MATING BETWEEN DIAPAUSING AND NONDIAPAUSING STRAINS OF THE CITRUS RED MITE, PANONYCHUS CITRI (MCGREGOR)

The reproductive compatibility between diapausing (DP) and nondiapausing (C) strains of the citrus red mite, Panonychus citri (M.), was determined by crossing experiments. Mating between the two strains was unrestricted, but copulation between C females and DP males was often broken off prematurely, whereas copulation in the reciprocal cross was of normal duration. Diapausing males showed a strong preference for guarding quiescent female deutonymphs of their strain prior to copulation, whereas C males did not. However, males of either strain showed no preference between adult females, resulting in only a partial, one-sided premating isolation between strains. No adult females were produced in the progeny from either interstrain cross, showing reproductive incompatibility is complete. Hatchability of the eggs from the cross between DP females and C males was significantly lower than that from the cross between C females and DP males, or from the intrastrain crosses, suggesting that even though some of the eggs in the former cross were fertilized, they died during embryonic stages. This possibility was supported by the observation that, for DP females mated with a C male, the second intrastrain mating was almost totally ineffective. Also, for C females mated with a DP male, a second intrastrain mating was often ineffective, but to a lesser extent than for DP females. When the two strains coexisted, effective mating was severely curtailed for both strains. The results explained the low proportion of females from overwintered DP eggs in a pear orchard in which the two strains coexisted the previous autumn.