EGGSAC PARASITISM OF MONEY SPIDERS (ARANEAE, LINYPHIIDAE) IN CEREALS,WITH A SIMPLE METHOD FOR ESTIMATING PERCENTAGE PARASITISM OF ERIGONE SPP EGGSACS BY HYMENOPTERA

Observations on parasitism of eggsacs of the linyphiid spiders Erigone spp., Oedothorax spp., Bathyphantes gracilis and Lepthyphantes tenuis by four species of hymenopterous parasitoids in a field of winter whe at are described. The dominant parasitoids emerging from eggsacs were Gelis festinans (Ichneumonidae) and Baeus sp. (Scelionidae). Percentag e parasitism of introduced and naturally occurring eggsacs was compare d for the months of May, June and July. No eggsacs of Oedothorax spp. and B. gracilis were parasitized. Oedothorax spp. females were observe d, in both laboratory and field, to guard their eggsacs efficiently ag ainst attack by parasitoids. The percentage of naturally occurring egg sacs of Erigone spp. parasitized by G. festinans was not significantly different from the percentage parasitism of eggsacs introduced into t he field in modified Petri dishes; the Petri dish introduction method therefore provides a simple and efficient means of assessing parasitis m in the field.