Meeting Abstract
Dispersal flight is an important component of life history strategies for many animals. For insects, the only ectotherms to have evolved powered flight, dispersal at night may present a challenge because low temperatures can limit physiological functions. Gryllus lineaticeps crickets have a wing polymorphism consisting of flight-capable (long wing; LW) and -incapable (short wing, SW) morphs. In the field, temperatures during the active period are frequently below the threshold for flight initiation. We test four non-exclusive hypotheses to determine the strategies nocturnal insects use to achieve flight: 1) behavioral thermoregulation to increase Tb; 2) pre-flight warm-up using muscular contractions; 3) resistance to heat loss; 4) modification of thermal performance curves to permit flight at low body temperature. Experiments on wild and lab-reared crickets showed that LW crickets had higher thermal preferences and field body temperatures than SW crickets. They performed wing-shaking prior to flight initiation, which further raised their body temperatures until they reached the threshold temperature for flight initiation. LW crickets had higher mass-specific metabolic rates and a greater resistance to passive cooling compared to SW crickets. Thus, we found support for all four hypotheses and conclude that LW crickets use a combination of behavioral and physiological strategies to facilitate nocturnal flight. Our study highlights the complexity and diversity of responses to variable thermal environments in ectotherms.
