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PestNet is a network that helps people worldwide obtain rapid advice and information on crop protection, including the identification and management of plant pests. It started in 1999. Anyone with an interest in plant protection is welcome to join. PestNet is free and is moderated, ensuring that messages are confined to plant protection.
March 2005. This unknown parasitoid hatched from a caterpillar feeding on brassicas. The body length of the wasp is 5 mm (ovipositor not included). Unfortunately, the host is not known as the samples were part of a screening survey for cabbage pest parasitoids. Possibilities are: the tropical armyworm, Spodoptera litura and the large cabbage moth, Crocidolomia binotalis. The diamond back moth, Plutella xylostella, was also abundant, but is probably too as the host.
It was thought to be Meteorus pulchricornis (Wesmael) (Hymenoptera: Braconidae: Euphoridae). It is very distinctive, in particular the pupal cocoon which is suspended by a thread anchored on foliage.
It is beign studied at Food & Crops, New Zealand, to determine whether it is a pest or beneficial insect. It is an extreme generalist larval parasitoid attacking any exposed lepidopteran larvae. It has been reared from every lepidopteran species collected on vegetable crops (about 30 species from 8 families of Lepidoptera), except Pieris rapae (white butterfly). On brassicas, it readily attacks Helicoverpa armigera and Spodoptera litura, but it has also been reared from Plutella xylostella. We don’t have Crocidolomia in New Zealand. From micro Lepidoptera such as DBM, the cocoons are very small which would be a clue for you. Being 5 mm long, it probably came from Spodoptera, not DBM. It attacks small larvae (2nd instar) and emerges from about medium the 4th instar stage, not letting the host grow very large.
There are only females in New Zealand (thelytokous) which suggests that it originated in Asia where there are only females, whereas there are males and females in Europe (arrhenotokous = biparental). The one in the photo is a female.
Our concern is that is it is penetrating native habitats and attacking native fauna and upsetting native parasitoids, etc. In cropping areas of New Zealand, it is displacing our introduced larval parasitoids of H armigera, but not decreasing levels of parasitism. It attacks many native species in modified habitats, too, and it is commonly reared from noctuids and geometrids.
More details can be found in New Zealand Journal of Zoology (2004) 31: 33-44, J Berry & G Walker. Aabstracts for this journal, plus other journals are available at: www.rsnz.org/publish/abstracts.php. Note also that pdfs are available, without cost, of articles in early volumes of New Zealand Journal of Zoology (1994-2003) and others.