In Chapter 4, the narrator of The Lord of the Flies explains that the littleuns have learned to adapt to their new situation: "They ate most of the day, picking fruit where they could reach it and not particular about ripeness and quality. They were used now to stomach-aches and a sort of chronic diarrhoea."
The fact that the youngest boys have grown accustomed to a constant discomfort as a result of their eating habits represents their general ability to adapt to life without grownups. They now can choose what they eat, rather than have meals prepared for them, and they live with the consequences of both good and bad food choices. This resilience is both a positive sign and a troubling one: many of the youngsters are indeed very resilient, as they cry less for their mothers than the narrator expects and they live as a group without bothering the older boys much, but the difficulty lies in their inability to take good enough care of themselves, which leads to illness and pain, and an appalling absence of good hygiene that endangers them and others.