Buoyancy and diving behavior in mosquito pupae

Mosquito pupal diving behavior has been studied mostly in Aedes aegypti and in this species pupal buoyancy varies relative to several factors. The res earch reported herein addresses the 3 following questions. Does diving beha vior vary among different mosquito genera and species? I-few is diving beha vior influenced by variation in buoyancy? Depth and duration of dive, and d ive pattern, were compared among Ae. aegypti, Culex pipiens, Anopheles step hensi, Aedes albopictus, and Aedes triseriatus, In response to the stimulat ion associated with transferring pupae between containers, diving behavior varied dramatically among the different genera studied. Culex pipiens and A n. stephensi make short-duration, shallow dives and remain positively buoya nt. The 3 aedine species studied make longer-duration dives, typically to a depth at which they become neutrally or negatively buoyant. Buoyancy reduc tion effects were studied in the 3 aedine species. Normally buoyant pupae t end to dive to greater depths and for longer periods of time than reduced-b uoyancy pupae, Aedine pupal diving behavior clearly is closely regulated re lative to buoyancy variation. To the earlier hypotheses that pupal behavior may help avoid predation and be energy-conserving, we add the suggestion t hat the diving behavior displayed by the container-breeding aedine pupae we studied represents an adaptation that helps keep them from being washed fr om their container habitat by overflowing water during rainfall. We also su ggest that the diving behavior of all the species studied may help pupae su rvive heavy, pelting rainfall by enabling them to avoid the mechanical shoc k of a direct hit by a raindrop. which could cause disruption of the gas in the ventral air space, thereby causing the loss of hydrostatic balance and drowning.