The life stages comprise egg, larva, protonymph, deutonymph and adult (female and male). Females lay up to 80 eggs at an average of five per day (more eggs are laid in areas of high than low numbers of prey). A moult occurs between each post-egg stage. Eggs are oval, translucent, and change from light to dark orange as they age. Larvae are six-legged and do not feed, whereas the nymphs and adults are eight-legged and all prey on spider mites. The ratio of female:male offspring is often 4:1, although more males are produced in low prey densities or after female starvation.
The time taken to develop from egg to adult is affected by temperature, relative humidity (R.H.), type of plant host and prey availability. The egg stage is most sensitive to low humidity and needs an R.H. of more than 60 per cent (at 23°C) to hatch. For successful development from egg to egg, the temperature needs to be at least 11°C. At 80 per cent R.H., with plentiful Tetranychus prey and bean (Phaseolus lunatus) as host plant, development from egg to adult took 4.6, 3.8 and 3.6 days at 25, 30 and 35°C respectively. Survival of immatures decreases over 30°C, regardless of humidity. At 70-75 per cent R.H., eggs and nymphs could not survive at 40°C. In glasshouses, where temperatures ranged between 11.5 and 23.5°C and R.H. between 36 and 95 per cent, developmental time was about 11 days.
(Laing, 1968; Takafuji and Chant, 1976; Badii and McMurtry, 1984; Sabelis, 1985a, b, c; Perring and Lackey, 1989; Takahashi and Chant, 1992, 1994; Zhang, 2003; Vanas et al., 2006)