JUVENILE-HORMONE PRODUCTION AND SEXUAL-MATURATION IN TRUE ARMYWORM, PSEUDALETIA-UNIPUNCTA (HAW) (LEPIDOPTERA, NOCTUIDAE) - A COMPARISON OF MIGRATORY AND NONMIGRATORY POPULATIONS

Previous work on North American populations of the true armyworm, Pseu daletia unipuncta, has shown that (1) ovarian development, pheromone s ynthesis, and the onset of calling (behavior associated with the emiss ion of the sex pheromone) in virgin females are positively correlated with an increase in juvenile hormone (JH) production, and (2) sexual m aturation is delayed under short-day, low-temperature conditions. Base d on these results and on the observation that this insect is unable t o survive the low temperatures of the Canadian winter, it has been hyp othesized that armyworm moths undertake seasonal north-south migration s in response to predictable habitat deterioration. Recently we obtain ed material from the Azores, a volcanic archipelago in the Atlantic Oc ean where the armyworm sustains populations all year round. We, theref ore, undertook a comparative study to test the hypothesis that the ear lier onset of calling behavior observed in this non-migrant population , relative to the North American population under identical conditions , was associated with an earlier induction of JH biosynthesis and a mo re rapid ovarian development. The results clearly supported this hypot hesis: JH biosynthesis increased at a significantly younger age in Azo rean females, although there were no differences in the relative propo rtions of the three JH homologues produced in vitro by CA of females s acrificed on their first night of calling. The early production of JH was reflected in a more rapid ovarian maturation although the data sug gest that sexual maturation in the Azorean population may require a lo wer JH titer. The importance of the observed differences are discussed with respect to the presence or absence of migration in each populati on. (C) 1996 Wiley-Liss, Inc.