ICHNEUMONIDAE: : Diadromus Wesmael 1845
Diagnosis:Females of Diadromus collaris have a distinct body colouration of black (head, propodeum, T1, end metasoma), witht the rest of body orange. The head/body of males is black and the metasoma is striped brown/black.
Characteristics of Diadromus include: 1. Body size <10mm; 2. Position of spiracle on T1 clearly behind the centre; 3. Shape of aerolet in forewing pentagonal (open or closed); 4. Colour of face only black; 5. Metasoma compressed dorsal-ventrally; 6. Size of ocelli small; 7. Length of antennae shorter than body; 8. Length of ovipositor distinct but very short; 9. Wings present; 10. Colour of wings hyaline (clear); 11. Sternaulus absent; 12. Shape of face in lateral view flat or only weakly bulging; 13. Sternite on T1 not extending past spiracle; 14. Shape of T1 evenly curved; 15. Number of teeth in mandibles 2 (but often appears as 1); 16. Metasoma of females bicoloured (black/orange); Metasoma of males striped (brown, black); 17. Length of T1 less than T2; 18. Sculpture on mesoscutum finely pitted, somewhat polished; 19. Width of T1 (viewed dorsally) anterior part slender often parallel, strongly widening behind spiracle; 20. Glymma on T1 absent; 21. Sculpture on metasoma smooth with a semi-glossy or satin appearance at least on T2; 22. Propodeum reaching past coxal insertion, but not reaching halfway along metacoxae.
Distribution in NZ
North Island: AK, BP, WI. South Island: NN, CO.
Species in NZOne introduced biological control agent, Diadromus collaris (Gravenhorst 1829).
Biology & hostsDiadromus collaris was introduced into New Zealand in the mid 1900s as a biological control agent against the diamondback moth, Plutella xylostella (Lepidoptera: Yponomeutidae). It is considered to give good control (Cameron et al. 1989).
Sources of informationCameron PJ, Hill RL, Bain J and Thomas WP. 1989. A Review of Biological Control of Invertebrate Pests and Weeds in New Zealand 1874-1987. Technical Communication No 10. CAB International Institute of Biological Control. DSIR Entomology Division. 424 p.
Gauld ID. 1984. An Introduction to the Ichneumonidae of Australia. London, British Museum (Natural History). 413 p.
CitationWard DF & Schnitzler FR. 2013. Ichneumonidae of New Zealand. Genus Diadromus http://ichneumonidae.landcareresearch.co.nz
Accessed: 12 July 2020