Decanal as a major component of larval aggregation pheromone of the greater wax moth, Galleria mellonella

Larvae of the greater wax moth (GWM), Galleria mellonella, a destructive pest of the honeybee (Apis mellifera), have been observed to display aggregation behaviours. However, the underlying mechanism by which these larvae come together remains unknown. We hypothesized that the GWM larvae detect, orient towards and utilize conspecific larval chemical cues to aggregate in groups. We used dual-choice olfactometer assays to investigate the involvement of conspecific larval odours in their aggregation amongst 3-5th instar and 8th instar larvae. The assays revealed that only 8th instar larvae were significantly attracted to their odours and those emanating from newly spun cocoons. Coupled gas chromatography-mass spectrometry (GC-MS) of larval head space odours analysis revealed the presence of four compounds: nonanal, decanal, tridecane and tetradecane in pupal and mature larval odour extracts. However, using synthetic compounds, behavioural assays showed that only decanal induced significant attraction, therefore, suggesting its role as a major component of the larval aggregation pheromone of GWM. Our findings reveal the involvement of volatile organic compounds in the aggregation behaviour of mature wax moth larvae and thereby offer prospects for the development of an odour-baited in-hive trapping management tool for wax moth larva.