Flight initiation as a sex and context dependent trait shaped by physiological state in Triatoma infestans

Dispersal of Triatoma infestans, a major vector of Chagas disease, is a key process shaping its spatial dynamics. In the Gran Chaco, where the species persists despite long-term control efforts, understanding the determinants of flight initiation is essential to uncover the mechanisms underlying dispersal. We conducted two laboratory flight initiation assays under contrasting nutritional conditions (starved and fed). Flight behavior was recorded with infrared video, and we quantified nutritional status, flight muscle ratio, and female reproductive parameters. Linear and geometric morphometrics of wings and heads assessed size and shape variation. Flight initiation differed by sex and context. Under starvation, females initiated flight more frequently than males, whereas feeding reduced initiation in both sexes. In males, flight initiation was positively associated with flight muscle ratio; while no physiological predictors were clearly associated with flight initiation in females. Morphometrical shape variation was not associated with flight initiation, although flying females tended to have larger wings and heads. Overall, flight initiation in T. infestans is sex- and context-dependent and primarily driven by physiological condition rather than fixed morphology, providing a mechanistic basis relevant to models of dispersal and reinfestation and to regional vector surveillance and control strategies.