Phonotaxis to Amphibian Vocalizations in Culex territans (Diptera: Culicidae)

Culex territans Walker (Diptera: Culicidae) acquires bloodmeals from amphibian hosts. Females overwinter as inseminated adults and exit diapause in New Jersey when spring peepers (Pseudacris crucifer) are calling. We tested the hypothesis that Cx. territans uses amphibian vocalizations as a long-distance attractant. Two thirds of females oriented toward sound across all experiments. Females allowed to orient toward or away from a frog call, bird song, live frog, or control (a plugged in compact disc player) exhibited positive phonotaxis only to the frog call. Females exhibited positive phonotaxis to calls of P. crucifer, Hyla versicolor (northern gray tree frog), Bufo americanus (American toad), and Rana clamitans (green frog), but they were not attracted to calls of R. catesbeiana (bullfrog), R. sylvatica (wood frog), or control. Multiple regression analysis showed that call frequency is the best predictor for phonotaxis, with pulse duration and call amplitude increasing the attractiveness of the source. When exposed to P. crucifer calls at increasing sound intensity levels, females oriented to calls in the range of 50–75 dB, with particle velocities of 0.02–0.3 mm/s, indicating that phonotaxis occurs at distances >5 m from the source.