Flight by Listronotus bonariensis (Kuschel) in Canterbury, New Zealand varied greatly both within and between seasons; no winter flight was detected between mid-May and mid-August. Predisposing conditions for flight were found to be >19ЊC, rh <81% and windspeed <10.8 km h -1 . Three flight phases with different characteristics were identified when approximately equal numbers of weevils were trapped. These were between mid-August and early December (overwintered weevils), between early December and mid-March (first summer generation weevils) and mid-March and mid-May (first and second generation weevils). The proportion of individuals with developed flight musculature was c. 8% in the first phase and 30% in the last phase; muscle development was delayed in the midphase. First phase weevils with flight muscles were c. 20 times more likely to fly than those in the last. A very weak inverse relationship was observed between developed flight musculature and the presence or absence of eggs. Similarly, there was a very weak inverse relationship between weevil ground densities and the proportion with developed flight muscles. Levels of parasitism by Microctonus hyperodae Loan amongst trapped weevils were far less than that on the ground, indicating that it inhibits flight and may explain the relatively slow dispersal of the parasitoid. It was concluded that the adaptive implications of flight could be linked to escape responses from desiccating microclimates rather than dispersal from crowded habitats.

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The method whereby equal numbers of seven ecotypes of the parasitoid Microctonus hyperodae Loan (Hymenoptera: Braconidae, Euphorinae) were reared and released is described along with the reasons for doing so. This was achieved by variably intense rearing effort depending on the number of founder females in that particular ecotype.The parasitoid was released in three regions of New Zealand as a control agent of the Listronotus bonariensis Kuschel (Col. : Curculionidae), a severe pest of New Zealand pastures. It was later recovered from all three regions.

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The behaviour of the parasitoid Microctonus hyperodae Loan was studied under quarantine conditions to determine its likely host range in New Zealand. The species was imported from South America as a potential biological control agent of Argentine stem weevil, Listronotus bonariensis (Kuschel).The study involved systematic evaluation of the parasitoid's behaviour when exposed to 24 non-host weevil species ; all but three of these were native to New Zealand. Of those tested, four were found to sustain some M. hyperodae development. However, further examination showed that in all but one species, Irenimus aequalis (Broun), parasitoid development was impeded, with up to 50 % of the larvae becoming encapsulated. Overall, those weevil species that were attacked produced only 19 % of the parasitoids derived from L. bonariensis controls.As an adjunct to this quarantine study, a review of the habitats of the native weevil and target pest populations indicated that refugia would probably exist for native alpine species.L aequalis was not considered to be threatened by M. hyperodae as this weevil has benefited from the advent of European agricultural systems to the extent that it is now recognised as a minor pest. In view of its relatively oligophagous behaviour, the parasitoid was recommended as suitable for release. KEY-WORDS :Microctonus hyperodae, New Zealand, host range, habitat separation.