DEVELOPMENTAL BIOLOGY AND FUNCTIONAL RESPONSE OF THE PREDATORY MITE PROPRIOSEIOPSIS MEXICANUS (GARMAN) (ACARI: MESOSTIGMATA, PHYTOSEIIDAE)

Studies were conducted to determine the life cycle, demographic parameters and the functional response of the predatory mite Proprioseiopsis mexicanus (Garman) when fed on the red spider mite Tetranychus urticae Koch complex. Under ambient laboratory conditions of 28 ± 2°C and 65-95% RH, the average durations between the developmental stages were 43 hours for eggs, 13 hours for larvae, 26 hours for protonymphs and 18 hours for deutonymphs, thus giving a developmental time from egg to adult of 100 hours with a mean survivorship of 91.5%. Oviposition started on the second day of adulthood with a mean oviposition period of 11.2 days and mean fecundity of 29.6 eggs per female. The net reproductive rate (R0) was 22.8 female offspring per female recorded throughout a generation time of 13.3 days. The capacity for increase (rc) and the intrinsic rate of increase (rm) were 0.2355 and 0.2970 respectively, with a doubling time (DT) of 2.9 days. The sex ratio of 5:2 was biased towards the females with the female survival averaging 3 days longer than the male (36 days). Prey preference studies revealed that the larval stage was the most preferred over the eggs, nymphs and young adults. In general, the functional response was adequately described by the Holling s Type II model. In a 24 hours observation, a gravid female maintained a high rate of consumption of 70% at a prey density of 20 eggs per female before the rate tapered off to a satiation point to a threshold density between 35-40 eggs per female.