SURVIVAL AND DEVELOPMENT OF IXODES-SCAPULARIS (ACARI, IXODIDAE) UNDERVARIOUS CLIMATIC CONDITIONS IN ONTARIO, CANADA

Distribution of the blacklegged tick, Ixodes scapularis Say, is poorly defined in Ontario. An endemic population is known on Long Point peni nsula, Lake Erie, Ontario, but I. scapularis adults have also been col lected from other localities within the province. To test the hypothes is that distribution of the blacklegged tick is limited by cold climat ic extremes, 35 fed female, 70 unfed adult, and 70 unfed nymphal I. sc apularis were held in containers within four natural habitats on Long Point (42 degrees 36' N; 80 degrees 5' W) and at northern localities n ear Ottawa (45 degrees 27' N; 75 degrees 42' W), Hearst (49 degrees 40 ' N; 83 degrees 41' W), and Kenora (49 degrees 47' N; 94 degrees 29' W ), Ontario, from early December 1991 until May 1993, At the northern l ocalities 84.8 and 30.5% of fed females and unfed adults survived over winter, respectively On Long Point, 56.4% of fed females and 23.6% of unfed adults successfully overwintered. Longevity of fed females and u nfed adults was increased by >2 mo at the northern localities compared with Long Point, although survival rates for unfed nymphs at the nort hern sites and on; Long Point were similar. Females within the four ha bitats on Long Point, and at Kenora and Ottawa, laid eggs from late Ap ril to mid-May, whereas eggs were deposited in late June at Hearst. Em ergence of larvae from eggs began in late July or early August on Long Point and at Ottawa. Larvae were first observed in early October at K enora, and no larvae emerged during 1992 at Hearst. Some eggs that ove rwintered during 1992-1993 at the northern sites were viable; however hatching rate was <10%. The minimum duration of the life cycle of I. s capularis is extended when ticks are introduced into regions of the pr ovince with seasonal degree-day accumulations lower than those observe d on Long Point. Delays in deposition of eggs and emergence of larvae at Hearst and Kenora were likely a result of insufficient accumulation of degree-days above threshold temperatures for development in 1992. Though some eggs can overwinter successfully suggesting that latitude- related reduction in seasonal temperature may not limit distribution o f this tick in Ontario, hatchability was low. This factor, combined wi th innate incremental mortality at each instar, difficulty in finding a mate, and low density of medium to large mammal hosts for adults, ma y mitigate against establishment of I. scapularis by introduction of i ndividual ticks into certain northern regions.