swelling across the middle or a tooth on the lower margin.

The front part of the body (mesosoma) is black.

The rear part of the body is mostly black. There is usually brown to orange on the underside of the second, third, and fourth segments (tergites T2, T3, and T4) or on the sides of T2 and beyond. Sometimes T2 and T3 are tinged with brown. The metasoma is rarely entirely black. The rear margin of T7 is slightly notched. The rear margins of T5 and T6 are not notched. The ovipositor extends beyond the tip of the metasoma.

The legs are striped dark brown and yellow. The fourth segment (tibia) of the hind legs has two spurs. It is light yellow to yellow and has a brown band at the base and another just above that (subbasal).

The male is 316 to ¼ (4.80 to 6.48 mm) in length. The antennae have 23 to 25 flagellomeres. On the metasoma, T7 is not notched. The male is otherwise similar to the female.

 
     
 

Size

 
 

Female total length: 316 to ¼ (4.80 to 5.74 mm)

Male total length: 316 to ¼ (4.80 to 6.48 mm)

 
     
 

Similar Species

 
     
     
 
Habitat and Hosts
 
 

Agricultural crops in the Brassicaceae family.

Diamondback moth (Plutella xylostella)

 
     
 
Biology
 
 

Season

 
 

Four generations per year in the north: April to October

Six generations per year in the south: year round

 
     
 

Behavior

 
 

 

 
     
 

Life Cycle

 
 

The female inserts (oviposits) a single egg into a moth larva. She may lay up to 800 eggs in her short lifetime. When the egg hatches, the wasp larva feeds internally on its host but does not immediately kill it. As the host matures, it becomes sluggish and consumes 80% less of the crop than its non-parasitized kin. It survives long enough to spin a cocoon. The wasp larva then kills its host, emerges from the host body, and spins its own cocoon within the host cocoon.

Pupae overwinter in their cocoons in crop debris.

 
     
 

Larva Food

 
 

Diamondback moth larvae

 
     
 

Adult Food

 
 

Flower nectar

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 29, 30, 82, 83.

There are very few records of this wasp anywhere, and there are no records at all in Minnesota except for the one on this page. However, according to a beneficial insect profile published online by the University of Minnesota Department of Entomology:

From 1994 to 2003, D. insulare parasitized 62-82% of diamondback moth collected in cabbage plants in Minnesota.

 
  10/15/2023    
       
 

Occurrence

 
 

Common

 
         
 
Taxonomy
 
 

Order

Hymenoptera (ants, bees, wasps, and sawflies)  
 

Suborder

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

Superfamily

Ichneumonoidea (ichneumonid and braconid wasps)  
 

Family

Ichneumonidae (ichneumonid wasps)  
 

Subfamily

Campopleginae  
 

Tribe

Limneriini  
 

Genus

Diadegma  
       
 

Diadegma is a large genus of ichneumonid wasps. Global Biodiversity Information Facility (GBIF) lists 228 species worldwide but it shows only Diadegma semiclausum occurring in North America. iNaturalist has reports of a second species, Diadegma semiclausum. BugGuide.net lists the genus and the “stenosomum species complex”, but it lists no members of that species complex, in fact it lists no Diadegma species. A recent review of the genus (Azidah A.A., 2000) states lists the distribution of Diadegma semiclausum as “Palaearctic, and introduced into many other parts of the World, but probably not yet successfully into Nearctic or Neotropical regions.” If that remains true, then Diadegma insulare is the only species in the genus occurring in North America, and reports from iNaturalist are misidentifications.

 
       
 

Synonyms

 
 

Diadegma congregator

Diadegma hellulae

Diadegma insularis

Diadegma plutellae

Diadegma polynesiale

Diadegma pygmaeum

 
       
 

Common Names

 
 

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

 

 

 

 

 

 

 

 

 

Glossary

Carina

An elevated keel or ridge.

 

Clypeus

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

 

Flagellomere

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

 

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.

 

Metasoma

In Hymenoptera: the armored rear part of the body, consisting of the second segment of the abdomen and all segments posterior to it.

 

Scape

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

 

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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Alfredo Colon

 
    ichneumonid wasp (Diadegma insulare)      
           
 
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Other Videos
 
  Diadegma insulare parasitando Palomilla Dorso de diamante
Organismos Benéficos
 
   
 
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Oct 1, 2018

Diadegma insulare parasitando Palomilla Dorso de diamante

Créditos
J. Manuel M.
Organismos Benéficos para la Agricultura

 

 

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  Alfredo Colon
6/2/2021

Location: Woodbury, MN

ichneumonid wasp (Diadegma insulare)  
           
 
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Created: 10/15/2023

Last Updated:

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