A. L. Prasuna

Electroantennogram responses of Apanteles obliquae (Hym., Braconidae) to various infochemicals

Abstract:  The electroantennogram recording technique (EAG) was used to study the olfactory sensitivity of Apanteles obliquae (Hym., Braconidae), a gregarious larval endoparasitoid of Spilosoma obliqua (Walker) (Lep., Arctiidae), to 25 general plant volatiles belonging to alcohol, aldehyde and terpenoid groups and also to volatiles from the host and plant–host complex. The EAG data indicated different olfactory sensitivity between the sexes, not only to individual plant volatiles but also to the volatiles from host and plant–host complex. Females were found to be more responsive than males. However the synthetic sex pheromone blend of the host insect elicited similar EAG responses in both sexes. The EAG data of the present study is correlated with the reported behaviour observed in other parasitoids.

Trichopria khandalus (Hym., Diapridae): a new biocontrol agent of the uzifly Exorista bombycis (Dipt., Tachinidae)

Biological control of the silkworm pest (Exorista bombycis) was partly successful by using a new hymemopteran biocontrol agent Trichopria khandalus, recovered from the environs of a cocoon market in Hindupur district of Andhra Pradesh (India). T. khandalus is a tiny (1–1.5 mm) endoparasite, the females were found to parasitize the uzifly puparia. The progeny developed inside the uzi pupa, and the adults (140–160 individuals from a single pupa) emerged after about 18–25 days depending on the seasonal extrinsic factors. The lift cycle of T. khandalus averaged 32 days. Due to the favourable sex ratio (2:3 male/female) and high preference to parasitize uzi puparia it is qualified as a good biocontrol agent for the control of E. bombycis. Prospects for utilizing this hyperparasite to manage and eliminate the uzi populations are discussed in the light of its data on biology, and easily manageable mass multiplication in the insectary.

Electrophysiological and behavioural responses of groundnut seed beetle Caryedon serratus (Olivier) (Coleoptera: Chrysomelidae) to conspecific and groundnut seed chemical cues

The olfactory and behavioural responses of groundnut seed-beetle, Caryedon serratus Olivier to semiochemicals isolated from conspecific insects as well as from groundnut seed headspace volatiles were investigated by coupled Gas Chromatography-Electroantennogram (GC-EAD) and Y-tube olfactometer bioassays. Significant orientation responses of male bruchids to the headspace volatiles from females and orientation responses of both sexes of seed beetles to headspace volatiles from male extracts confirm the existence of both sex and aggregation pheromone systems in C. serratus. Coupled GC-EAD analyses of headspace volatiles of female extract revealed seven bioactive peaks with strongest antennal responses of males towards flame ionization (FID) peaks at retention times of 3 min and 26 min, respectively. GC-EAD profiles of male headspace volatile extract indicated the presence of three distinct bioactive peaks elicited by both male and female antennae. These findings provided necessary leads for the identification of compounds in order to develop environmentally safe semiochemical-based control method for C. serratus.