Effect of temperature and humidity on longevity of unfed adults and on oviposition of engorged females of Dermacentor reticulatus (Ixodidae).

The effect of ambient temperature and relative humidity on longevity of unfed adult ticks and on oviposition of engorged female ticks of Dermacentor reticulatus was examined. The 50% mortality time of unfed adult ticks, incubated at 5 degrees C, 10 degrees C, 20 degrees C and 27 degrees C and humidities of 15%, 50% and 100%, increased irrespective of their sex with rising relative humidity and decreasing temperature. It was longest at 5 degrees C and 100% r.h. being 617.8 days and shortest at 27 degrees C and 15% r.h. amounting only to 33.6 days. All unfed ticks survived an incubation of 150 days at -10 degrees C and 15%, 50% and 100% r.h. as well as an exposure of 180 days at 0 degrees C and 100% r.h. At 0 degrees C the percent survival was 75% for the males and 40% for the females at 50% r.h. but 100% for males and 95% for the females at 15% r.h. after exposure of 180 days. Oviposition of engorged females occurred at a temperature range of 10-27 degrees C, at 10 degrees C merely at 50% and 100% r.h. The percentage of ovipositioning females amounted to at least 80% apart from 10 degrees C and 50% r.h. being only 10%. The egg index and the egg conversion index as well as the larvae index and the larvae conversion index generally increased with rising temperature and relative humidity. The indices were lowest at 10 degrees C and 50% r.h. and were highest at 20 degrees C and 27 degrees C at 100% r.h. The reproduction capability of engorged female ticks, held at -10 degrees C, 0 degrees C and 5 degrees C and 15%, 50% and 100% r.h. and transferred to 20 degrees C and 95% r.h., persisted for 10 weeks at -10 degrees C and for 2 weeks at 0 degrees C at the most, but for at least 20 weeks at 5 degrees C. There were no significant differences of the preoviposition periods, egg indices and larvae indices as well as of the minimum embryonic developmental times and hatching rates with regard to the preceding incubation conditions and the length of the ticks' exposure.