BIOLOGY OF COELOIDES-SORDIDATOR (HYMENOPTERA, BRACONIDAE), A POSSIBLECANDIDATE FOR INTRODUCTION AGAINST PISSODES-STROBI (COLEOPTERA, CURCULIONIDAE) IN NORTH-AMERICA

Various aspects of the biology of Coeloides sordidator, an ectoparasit oid of pine weevils of the genus Pissodes, were studied When reared in the laboratory on P. castaneus, females preferred to oviposit on thir d and fourth instar larvae in galleries, but ovipositions were also ob served on second instars and prepupae. Pupae were not accepted as host s. At 23 degrees C and a 16 h day length, pre-imaginal development las ted 15-20 days. For each parasitoid population tested between 8 and 28 % of the individuals diapaused as prepupae in cocoons. The rate of dia pause was not influenced by the photoperiod during larval development. In contrast, diapause was induced by a short day photoperiod on paren ts before and during oviposition and by low temperatures during the la rval stage. Diapause termination was achieved by cold storage at 2 deg rees C for at least 8 weeks. Rearing of C. sordidator on P. castaneus under natural conditions showed that in the Swiss Jura it is mainly un ivoltine, with less than 10% of the parasitoids emerging for a second generation. When C. sordidator females were offered healthy P. castane us larvae and larvae parasitized by the braconid endoparasitoid Eubazu s semirugosus, there was no evidence that they were able to discrimina te between healthy and parasitized hosts. The potential of C. sordidat or as a biological control agent against the North American species P. strobi is discussed.