Parthenogenesis in mealybugs occurring on cocoa.
Three separate studies were conducted in 1992 and 1994-95 to investigate parthenogenesis in Planococcoides njalensis, Planococcus citri and Ferrisia virgata. In the first study, fecundity and survival of offspring were compared in laboratory-reared virgin females of P. njalensis and P. citri of different maternal origin, and between unmated and mated females of F. virgata. In the second study, fecundity and offspring survival were compared between unmated and mated females of P. njalensis and P. citri of different maternal origin over three generations. In the third study, fecundity and offspring survival of mated and unmated female P. citri siblings of female products of parthenogenesis were compared. Experiments one and three were replicated three times whilst experiment two was replicated ten times. In all three experiments, both mated and unmated females of the three mealybug species produced offspring, but fecundity was generally higher in the mated females. In one group of mated and unmated P. citri females, however, the unmated females produced offspring in the first generation, but not in the second generation, whilst their mated counterparts reproduced in all three generations. When mated and unmated female siblings of three females which were themselves reproduced by parthenogenesis were compared, all the ten unmated offspring of one of the females failed to reproduce. It was concluded that for the three mealybug species, reproduction is both sexual and parthenogenetic but that at some stage, yet to be determined, it becomes imperative for females produced by parthenogenesis to be mated for the continuation of subsequent generations.