Summary Apterous parthenogentic females of the pea aphid, Acyrthosiphon pisum (Harris), begin to produce alate offspring soon after they have been subjected to crowding. Females which were born early in their own parent's reproductive period respond most strongly to crowding, producing much larger numbers of alatae than their late‐born sisters. In contrast, the early‐born daughters of most alate females do not produce winged offspring after being crowded. Some of their later‐born sisters may produce a few winged individuals, resembling in this respect the late‐born daughters of the apterous females. Control of the production of alatae thus begins in the grandparental generation. Risk‐spreading by means of differential dispersal becomes a less uncertain venture when local populations can modify their responses to environmental changes by utilizing past as well as present signals from their surroundings.

The main component of mammalian maternal care is milk production. The composition of milk has been hypothesized to determine offspring survival, and to vary with offspring sex. Few studies, however, have examined variation in milk composition of wild mammals in seasonal environments, where environmental conditions can impact the ability of mothers to provide care. We investigated individual differences in milk composition and offspring survival in wild eastern grey kangaroos (Macropus giganteus). We analyzed total protein and lipid concentrations in 103 milk samples from 91 females over 2 years. In a year of low forage production, few females that lactated were in poorer condition and produced milk of lower energy content compared to females lactating in a year of high forage production. Females nursing in late winter produced milk with more lipids compared to females at the same stage of lactation in late spring, whose milk had a higher proportion of protein. The milk of larger females contained more protein than lipid, and females in better condition allocated higher proportions of protein to sons than to daughters. Increased protein concentration in milk was correlated with offspring longevity, and this effect was stronger for sons than daughters. A seasonally modulated lactation strategy enables the adjustment of milk composition to available resources. Condition‐specific protein allocation in favor of sons for mothers of higher caring ability suggests adaptive sex‐biased maternal care in this highly sexually dimorphic mammal.

No abstract