MALE LOAD-LIFTING CAPACITY AND MATING SUCCESS IN THE SWARMING CADDIS FLY ATHRIPSODES CINEREUS

Males of the caddis fly Athripsodes cinereus (Curtis) (Trichoptera: Le ptoceridae) swarm above the water surface of lakes and streams. Female s enter swarms and are pursued until grasped by a male. The pair coupl e their genitalia in the air, and then the male alone flies the pair t o the shore where they settle and complete the copulation. About 8% of the pairs (total n = 384 pairs) dipped in the water soon after the co upling manoeuvre and about 25% of those then separated. Males in dippi ng pairs (n = 13) were on average smaller and relatively older than th e males that successfully carried their mate to the shore (n = 54). No differences were found for flight muscle ratio (weight of flight musc les/total body weight) or relative load (total load/flight muscle weig ht). Males were larger than females (wing length), though typically fe male Trichoptera are the larger sex. Large male body size in A. cinere us may be an adaptation for flight during pairing; i.e. larger males a re more likely to be able to carry larger loads.