Geographical variability in the photoperiodical reaction of the noctuid moth Euclidia gliphica (Linnaeus, 1758)

Abstract

Euclidia gliphica is the widespread Palearctic species. It has one generation, overwintering in the larval stage in Germany [Koch 1958]. Imago are recorded from May to July. Pyatigorsk and SaintPetersburg populations of this moth were investigated. During the experiment it was established that the winter pupal diapause in this species is not obligate, however the tendency to dormant state is very powerful. Under the temperature 24,4 °С and with the maximal day length 18 h, 80% of the pupi in Pyatigorsk population and 100% of the pupi in Saint-Petersburg population fell to the diapause. The investigation of the role of the daily temperature fluctuations (outdoors variants for both populations) revealed that the percentage of the diapausing insects was considerably lower: to 60% in the Pyatigorsk population and to 80% in the Saint-Petersburg population. Outdoors variants of the experiment was investigated from the beginning of July to the middle of August. In this period the day length was decreasing from 16 to 15.5 h. With this day length and constant temperature 24.4 °С the percentage of the diapausing insects in both populations was more than 90%. This explains the appearance of the active insects in first generation and, in turn, provides an opportunity for the second generation in these regions. It is possible, that in warm years, the number of active pupi can increase, but, according to the parameters of the photoperiodical reaction, a significant diapausing fraction will constantly present in the first generation

Keywords

• Euclidia gliphica
• pupal diapause
• photoperiod
• qualitative PhPR
• geographical variability of PhPR