Investment in gynoparae and males by Myzus persicae (Sulzer)

Investigated the effect of manipulating an environmental cue (day length) on the timing of sexual offspring production and the relative investment in Myzus persicae males and gynoparae. The latter are winged parthenogenetic females capable of giving birth to sexual female offspring (oviparae). Exposure of wingless parthenogenetic females to long nights brings about endocrine changes resulting in the production of gynoparae and males on the summer (secondary) host plant. Gynoparae and males then fly to the winter (primary) host, whereas the oviparae are born, mating occurs and overwintering eggs are laid. Gynoparae precede males among the progeny of an individual. The sex ratio on the secondary host is male biased. Because each gynopara contains 4-5 oviparae, the ultimate sex ratio on the primary host is potentially slightly female biased. The field sex ratio, however, will depend on survival time of the mothers of the sexual forms, those that survive longer producing relatively more males. -from Authors