Periodicity in Mate Attraction and Flight Activity of Three Species of Caddisflies (Trichoptera)

Abstract

Diel periodicities of mate attraction and flight activity were examined for three caddisfly species (Insecta:Trichoptera) that use female sex pheromones to attract conspecific males: Dicosmoecus gilvipes (Hagen) (Limnephilidae), Gumaga nigricula (McL.) (Sericostomatidae), and Gumaga griseola (McL.). Live females of D. gilvipes attracted males during the night, with 58% of the males being captured in the first hour after sunset. Live females of G. griseola attracted 97% of the males during the hour before sunrise whereas live females of G. nigricula attracted 85% of the males 2-4 h after sunrise. For all three species, the periodicity of male response to female pheromone was the same as the periodicity of male response to live females. In laboratory chambers, male and female D. gilvipes flew during the mate attraction period but generally not at other times. Male flight for G. nigricula and G. griseola was generally most intense during periods of mate attraction, and was reduced during non-attraction periods. In contrast, females of both Gumaga species were relatively sedentary during periods of mate attraction. The presence of circadian rhythms that govern the periodicity of flight was demonstrated for all taxa and sexes except females of D. gilvipes. Light intensity and air temperature influenced the amount of flight activity but not flight periodicity. The temporally brief and coordinated activities of these short-lived adults may serve to conserve metabolic resources, contribute to their reproductive success, and maintain reproductive isolation.