Interspecific and intraspecific selection by the predator Notiophilus biguttatus F. (Carabidae) concerning two collembolan prey species

Summary

Observations on predation by the diurnally active predator Notiophilus biguttatus F., show that locomotory activity of the prey favours capture. Of the two prey species studied, Orchesella cincta and Tomocerus minor, the former is by far the most active one during the day. Since the moulting rhythm causes only part of a group of O. cincta to be active, predation towards this species is selective: active specimens are “preferred”. Tomocerus minor is almost inactive during the day (but may be activated by disturbance from the predator), which inhibits such a selection. Orchesella cincta also shows, when attacked, a greater escape ability than T. minor. So, inactive O. cincta are captured less easily than T. minor. Thus, locomotory activity and escape ability both cause a variable preference of the predator. When a sufficiently high number of active O. cincta specimens is present, this species will be preferred; when the number of active O. cincta specimens is low, e.g. as a consequence of predation, T. minor might be preferred.