Reproductive Maturity, Mating Status, and Long-Duration Flight Behavior of Agrotis ipsilon (Lepidoptera: Noctuidae) and the Conceptual Misuse of the Oogenesis'Flight Syndrome by Entomologists

The relationship between long-duration flight and the state of oogenesis in the migratory moth Agrotis ipsilon (Hufnagel) was examined in unmated females 1,2,3,4, and 5 d old by using computer-interfaced flight mills. Evidence presented suggests that such long-duration flights (i.e., continuous flights ≥1 h) are indices of migratory flight. There were no significant correlations between the number of chorionated eggs and flight duration, times of flight initiation and termination, or flight speed within age classes 1–4. In 5-d-old moths, however, there was a positive correlation with flight duration. Mated females began their long-duration flights ≍3 h later in the night and averaged 2 h of flight less than unmated females. Their propensity and capacity to engage in such flights, however, was still considerable. The long-duration flight behavior of 3-d-old mated males was similar to that of unmated males, as was their propensity to engage in such flights. Therefore, a delay in oogenesis and suppression of reproductive behavior are not prerequisites for the initiation of long-duration flight activity in A. ipsilon, as would be predicted if the oogenesis-flight syndrome was characteristic of this species. Our data are consistent with previous findings that suggest that most females arrive in the midwestern United States in the spring already mated. We argue that the concept of an oogenesis-flight syndrome in migratory insects has no inherent explanatory power and its only valid use is as a convenient descriptive term. Its most frequent misuse as an explanatory principle is seen in the common assumption that duration of the prereproductive period determines the maximum duration of the migratory period. Empirical evidence as well as theoretical considerations indicate that it is never safe to accept this assumption without testing. To do so risks impeding progress in understanding specific systems through unwarranted extrapolation of data or through building a house of cards.