Production of sexual and asexual morphs and changes in reproductive sequence associated with photoperiod in the pea aphid, Acyrthosiphon pisum (Harris)

Abstract

Production of sexual and asexual morphs of a clone of the pea aphid, Acyrthosiphon pisum (Harris), was monitored under photoperiods ranging from 18L:6D to 10L:14D at 20 °C. Under long photophases only viviparae were produced. At intermediate photophases families were produced in which the oldest progeny were females while the youngest progeny were males. A 1- to 2-day pause intervened between the production of these two groups. Females were produced only for 3–4 days while males were produced for about 12 days. At longer intermediate photophases the females were viviparae while at shorter intermediate photophases they were oviparae. In families containing both female morphs, viviparae were born first. At the shortest photophases, families consisted entirely of females, oviparae being produced in the first half and viviparae in the second half of the reproductive period. The ecological significance of these sequences is discussed.