Development of Tiphodytes gerriphagus (Hymenoptera : Scelionidae) in Limnoporus dissortis eggs (Hemiptera : Gerridae)

Investigations of preimaginal development in Tiphodytes gerriphagus Marchal reveal two larval instars, based on counting exuviae and comparing mandibl e length during development within Limnoporus dissortis Drake & Harris eggs . Tiphodytes gerriphagus eggs are stalked, as is typical of scelionids, and are 282.6 +/- 3.48 mu m (mean +/- SE) long. The chorion ruptures at 8-9 h postoviposition and releases a nonfeeding embryo into the host. Feeding beg ins at 18-20 h postoviposition, after the embryonic cuticle is shed and a f ully differentiated and active larva is released. The first larval stage is teleaform and lasted up to 5 days postoviposition, and its total length in creased from 183.6 +/- 3.35 to 517.0 +/- 14.67 mu m. The second larval stag e is hymenopteriform and lasted from 5 to 13 days postoviposition, and grew from 920.2 +/- 24.65 to 1352.4 +/- 11.89 mu m total length before pupating . The pupal period lasted about 11 days, with male pupae being shorter and thinner than female pupae. These findings differ from previous descriptions of T.: gerriphagus, and it is suspected that the first instar was mistaken ly divided into two stadia. The sex ratio under laboratory conditions was f emale biased (22% males), and males were smaller but did not emerge signifi cantly earlier than females.