Anatomical locations of the photoreceptor and circadian pacemaker for the locomotor activity rhythm were investigated by removal of the external photoreceptors, the compound eyes and ocelli, or the optic lobes in the adult cricket, Dianemobius nigrofasciatus (Orthoptera: Gryllidae). The activity rhythm of intact crickets freeran under DD with a freerunning period (τ) of 24.6 ± 1.0 h (mean ± SD) and entrained to light-dark cycles of LD 13:13 and LD 12:12. When both compound eyes were removed, some crickets entrained both to LD 13:13 and LD 12:12. Some of the others entrained only to LD 12:12 or showed a complex pattern of the activity. When both compound eyes and all ocelli were removed, some crickets still entrained both to LD 13:13 and LD 12:12. The activity pattern of the crickets receiving a sham operation or unilateral removal of the compound eye was not different from that in the intact crickets. Bilateral removal of the optic lobes caused arrhythmicity both under LD 13:13 and DD, although the activity rhythm in crickets of which the optic lobe was unilaterally removed entrained to LD 13:13 and freeran under DD. These results suggest that D. nigrofasciatus possesses its circadian pacemaker in the optic lobe, and uses both extraretinal photoreceptors and compound eyes for its entrainment.