Halofenozide affects sexual behaviour, cuticular hydrocarbons and reproduction in the female German cockroach Blattella germanica (Dictyoptera, Blattellidae)

Halofenozide, a dibenzoylhydrazine insect growth regulator, was applied topically to female individuals of the most prevalent German cockroach species, Blattella germanica, and its effects on sexual behaviour, cuticular hydrocarbons and reproduction were investigated. Dissection of treated females showed clearly reduced numbers of oocytes and volume of basal oocytes. Interestingly, the ecdysteroid amounts were also significantly lower. Characterization of the cuticular hydrocarbons by gas chromatography showed 13 major compounds, including the female contact sex pheromone precursor. It was clear that halofenozide application resulted in significantly lower amounts of all the investigated cuticular components. Finally, behavioural tests revealed that halofenozide treatment of females caused a significant decrease in sexual receptivity of the untreated conspecific males. Thus, exposure to the ecdysteroid agonist can negatively affect the male's response to a calling female, which is linked with and most likely caused by lesser production of female contact sex pheromone and a delay in the up-regulation of ecdysteroid amounts, and in turn this provoked an obvious lower oocyte number and basal oocyte size as measures of reproduction.