4.2
FLIGHT ENERGETICS AND OPTIMIZATION STRATEGIES FOR LONG-DISTANCE INSECT MIGRANTS

Robert Dudley, Univ. of Texas, Austin, TX


The energetic costs of flight influence insect migration strategies for wind-assisted dispersal as well as for intentionally directed displacement within the flight boundary layer. Small insects being convectively dispersed must nonetheless maintain a forward airspeed and offset their body weight during flight, or alternatively must reduce their flight velocity so as to hover within a moving air volume. If the goal of dispersal is to maximize the horizontal distance travelled, then flight at the minimum power speed would maximize time aloft and thus the magnitude of wind-assisted displacement. By contrast, migration within the flight boundary layer likely occurs at the maximum range speed that optimizes horizontal coverage using powered flapping flight alone. No data are presently available that assess insect airspeeds (as distinct from groundspeeds) and associated rates of energetic expenditure during predominantly convective dispersal. Moreover, aerodynamic models that predict optimal airspeeds are seriously compromised if energy stores can be replenished during migration. For boundary layer migrants in particular, the fixed availability of endogenous reserves may be substantially augmented through nectar feeding or related strategies during long-distance flights. In such cases, the optimal flight speed for maximum migratory distance may vary substantially according to the instantaneous mass and energy balance. A diversity of energetic strategies may thus characterize both boundary layer migrants as well as predominantly wind-assisted migratory forms.

The 13th Conference on Biometeorology and Aerobiology