Behavioural Response of Specific Larval Endoparasitoid, Apanteles machaeralis (Wilkinson) to Volatile Cues from its Host Insect, Diaphania indica (Saunders) and the Host Plant ( Cucumis sativus L.)

Apanteles machaeralis (Wilkinson), a braconid specialist larval endoparasitoid of Diaphania indica occurs naturally causing significant levels of parasitism.  The present study explores the response of the A. machaeralis to odour cues from D. indica damaged cucumber plant as well as host larvae. Different odour treatments namely, D. indica larval body volatiles (T₁), volatiles from larval excreta (T₂), volatiles from larvae + excreta (T₃),  volatiles from D. indica body wash (T₄), volatiles from the healthy, mechanically damaged and D. indica infested cucumber plants (HIPVs) were collected using headspace analysis and the response of female A. machaeralis was studied using olfactometer assays. Results of the study conclusively indicated that A. machaeralis is highly attracted to host larval body wash as parasitic wasps spent significantly more time made more entries into the treated region in single as well as dual choice assays. The electoantennographic response (EAG) further supported the olfactometer bioassays.  The GC-MS analysis revealed significant differences in the volatile emissions of different treatments studied. The utilization of host insect body cues and HIPVs in the host recognition by the specialist endoparasitoid A. machaeralis is discussed in detail.