Biological Study of Cucurbit Fruit Fly, Dacus ciliatus (Loew) on Constant Temperatures

of the cucurbit fruit fly Dacus ciliates (Loew) (Diptera: Tephitidae) was studied at constant temperatures (15, 20, 25 and 30 ± 1 ̊ C). The development of immature stages was accelerated by rising of tested temperatures. Development stages average of eggs, larvae, pupal and pre-oviposition period ranged between (31.13 and 3.47), (37.07 and 5.80), (30.27 and 7.20) & (33.13and 5.73) days on 15 and 30 ̊ C, respectively. Also, total immature stages ranged between 98.47 and 16.47 days on 15 and 30 ̊ C, respectively. Whereas, Generation period ranged between 131.60 and 22.20 days on 15 and 30 ̊ C, respectively. Additionally, adult females survived slightly longer than males, also life span, and sex ratio. While the estimated (t o ) threshold temperatures stages eggs, larval, pupal and pre-oviposition period were 15.05, 13.39, 10.64 and 13.11 heat units (U.T.) at 15, 20, 25 and 30 ̊ C ±1 ̊ C, respectively. Based on 30 ̊ C estimations are required to complete the development of all immature stages. Also, Thermal requirements (K) D.D. ' s were estimated to be 58.35, 97.07, 133.58 & 103.81 for eggs, larval, pupal and pre-oviposition periods at 15, 20, 25 and 30 ̊ C ±1 ̊ C, respectively. And development for one generation required 386.17 D.D′s, The study showed that with the identif ication of threshold temperatures (t o ) and thermal units (K) for generation calculated nine expected generations in the field they: two generations in spring, four generations in summer, two generations in autumn, one generation in winter.