ICHNEUMONIDAE: : Megarhyssa Ashmead 1900
Diagnosis:Megarhyssa is easily recognised because of its large size, 2-3cm, very long ovipositor and colourful metasoma.
Characteristics of Megarhyssa include: 1. Body size >20mm; 2. Position of spiracle on T1 at, close to, or before centre; 3. Shape of aerolet in forewing is petiolate; 4. Colour of faceis not all black; 5. Metasoma not compressed or dorsal-ventrally; 6. Size of ocelli are small; 8. Length of ovipositor is very long, longer than body; 9. Wings present; 10. Colour of wings hyaline (clear); 11. Sternaulus absent; 12. Shape of face in lateral view is flat or only weakly bulging; 13. Sternite on T1 (viewed laterally) not extending past spiracle; 14. Shape of T1(viewed laterally) is evenly curved; 15. Number of teeth in mandibles 2; 16. Metasoma with colourful spots; 17. Length of T1 less than T2; 18. Sculpture on mesoscutum with transverse striations (wrinkles); 19. Width of T1 (viewed dorsally) of uniform width (slightly widening posteriorly); 20. Glymma on T1 absent; 21. Sculpture on metasoma smooth with a glossy appearance (highly polished, no punctures); 22. Propodeum reaching past coxal insertion, but not reaching halfway along metacoxae.
Similarity to Other TaxaMegarhyssa is easily recognised because of its large size, 2-3cm, very long ovipositor and colourful metasoma. Megarhyssa can only be confused with a native species, Certonotus fractinervis . Certonotus has distinct yellow spots on top of the metasoma, whereas Megarhyssa has these spots on the sides of the metasoma.
Distribution in NZ
North Island: AK, BP, HB, WO. South Island: NN.
Species in NZOne biological control agent, Megarhyssa nortoni nortoni (Cresson 1864).
Biology & hostsA Holarctic and Oriental genus. Megarhyssa nortoni nortoni was introduced into New Zealand in 1964 to control infestations of Sirex noctilio in Pinus radiata plantations (Nuttall 1980). Together, with other parasitoids and parasites, it achieves very good control.
Sources of informationGauld ID. 1984. An Introduction to the Ichneumonidae of Australia. London, British Museum (Natural History). 413 p.
Nuttall MJ. 1980. Insect parasites of Sirex (Hymenoptera: Ichneumonidae, Ibaliidae, and Orussidae). Forest Timber Insects in New Zealand 47. Forest Research Institute, New Zealand Forest Service. 12 p.
Parrott AW. 1952. New Zealand Ichneumonidae. II. Tribe Echthromorphini (Pimplinae). Transactions of the Royal Society of New Zealand (Zoology) 80: 155-170.
Parrott AW. 1962. Notes and synonymy of New Zealand Ichneumonidae. Subfamily Pimplinae. Transactions of the Royal Society of New Zealand (Zoology) 1: 349-353.
CitationWard DF & Schnitzler FR. 2013. Ichneumonidae of New Zealand. Genus Megarhyssa http://ichneumonidae.landcareresearch.co.nz
Accessed: 22 October 2019