Simulium vittatum (Simuliidae: Diptera), a black fly with a variable instar number

Abstract

Simulium vittatum is a black fly that normally has 7 larval instars but may undergo several more, with a maximum of 11 instars being recorded in this study. The size increase was relatively constant between individuals for any one instar under similar conditions, but the increase in the first two molts was much greater than observed between late instars. There was little relationship between the relative sizes of certain head capsule measurements in the final instar, indicating the difficulty in determining stable characters for taxonomic separation of closely related simuliid species.