none Female Trioxys indicus , an aphidiid parasitoid of the pigeonpea aphid Aphis craccivora , responded to aqueous extract (having kairomones) of the host topically sprayed onto host-infested leaves by examining such area intensely with their antennae. Results indicate that the use of kairomones can significantly increase the parasitisation rates only at the appropriate host density. At low host density, application of kairomones may be disadvantageous. Reproduction; Reproductive behaviour; Behaviour; Communication; Chemical signals; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Host parasite relationships; Ecology; Population dynamics; Population structure Trioxys indicus (Braconidae); Oviposition; Hemipteran host kairomone relations, effect of host density; Hemipteran hosts; Aphis craccivora; Host kairomone effect on reproduction; Host recognition; Aphis (Hemiptera) host, effect of host kairomone & density; Reaction of parasite to host; Hemipteran host kairomone effect on reproduction, host density relations; Population sex ratio; Offspring, effect of hemipteran host density & kairomone extract Aphis craccivora (Aphidoidea); Pheromones; Hymenopteran parasites; Trioxys indicus; Kairomone extract & density effect on parasite reproduction; Host recognition; Trioxys (Hymenoptera) parasite, effect of host kairomone & density; Reaction of parasite to host; Kairomone effect on hymenopteran parasite host recognition & reproduction