Abstract

wline"> The generalist predatory mite Typhlodromus bagdasarjani W. & A. is an indigenous phytoseiid predator which is recorded in plants infested by two spotted spider mite, Tetranychus urticae Koch, eriophyoids, tydeids or insect pests such as thrips and whiteflies. The present work aimed to study the developmental stages of the predator fed on two spotted spider mite under laboratory conditions, especially in high humidity. T. urticae was maintained on whole bean plants, Phaseolus vulgaris L. Predatory mite reared on bean leaf arenas in petri dishes and fed on T. urticae. Even-aged eggs of T. bagdasarjani were obtained by placing gravid females on detached bean leaves. Every 24 h, newly laid eggs were collected. Eggs were transferred into separate Petri dishes with about 10 mobile immatures of T. urticae on bean leaf deposited on cotton. Drops of water were added daily on cotton to maintain suitable relative humidity. Observations were made at intervals of 24 hours and mortality and every stage were recorded until adults emerged. The newly emerged females were paired with males obtained in the experiment or taken from the colony at the same temperature. The couple was kept together up to the end of the study and dead males were replaced by new ones. Daily observations were then made to determine pre-oviposition, oviposition and post-oviposition periods. The observations were continued until all individuals had died. Therefore, duration of stages of males and females were determined. Experiments were conducted at 25±1ºC, 75±5% RH and 16:8 h L: D photoperiod. The developmental time significantly differed between males and females (F= 5.35, P= 0.02). It recorded 7.28± 0.17 and 6.66±0.18 days for females and males, respectively. So, the males emerged earlier than the females. Females longevity also differed significantly from that of males (F= 27.29, P= 0.00). It was 19.57± 1.46 and 7.5± 1.68 for females and males, respectively. Pre-oviposition, oviposition and post-oviposition periods in average were 3.04, 12.38 and 3.95 days, respectively. The shortest stage was in larvae. Deutonymphal stage in both males and females was about two times longer than protonymphal stage.