T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Wasp (Samurai wasp) Trissolcus japonicus

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Platygastridae
Genus: Trissolcus
Species: T. japonicus
Binomial name: Trissolcus japonicus
Synonym: Trissolcus halyomorphae
Common name: Samurai wasp

Trissolcus japonicus is a tiny parasitoid wasp species in the family Platygastridae. It is chiefly known for as an egg parasitoid of Halyomorpha halys (brown marmorated stink bug). 

Small numbers of Trissolcus japonicus has been imported into New Zealand under strict quarantine conditions and they are kept in a secure facility where authorities are conducting research to determine if this wasp will have any impact on native flora and fauna. As of April 2018, no decision on their release has been made. 
Halyomorpha halys is now in New Zealand and it is estimated in the future it will cause hundreds of millions of dollars of losses and the loss of overseas markets if it becomes established here. It eats apples, peaches kiwifruit, corn, tomatoes, cherries, wheat, maize and more.

The female wasp deposits its eggs into the eggs of the stink bug. As the wasp larvae develop, they kill the stink bug eggs. A single adult wasp emerges from each stink bug egg. It is said to be one of the most effective biological controls of the brown marmorated stink bug.

Trissolcus japonicus adults are small black wasps (1.0-2.0 mm long) (Dieckhoff and Hoelmer 2014). The size of the wasp depends on the size of the host egg from which it emerged (Medal and Smith 2015). The female is slightly larger than the male by 0.1-0.2 mm. The head is large, broader than the thorax, and glossy with a few punctures. The 11-segmented antennae are brown-black, the scape and pedicel yellow-brown. The mandibles are reddish brown. The legs are mostly black with the tibia and tarsi yellow-brown to pale yellow (Hirashima et al. 1981). The wings are transparent with pale yellow veins. The abdomen is broadly oval and longer than the thorax (Ashmead 1904). The ovipositor is barely protruding.
Trissolcus japonicus deposits eggs singly within eggs of the brown marmorated stink bug. An average female Trissolcus japonicus contains 42 eggs in her ovaries at any one time, enabling her to parasitise an entire brown marmorated stink bug egg mass (Yang et al. 2009). Females chemically mark the egg in which they oviposit and will defend the egg clutch against other rival parasitoids. Males will commonly emerge first, wait atop the egg mass for the female to emerge, and then mate with females as they emerge. The female to male ratio is approximately 5.5:1.0 (Yang et al. 2009). The parasitoid can have up to ten generations per year, whereas their host generally has one to two generations a year.

A video on the 
Samurai wasp. https://www.youtube.com/watch?v=rbdXiiM538I

Female Trissolcus japonicus, lateral view 

Female Trissolcus japonicus, dorsal view.

Adult emerging from a brown marmorated stink bug Halyomorpha halys egg.

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/