Oviposition behaviour, influence of experience on host size selection, andniche overlap of the solitary Leptomastix epona and the gregarious Pseudaphycus flavidulus, two endoparasitoids of the mealybug Pseudococcus viburni

Oviposition behaviour and host size selection of the solitary parasitoid Le ptomastix epona (Walker) and the gregarious Pseudaphycus flavidulus (Brethe s) [both Hymenoptera: Encyrtidae] were examined on five size classes of the mealybug Pseudococcus viburni (Signoret) [Hemiptera: Pseudococcidae]. The host size classes mostly consisted of one stage (first, second, third insta r nymph, young adult and preovipositing adult) and were presented together to wasps of either parasitoid species. Both parasitoid species locate the h ost by drumming the surface of the patch with the antennae. Leptomastix epo na seems to use mainly the antennae to examine the host but P. flavidulus m ay accept or reject a host for oviposition after antennation or insertion o f the ovipositor. Leptomastix epona attempts oviposition in all the host st ages from second instar nymphs but P. flavidulus includes first instar. Bot h parasitoid species select mainly larger hosts (>1 mm, third instar nymphs ) to oviposit but P. flavidulus is able to parasitize more second instar ny mphs compared to L. epona. Female wasps of L. epona may host feed on small mealybugs (second and third instar nymphs) that they do not use for oviposi tion. Oviposition experience of either parasitoid species for 24 hours does not influence host size selection on patches with hosts of similar mixed s izes. Oviposition decisions are independent of the host sizes of the preced ing ovipositions. Implications about stability of a single parasitoid - hos t system and the success of biological control of the mealybug were discuss ed in respect of the developmental refugia of the two parasitoid species. N iche overlap of the two parasitoid species was discussed with a view to giv ing an insight into a single or multiple introduction.