The life cycle and biological characteristics of Dermacentor silvarum Olenev (Acari: Ixodidae) under field conditions.

In this study, we investigated the life cycle and biological characteristics of all developmental stages of Dermacentor silvarum under field conditions in Hebei province in North China. Larvae, nymphs and adults were fed on rabbits, and maintained under natural lighting and climate conditions. Ticks were released into a confined plot located in natural tick habitat, and we observed the host questing behavior and seasonal occurrence. Due to a behavioral diapause in females and the synchronization of oviposition and larval hatching, D. silvarum only active from late February to early September under field conditions. The duration of the life cycle of D. silvarum was highly variable due to different preovipositional and egg hatching periods for ticks engorging in March, April or May. The developmental periods of larvae (18 days) and nymphs (29 days) under field conditions were similar to those under laboratory conditions. Moreover, there was a highly significant correlation between engorged body weight of females and egg masses laid (r=0.76, p<0.001). The female reproductive efficiency index (REI) in March, April and May was 5.7, 7.1 and 6.2, respectively. Finally, we also observed different ovipositional patterns between females that engorged in the field and those that engorged under laboratory conditions.