Pit-fall trapping in fell-field habitat at about I00 m a.s. on the sub-antarctic Possession Island, Crozet Islands, showed that surface activity in Amblystogenium minimum Luff (Carabidae) fell suddenly to low levels after mating was largely completed in mid-February. In A. pacificum (Putzeys) also a fall in activity occurred at the same time but this species continued limited activity into late autumn. Both species are autumn breeders, with the last named continuing some egg maturation into the winter. A. minimum of smaller body size had ripe oocytes of smaller mean length than the larger A. pacificum which occurred as brown and black coloured adults. Collecting-out of areas of known size when the two species co-existed gave the following density estimates /m2: on stone and gravel ground about 0.7, and on rock pavement of 2.3 of each species. Comparison of pit-fall trapped samples with that of hand collected material suggest that A. minimum showed no differences between the sexes in overall activity, while in A. pacificum males were more active than females. The latter, larger species was more active than the smaller A. minimum. Limited larval material together with the occurrence of teneral adults in low numbers in February-April suggest an unsynchronized larval life lasting a year or more, and unsynchronized emergence in late summer and autumn of adults that do not breed until the following late summer, so that the total life cycle takes two years or more.