Cannibalism of eggs by larvae ofAdalia bipunctata, an aphidophagous species of ladybirds, is important for survival when aphids are scarce. Ladybirds survive longer by eating eggs of their own species rather than aphids. Since it costs less, in terms of larval growth, to eat eggs rather than aphids, cannibalism has a strong advantage under conditions of prey scarcity.
The mustard aphid,Lipaphis erysimi (Kaltenbach) is a serious pest of mustard in India and other tropical regions in the world. The population dynamics of this species is considerably influenced by immigrant alatae which migrate to the mustard crop from the off-season shelter. Aphids reproduce at a higher rate in the early vegetative stage of mustard plants when the developmental period is shortest and production of winged morphs is lowest. The population reaches an asymptote when the crop is 70 days old. The species regulates its developmental period, fecundity and intrinsic rate of increase in response to developmental changes of the mustard plant and maintains its dispersal throughout the duration of the mustard crop. In succeeding generations on a mustard plant new born nymphs took increasingly longer to develop into adults and over the same period these adults produced decreasingly fewer numbers of offspring. In the inflorescence and fruiting stages of mustard plants a higher proportion of the nymphs developed into alatae.