A population comprisingCelatoblatta peninsularisandParellipsidion pachycercumwas sampled from Banks Peninsula, New Zealand over 1 year. Sub-adult cockroaches were assigned to 6 size classes (probably instars) by interocular distance and hind femur length.P. pachycercumwas most abundant in December and January and adults were abundant in most months. In contrast,C. peninsulariswas most abundant from February to June and adults were rare except in November. Adult females were less abundant than adult males in both species. Although both species may be bivoltine, they use difference overwintering strategies.