The average adult body length is about 450 micrometres (0.45 mm) with a  range of 340-530 micrometres.


  • The average weight of a fed ovipositing female is 16.4 microgrammes (0.0000164 grammes) (McMurtry and Rodriguez, 1987).
  • Males reach maximum weight soon after the moult to the deutonymph.
  • Female weight increases until egg-laying begins and decreases after it stops. (Takafuji and Chant, 1976; Sabelis, 1985a)

Life expectancy

Temperature, relative humidity, prey availability and host plant identity all affect longevity.

Under constant favourable conditions of about 26°C and 80% R.H., with plentiful Tetranychus prey and lima bean (Phaseolus lunatus var. macrocarpus) as host plant, total lifespan averaged 28.5 days for females and 31.5 days for males.

When reared in similar conditions but on different host plants, P. persimilis lived for an average of 20.7 days on snap bean (Phaseolus vulgaris), but only 11.3 days on tomato (Lycopersicon esculentum). The low longevity on tomato was attributed to the detrimental affects of exudates from tomato leaf trichomes (hairs). (Laing, 1968; Gillespie and Quiring, 1994; Sabelis, 1985b; Takahashi and Chant 1994).