Eighty species of Psocoptera, of 15 families, were collected on the four Krakatau islands in 1982—86, about a century after the 1883 eruption of Krakatau. The most abundant species on the Krakataus (in the families Lepidopsocidae, Ectopsocidae and Peripsocidae, which are also three of the four most diverse families on the Krakatau group) are typical early colonizing forms, but several ecologically more specialized taxa are also present, and some are limited to particular kinds of vegetation. Families characteristic of forest habitats, Pseudocaeciliidae, Myopsocidae and Psocidae, are poorly represented on the Krakataus. The faunas of Rakata and Panjang are markedly more diverse than those known for Sertung or Anak Krakatau, and the first pair of islands, the only one of the six possible pairs to consist wholly of mixed secondary forest, show the greatest faunal similarity. By reference to the presumed source faunas, there is evidence that the most diverse family on the Krakataus, Caeciliidae, (18 species present) is typical of the order as a whole in colonizing ability, whereas the Lepidopsocidae (11), Ectopsocidae (13) and Peripsocidae (11) are relatively good colonizers, and the Pseudocaeciliidae (3), Myopsocidae (2) and Psocidae (4) relatively poor ones. Within the archipelago, the same trends are apparent for the colonization of the young island of Anak Krakatau, which emerged from the sea in 1930. Taking the three other Krakatau islands as the source, the Caeciliidae again show average colonizing ability, and Lepidopsocidae and Ectopsocidae again are relatively good colonizers. The Peripsocidae, however, show up as rather poorer ones in this model. Because species of this family are predominantly bark dwellers their habitat would not be available as early as that for species of the other families, which are found largely on leaf litter and on living leaves. Progressive development of the psocopteran fauna of the archipelago is discussed in relation to vegetational succession.