Vapor-phase (S)-methoprene alters cuticular hydrocarbons in the Argentine ant (Hymenoptera: Formicidae)

The Argentine ant, Linepithema humile (Mayr), is one of the world’s most damaging invasive species. Current control strategies for L. humile rely on neurotoxic insecticides; however, their use is increasingly limited due to their environmental impacts and subsequent regulatory restrictions. Juvenile hormone analogues, such as methoprene, may offer an alternative solution due to their low toxicity to non-target organisms and more favorable environmental profiles. While some juvenile hormone analogues have been tested against several myrmicine ants, their effects on other subfamilies, such as Dolichoderinae, remain understudied. Only one peer-reviewed publication has evaluated methoprene’s effect on Argentine ant colonies in the laboratory, reporting increased mortality in adult workers. However, the study did not explore potential physiological mechanisms underlying this observation. Research findings from other insect taxa suggest that juvenile hormone and their synthetic analogues may disrupt adult physiology by altering lipid metabolism and cuticular hydrocarbon profiles, key traits involved in desiccation resistance and chemical communication. The current study investigated the effects of methoprene on the cuticular hydrocarbon profiles in L. humile. To administer methoprene in a controlled manner, small colony fractions housed in sealed enclosures were exposed to methoprene vapor. After 21 days, cuticular hydrocarbons were extracted from adult workers and queens and quantified using gas chromatography. Methoprene exposure significantly reduced the total cuticular hydrocarbon quantity in both castes. Moreover, the effect of methoprene on CHCs was dependent on their class and chain length, with caste-specific patterns. These findings suggest methoprene disrupts the lipid metabolic processes linked to cuticular hydrocarbon biosynthesis. These findings may provide a foundation to further explore the physiological impacts of methoprene and other juvenile hormone analogues on Argentine ants and other pestiferous dolichoderine ants.