Biological and Ecological Fitness of the Two-Spotted Spider Mite, Tetranychus urticae Koch (Acari: Tetranychidae) on Certain Host Plants The comparative population growth parameters of the two-spotted spider mite,  Tetranychus urticae Koch on cucurbits vegetable crops; Sudanian, Musk and Snake melons commonly planted in numerous districts of Egypt were studied. These parameters were estimated at 25 ± 1°C, 60 ± 5% R.H. and a photoperiod of 14:10 hrs. (L: D) daily. Developmental time, survival to adult stage and egg hatchability were similar  among the three host plants, hut significant variation in  fecundity and longevity, resulting in  large differences tor population growth parameters. such as the intrinsic rate of natural increase (r_m),  net reproductive rate (R_o) and finite rate of increase(λ) were detected. Sudanian melon was the most favorable host for the two-spotted spider mite with r_m  (0.297),  followed  by Musk melon (0.243)  off springs/female/day. The slowest population growth was observed on Snake melon with r_m (0.231) off springs/ female/day.