FIELD AND LABORATORY STUDIES ON THE TIMING OF OVIPOSITION AND HATCHING OF THE WESTERN BLACK-LEGGED TICK, IXODES PACIFICUS (ACARI, IXODIDAE)

The timing of oviposition and hatching of Ixodes pacificus was investi gated in the field and at constant temperatures in the laboratory. Rep lete females held at temperatures between 9 and 29 degrees C began dep ositing eggs a mean of 9-70 days after drop off. Egg masses held betwe en 12 and 25 degrees C commenced hatching 25-178 days after the onset of oviposition. Eggs held at 9 or 29 degrees C did not hatch. The lowe r temperature thresholds for development (LTD) for oviposition and hat ching were 6.5 and 9 degrees C, respectively. The number of degree day s required for oviposition and hatching was 173 and 588, respectively. Replete females placed in the field on 2 December through to 8 March deposited eggs from 2 February through to 24 April; the eggs commenced hatching between 2 July and 21 August. Unfed larvae from two of 20 eg g masses survived through the winter and fed readily when exposed to d eer mice (Peromyscus maniculatus) on 22 April. Replete larvae were ret urned to the field and moulted between 9 and 21 August. Larvae exposed to deer mice in August, 4 weeks after hatching, also fed readily. Alt hough further studies are needed to clarify the timing of nymphal deve lopment, the present study suggests that I. pacificus requires more th an 1 year to complete its life cycle.