Five hundred and fifty eight spiders belonging to 11 families of order Araneae were associated with T. urticae and collected on clover and cotton crops at Qaha research station in Qalubyia governorate, Egypt during two successive years, 2013 and 2014. During the period of study, Salticidae was the most abundant of the collected spider followed by Theridiidae, Thomisidae, Philodromidae, Dictynidae, Eutichuridae (Miturgidae), Araneidae, Linyphiidae, Lycosidae, Agelenidae, and Gnaphosidae. The number of the collected spiders, families and percent occurrence of each family varied on the studied crops in different seasons. On clover, the collected families did not include Gnaphosidae in both years of study in addition to Araneidae in 2013 and Lycosidae, Philodromidae and Agelenidae in 2014. On cotton, Lycosidae and Agelenidae were not collected in both years in addition to Gnaphosidae in 2014. Changes of population densities of the monthly collected spiders and their prey, T. urticae, ran nearly in parallel during the whole seasons of cotton with peak in September and up till the prey peak on clover in March. Although the population of T. urticae decreased in the next months following the peak on clover, the spiders continued increasing to reach their peak in May 2013 and 2014. The total number of collected spider's movable stages was higher in 2013 than 2014 on each crop and on cotton than clover in each year of study. On the other hand, the total number of T. urticae collected was higher in 2014 than 2013 on each crop and on clover than cotton in each year of study. Laboratory studies on life stage duration, food consumption and predation rate of early immatures and adult female of Thanatus albini, Steatoda triangulosa and Thomisus spinifer (family Philodromidae, Theridiidae, Thomisidae, respectively), showed the efficacy of the three selected spider species as predators on adult Tetranychus urticae. Immatures and adult females of the studied spiders consumed more and lived longer when fed on females than males of T. urticae. In immature spiders, the number of consumed prey/spider, the daily predation rate and mostly the stage duration (except S. triangulosa) gradually increased by increasing age from the first to third spiderling. In female adult spiders, the 3 parameters, except predation rates of Thomisus spinifer, were the highest in female T. albini, followed by T. spinifer then S. triangulosa. The significance of the obtained result was discussed.