Vestigial photoperiodic response in subarctic Myrmica ants

Studies carried out on the effects of day-length on the development of the arctic insects are probably less because the Polar day does not provide str ong photoperiodic cues. In arthropods living in the subarctic zone, where p hotoperiodic signals are relatively more distinct, the role of day-length i n the control of seasonal life cycles has been studied only by a few worker s. We performed experiments on two species of Myrmica ants from two populat ions in the Polar Circle region, which revealed a clear-cut photoperiodic r esponse that appeared to be 'vestigial', i.e. nonadaptive and unfit to indu ce diapause in proper time under natural photoperiodic conditions.