Electronic fraction collector used for insect sampling in the photoperiod-induced diel emergence of bark beetles

ABSTRACT. An electronic timer and fraction collector consisting of CMOS integrated circuits is described. It converts 50- or 60-Hz AC to real-time pulses in programmable whole-number increments (1, 10 or 60s) from 3 to 16659, producing timing periods from 3 s to more than 11 days. The fraction collector contains a leaf-switch feedback circuit that automatically adjusts to various gear motor speeds and sample tube spacings so that proper positioning results. Hourly collections by the device of the bark beetles Ips typographus L. and Pityogenes chalcographus L. (Scolytidae) emerging from logs of Norway spruce, Picea abies , indicated that both species emerged with a diel periodicity. A unimodal emergence peak for both sexes of both species occurred at midday in LD 20:4 at a constant 25°C and 80% r.h.