Method for Use in Studies of Insect Chemical Communication

Abstract

INTEREST in the possibility of using behaviour-inducing chemicals to assist in the control of insect pests has stimulated efforts to isolate, identify and synthesize insect pheromones and food and oviposition attractants. Identification of these substances is usually difficult because of the low concentration of biologically active material in the insect or plant source. Usually fractionation of a crude extract followed by behavioural bioassay of each fraction is the procedure. Shortage of time and material often makes it difficult to give each fraction an adequate behavioural examination, especially if synergism is suspected. To overcome this difficulty we have developed a technique whereby all the olfactory stimulating compounds in an extract can be quickly detected. The method is based on the general assumption that the principal receptors used in insect olfactory communication are those on the antenna¹. It entails linking a gas chromatograph with the insect's antennal sense organs prepared for the recording of electroantennograms (EAGs). The volatile constituents of the test material are separated on the chromatographic column and the effluent is split between a flame ionization detector and the antenna. Simultaneous recording of gas chromatographic detector and insect responses makes possible the correlation of retention times with EAG responses.