Electrophysiological and behavioural responses of Melolontha melolontha to saturated and unsaturated aliphatic alcohols

Abstract

Male Melolontha cockchafers are known to use green leaf volatiles induced by female feeding on host plants for their mate location. Earlier studies of the response of the European cockchafer, Melolontha melolontha L. (Coleoptera: Scarabaeidae), to different green leaf aldehydes, alcohols, and acetates revealed that only green leaf alcohols were attractive to males in the field. Females were not attracted at all by these volatiles. Here, we present a study that aimed to elucidate the structure–activity relationships of aliphatic alcohols. Both behavioural and physiological responses were studied in male and female M. melolontha by field tests and electroantennography. The compounds tested were saturated aliphatic alcohols with chain lengths between five and eight carbon atoms. Furthermore, the cockchafer's response to six-carbon alcohols with (E)-2-, (E)-3-, (Z)-2-, (Z)-3-, and (Z)-4-configurated double bonds was tested. All compounds elicited dose-dependent responses on the antennae of both sexes. In general, males showed a stronger normalized EAG response to the stimuli than females. However, only the naturally occurring six-carbon alcohols, i.e., 1-hexanol (E)-2-, (Z)-3, and (E)-3-hexen-1-ol were attractive to M. melolontha males in the field. Females were not attracted to any of the tested compounds, confirming previous results on the olfactory orientation of Melolontha cockchafers.