The bagworm Oiketicus kirbyi (Lands.-Guilding), an extremely polyphagous insect, is a pest of several crops of economic importance mainly in the southern region on Brazil. It occurs in eucalipt plantations although no outbreaks have been registered until today. This paper deals with the biology of 0. kirbyi on Eucalyptus spp. leaves. The insect was reared in laboratory conditions (temperature of 25±3°C, relative humidity of 70±10%, and photophase of 13 hours) and the following mean values were obtained: egg period of 43.1 days; larval period of 140 days (males) and 151 days (females); pupal period of 38.2 days (males); adult longevity of 3.0 days (males) and 3.9 days (females), and oviposition period of 2.1 days. Other data obtained were: dimensions of egg, pupa, adult and head capsules; number of larval instars; mating period and estimation of leaf damage.