Published online by Cambridge University Press: 10 July 2009
Larvae of Pimpla instigator (F.) were found to pass through five larval instars during development. Initial studies of external morphology identified only three morphological groups: the primary larva (L1) the intermediate larvae (L2−4) and the final instar larvae (L5). Biometrical study of the maximum head width, width of buccal mask, inter-metatentorial distance and diameter of spiracles permitted morphological separation of all five larval instars. Under a 16 h photophase (at 25±1°C; 70±10% r.h.) and an 8 h scotophase (at 15±l°C; 80±10% r.h.) the 2nd, 3rd and 4th larval instars were found to last about 24 h each, and the 5th instar 9±1 days. Progressive development of the genital buds during the 5th instar and prepupal stages facilitated sexing of the larvae.