Effects of photoperiod on the host-feeding and development of Haemaphysalis flava nymphs (Acari : Ixodidae)

Abstract

The effects of photoperiods on host-feeding and development in Haemaphysalis flava nymphs were observed at 25℃ under four different photoperiods (10L-14D, 12L-12D, 14L-10D, and 16L-8D). The rate of engorgement was significantly reduced by exposure to 10L-14D or 12L-12D photoperiods from the egg to the unfed nymphal stages. The development of the engorged nymphs was also retarded or arrested by exposure to 10L-14D or 12L-12D photoperiods. These results suggest that diapause occurs in the unfed and engorged nymphs that have been exposed to short-day or 12L-12D photoperiods from the egg stage. However, the rate of engorgement of the nymphs was relatively high when they were reared under a short-day photoperiod of 10L-14D. In addition, evidence of commencement of apolysis (the developmental change in the cuticle) was found in the engorged nymphs at a 10L-14D photoperiod. Thus, the diapause of the nymphs appears to be light. Although the diapause of H. flava nymphs is light, most of those that are molted from the engorged larvae in autumn may not develop to adults within the same year.