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Crops > Vegetables > Crucifers > Chinese cabbage > Meteorus pulchricornis, Cook Is
March 2005. This unknown parasitoid hatched from a caterpillar feeding on brassicas in Cook Islands. 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 small to be 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 being 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. Crocidolomia is not present in New Zealand. From microlepidoptera such as Diamond back moth, the cocoons are very small which would be a clue. Being 5 mm long, it probably came from Spodoptera, not DBM. It attacks small larvae (2nd instar) and emerges from the 4th instar, not letting the host grow very large.
There are only females in New Zealand (thelytokous) which suggests that it originated in Asia where only females are known, whereas there are males and females in Europe (arrhenotokous = biparental). The one in the photo is a female.
The concern is that is it penetrating native habitats and attacking native fauna and upsetting native parasitoids. In cropping areas of New Zealand, it is displacing 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. Abstracts 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.