Methoprene influences reproduction and flight capacity in adults of the rice leaf roller, Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae).

ABSTRACT

Juvenile hormone (JH) influences many aspects of insect biology, including oogenesis-flight syndrome tradeoffs between migration and reproduction. Drawing on studies of many migratory insects, we posed the hypothesis that JH influences migratory capacity and oogenesis in the rice leaf roller, Cnaphalocrocis medinalis. We treated adults moths (days 1, 2 and 3 postemergence) with the JH analog (JHA), methoprene, and then recorded the influences of JHA treatments on reproduction. JHA treatment on day 1 postemergence, but not on the other days, shortened the preoviposition period, although JHA did not influence total fecundity, oviposition period, or longevity. We infer day 1 postemergence is the JH-sensitive stage to influence reproduction. Therefore, we treated moths on day 1 postemergence with JHA and recorded flight capacity, flight muscle mass, and triacylglycerol (TAG) accumulation. JHA treatments did not influence flight speed, but led to reductions in flight durations and flight distances. At day 3 posttreatment (PT), JHA-treated females flew shorter times and less distance than the controls; JHA-treated males, however, only flew shorter times than the controls. JHA treatments led to reductions in flight muscle mass in females at days 2-3 PT and reductions in TAG content in females at day 3 PT, but, these parameters were not influenced by JHA in males. These findings strongly support our hypothesis, from which we infer that JH is a major driver in C. medinalis oogenesis-flight syndrome tradeoffs. Our data also reveal a JH-sensitive stage in adulthood during which JH influences the oocyte-flight syndrome in C. medinalis.