Effect of temperature and sperm supply on the reproductive potential ofTetranychus evansi (Acari: Tetranychidae)

The biology ofTetranychus evansi Baker and Pritchard was studied at five different temperatures on excised leaves ofSolanum douglasii Dunal. The theoretical lower threshold temperature of development was ca. 13°C. The combined immature stages required ca. 148 day-degrees for completion. Progressively later initiation of mating resulted in higher peak proportions of females produced, up to an 8-day period between emergence and mating at 30°C. The proportion of male offspring always increased towards the end of the oviposition period, apparently because of sperm depletion. The calculated intrinsic rate of increase was highest (0.432) at 35°C, the highest temperature tested. At that same temperature, daily oviposition rate and net reproductive rate were maximum (9.5 and 111.77, respectively), and mean generation time and doubling time were minimum (10.92 and 1.6 days, respectively).