The variation during development in the following characters of Lithobius microps is described: body-length, head-length, ratio head-length/body-length and head-length/ head-width, number of coxal pores, ocelli, antennal articles and teeth on forcipular coxosternite, projections on tergites 9, 11 and 13, spinulation on the last pair of legs, accessory apical claws on the 15th pair of legs, genitalia and the pattern on the cephalic shield. Also the difference between male and female and the correlation with size within each post-larval stadium are given. The boundary between juvenile and adult stadia, the number of post-larval stadia and the geographical variation in the number of antennal articles and coxal pores are discussed.