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The biology of Pseudorhyssa sternata Merrill (Hym., Ichneumonidae), a cleptoparasite of Siricid woodwasps

Published online by Cambridge University Press:  10 July 2009

J. P. Spradbery
Affiliation:
Sirex Biological Control Unit (Division of Entomology, C.S.I.R.O.), Silwood Park, Sunninghill, Ascot, Berkshire

Extract

The life-history of Pseudorhyssa sternata Merrill was investigated under natural and artificial conditions.

When P. sternata and Rhyssa persuasoria (L.) females were present on Siricidinfested logs, P. sternata observed the primary parasite making drill shafts, and after the primary withdrew its ovipositor and moved away, P. sternata located the shaft and inserted its ovipositor to gain access to the host. P. sternata was able to locate R. persuasoria drill shafts aged 1–38 days.

P. sternata females were stimulated to oviposition behaviour when presented with paper drilled by R. persuasoria, and this response was enhanced by the presence of wet Siricid frass, or the symbiotic fungus of Siricids. Ovipositor probing was also made through artificial holes into frass. Bioassay of R. persuasoria vaginal and venom glands resulted in considerable probing into filter paper impregnated with vaginal gland extract.

It was concluded that P. sternata females probably locate Siricid-infested trees by responding to a generalised stimulus that is potent in larval frass, and which possibly derives from the symbiotic fungus. The cleptoparasite probably finds the drill-shaft by responding to a secretion of the vaginal gland of the primary parasite.

Type
Original Articles
Copyright
Copyright © Cambridge University Press 1969

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References

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