Hormonal control of migratory flight in Oncopeltus fasciatus: The effects of the corpus cardiacum, corpus allatum, and starvation on migration and reproduction

Abstract

The effects of starvation on the activity of the corpus allatum (CA) and on migratory flight behavior and as the effect of the corpus cardiacum (CC) on migratory behavior were examined. Juvenile hormone (JH) titer determinations were done on Oncopeltus hemolymph using the Manduca pigmentation bioassay. Starvation resulted in a decrease in measureable JH in Oncopeltus hemolymph over a period of 5–6 days after which time JH titers were undetectable. Flight behavior increased for the first 4–6 days after the beginning of starvation, then decreased to very low levels as JH titers diminished. Topical applications of the JH mimic ZR512 to starved individuals 9 days after starvation restored flight to its former high level. However, implantation of three CC into starved Oncopeltus at this time had no effect on flight. Oviposition was also inhibited by starvation. Feeding Oncopeltus on suboptimal food (green pods) resulted in a significant delay in reproduction and an increase in flight activity similar to that seen in diapausing individuals. Therefore, JH is the primary hormone responsible for the stimulation and coordination of migration and reproduction while the CC appears not to be involved in the stimulation of migratory behavior in this species. Food shortage or suboptimal food appears to be important in initiating the spring migratory flight by maintaining the hemolymph JH titers at a level below the threshold for ovarian development but above that necessary to stimulate migratory flight.