The Influence of Environment and Heredity on Flight Activity in the Milkweed Bug Oncopeltus

Abstract

1. Most long flights of Oncopeltus, tested using tethered flight in the laboratory, took place during the middle of the day. This is consistent with field data from other Heteroptera. 2. In bugs reared at 23° C., regardless of length of photoperiod, 20% of males and 30% of females were migrants. Temperatures of 19° and 27° C. reduced these proportions. 3. A short photoperiod of 12 hr. of light failed to increase the proportion of migrants over that present at 16 hr. The period in the life-history during which migration took place, however, was lengthened considerably. In spite of the lengthened flight period and a delay in oviposition, migrants arrive at their destinations with reproductive value high and are therefore colonizers. 4. Food deprivation may increase somewhat the proportion of migrants if it occurs shortly after eclosion, although most of the extra activity seems to be due to additional non-migratory flight. If it occurs after oviposition has begun, food deprivation can result in migration at a time when it would ordinarily have ceased. 5. The proportion of migrants could be significantly increased by appropriate selection and breeding. The basis for migratory behaviour is thus, in part at least, genetic. 6. The data in general support the hypothesis that migration is elicited, enhanced, or suppressed in genotypical migrants by those environmental factors which influence ovary (and corpus allatum) development.