Who are the littluns in Lord of the Flies?

In Lord of the Flies, the Littleuns are the young boys who tend to be six or seven years old.  These little boys are characterized by being irresponsible, dirty, ravenous, but still more mature than you would expect for six and seven year olds.  Piggy stresses that they don't know how to take care of themselves as they eat any bit of fruit they find, relieve themselves anywhere they feel like, sleep, play, and do little constructive to help the rest of the boys.  The most notable little boy was the one who was left nameless with the large birthmark on his face.  He was the one who was killed early on in the fire and had announced the fear of the beastie.  Otherwise, there are a variety of other littluns on the island.