Searching strategies and attack rates of parasitoids of the ash bark beetle ( Leperisinus varius ) and its relevance to biological control

.1 Point estimates of parasitoid behaviour indicated that braconid parasitoids of the bark beetle, Leperisinus varius , spend 70% of their host searching time stationary on the bark surface, in sharp contrast to the chalcidoid parasitoids which spend 60–70% of their host searching time moving across the bark surface. 2 Aggressive encounters between searching parasitoids are common and the data suggest that they do not occur at random. 3 The chalcidoid parasitoids, Cheiropachus quadrum and Eurytoma morio , are more frequently involved in aggressive encounters than expected and can displace ovipositing individuals of other species. 4 Attack rates for the parasitoids were estimated to vary from two hosts per day for the braconid Coeloides filiformis to four hosts per day for E.morio , and net reproductive rates vaned from 6.3 for C.filiformis to 0.8 for Coeloides melanotus . 5 These data suggest that while all parasitoids of the scolytid can act as primary parasitoids, at least some of the chalcidoid parasitoids are facultative cleptoparasitoids and should be avoided in classical biological control introductions.