PHENOLOGY AND LIFE-CYCLE REGULATION OF THE FISHING SPIDER DOLOMEDES TRITON WALCKENAER (ARANEAE, PISAURIDAE) IN CENTRAL ALBERTA

Dolomedes triton Walckenaer, a widespread and common fishing spider in North America, has a semivoltine life cycle in central Alberta, Canad a. Juvenile spiders hibernate twice. According to evidence from labora tory rearings and patterns in field collections, the main overwinterin g stages are instars 3-5 and 9-11. After the second overwintering peri od, large juveniles moult once or twice to reach the reproductive adul t stage. Juveniles grow rapidly between May and August but during over wintering between September and April, virtually no growth (measured a s maximum carapace width of individuals) was observed in field populat ions. Dolomedes triton has a variable number of juvenile stages, rangi ng from 10 to 15 in males and from 9 to 15 in females. Both overwinter ing phases are facultative even though most individuals overwinter twi ce in central Alberta: at high temperatures (24-25 degrees C) and unde r long-day conditions (either 18 h light : 6 h dark or 19 h light : 5 h dark) juveniles can develop directly to adults. Short-day photoperio ds did not prolong stage durations, bur warm periods, when experienced late in development only, were associated with extra moults, and may thus delay maturation until the following spring. Although the second overwintering period is a quiescence regulated strictly by temperature , regulation of the first overwintering period is more complex, includ ing probable preconditioning through interaction of temperature and ph otoperiod.