LIPID AND CARBOHYDRATE UTILIZATION DURING FLIGHT OF THE MIGRATORY MOTH, AGROTIS-IPSILON (LEPIDOPTERA, NOCTUIDAE)

Male black cutworm, Agrotis ipsilon (Hufnagel) moths, were attached to laboratory flight mills on the third night after emergence. Individua ls were classified according to their longest uninterrupted flight dur ing the night. There were not enough non-fliers or trivial fliers (fli ght < 1 h) to make meaningful comparisons, so only short-fliers (fligh t greater than or equal to 1 h but less than or equal to 5 h) and long -fliers (flights greater than or equal to 5 h) were further tested. Af ter a day of rest, short- and long-fliers were tethered to a stationar y pin and forced to fly 0, 10, 20, 30, 60, 120, or 180 min, after whic h hemolymph was sampled and lipid and carbohydrate concentrations dete rmined. Concentrations in samples taken at intervals after cessation o f a 60-min flight indicated that both energy sources were being utiliz ed during flight. Neck-ligation experiments indicated that a handling- induced hyperlipemic response occurs 15 min after the beginning of the sampling procedure, and that the hormone triggering does not come fro m the head. Resting concentration of lipid in long-fliers is about hal f that of short-fliers, but it increases threefold in the first 20 min of flight, whereas that of short-fliers remains unchanged. In-flight lipid concentration in controls, which experienced their first and onl y flight on day 5, was greater than the concentration in both short- a nd long-fliers. Between 10 and 20 min, carbohydrate concentrations dec rease about twofold in long-fliers but drop only slightly in short-fli ers. These data suggest that long-fliers may have a lower basal metabo lic rate and depend more on carbohydrate when at rest than short-flier s, and that long-fliers may utilize more carbohydrate than lipid durin g the initial period of flight. In addition, previous flight on the fl ight mills has a greater influence on lipid mobilization and usage in short-fliers than it does on long-fliers. Patterns of lipid mobilizati on during flight seem to differ between migrant and non-migrant specie s and to vary among migrants depending on the fight strategy used, but there are no major differences in patterns of carbohydrate usage. (C) 1995 Wiley-Liss, Inc.