Abstract
Photoperiodic sensitivity of various stages was studied on the diapausing strain of the citrus red mite, Panonychus citri (MCGREGOR), in which egg diapause was determined by maternally controlled photoperiods. In the experiments, one or more stages were treated with short-days (12L-12D) and the remainder with long-days (16L-8D) at 20°C. The sensitivity was demonstrated in all the developmental stages. In particular, when both protonymphal and deutonymphal stages together were exposed to short-days, the diapause incidence was greatly increased. However, 100% diapause incidence was achieved only when the mites were exposed to short-days throughout the developmental period. The adult stage was also sensitive; some females switched over from non-diapausing to diapausing eggs or vice versa, according to photoperiodic regime during the oviposition period. These results combined showed that the effects of long- and short-days were cumulative, and also that the diapause-averting effect of long-days was more pronounced than the diapause-inducing effect of short-days.
