The trail-following communication in Stylotermes spp. (Blattodea, Isoptera, Stylotermitidae)

Abstract

Stylotermitidae appear peculiar among all termites, feeding in trunks of living trees in South Asia only. The difficulty to collect them limits our ability to study them, and they thus still belong to critically unknown groups in respect to their biology. We used a combined approach of microscopic observations, chemical analysis and behavioural tests, to understand the source and chemical nature of the trail-following pheromone of Stylotermes faveolus from India and S. halumicus from Taiwan. The sternal gland is the exclusive source of the trail-following pheromone in both Stylotermes species. It is located at the 5th abdominal sternite in workers, made of class I, II and III secretory cells. Gas chromatography coupled to mass spectrometry showed a minor peak corresponding to (Z)-dodec-3-en-1-ol (DOE). This compound elicits strong behavioural responses in workers, with a trail-following activity threshold around 10− 4 ng/cm in both species. Based on both chemical analysis and behavioural experiments, we estimated the amount of DOE around 0.1 ng/gland in S. faveolus and we conclude that DOE is the only active component of the trail-following pheromone of both Stylotermes species, like in all Kalotermitidae studied so far. Our results confirm the switch from complex aldehyde trail-following pheromones occurring in the basal groups to simpler linear alcohols in the ancestor of Kalotermitidae and Neoisoptera.