Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Cuticular hydrocarbons C14-C36 are potential contact pheromonal elements modulating some behaviors in Zygogramma bicolorata (Coleoptera: Chrysomelidae).

Abstract

Chrysomelid beetle, Zygogramma bicolorata (Pallister, 1953) (Coleoptera: Chrysomelidae), is an important biocontrol agent for the weed Parthenium hysterophorus. The insect spends its whole life on the same plant, which acts as an essential site for feeding, mating and oviposition. These insects were studied for repeated mating, either to same or different mates, and the results indicated both polyandrous and polygamous mating with same-pair mating preferences. Apart from this, a preliminary bioassay was performed individually for both the sexes to detect the presence of contact pheromones. These chemicals, ranging from C14 to C36 and often known as cuticular hydrocarbons (straight and branched), were further identified by reading their mass spectra. Although the hydrocarbon profiles of males and females resembled each other qualitatively, the compounds showed a significant difference with respect to their relative proportions. The antennal response to some of the corresponding synthetic straight chain alkanes (Pentacosane, Hexatriacontane, Docosane, Tetracosane, Heneicosane, Hexacosane, Octadecane, Eicosane and Tetratriacontane) were also tested using electroantennography (EAG) at four different concentrations (0.1%, 0.01%, 0.001% and 0.0001%). The mean EAG response obtained was observed to be sex dependent for all compounds tested. The antennae of female responded strongly to these compounds with Tetratriacontane eliciting the highest response of - 0.684 mV at the concentration 0.01%. The difference in the responses may be attributed to the differences in the release rates of these compounds and the sensitivity of antennal responses between the sexes.