Current experiments were conducted to assessment, the relative toxicity of four chemicals and action mechanism for two insecticides (Abamectin and Ethion), and two plant oils; Allium sativum  (Liliaceae) oil and Melia azedarach  (Meliaceae) oil against females adult and eggs of two spotted spider mite T. urticae and T. cucurbitacearum. In addition to evaluation the side effects of “sub-lethal dose” of these chemicals on “biological-aspects” for the tested insect stages “spider mites” using standardized method for bioassay. Sub-lethal doses effects of these chemicals on some biological-aspect were evaluated. Data obtained resulted that, abamectin gave highly toxic compound and ethion was in the 2^nd rank, while A. sativum oil and M. azedarach oil showed the lower-toxic against females-adult of T. urticae, and T. cucurbitacearum. Also, the results showed that, the two compounds “abamectin and ethion” showed highly-toxic ovicide on egg-stages of T. urticae and T. cucurbitacearum, while A. sativum oil and M. azedarach oil, appeared least-toxic against eggs-stages of T. urticae, and T. cucurbitacearum. The results also, indicated that the high reduction percentage in eggs laying capacity with(63.19 and 62.94%) were found when females-adult of T. urticae and T. cucurbitacearum, treated with “LC₅₀ value” of abamectin, while the lowest reduction (6.63 and 11.64 %) was obtained in case of the treatment with LC50 of M. azedarach of them. Abamectin and ethion were most effect against motile-stages, whilst M. azedarachtin oil, showed least-effect against motile-stages of T. urticae and T. cucurbitacearum, in field condition.