Crossbreeding between Tetranychus urticae females and T. arabicus males as well as reversed crossing between males of the former and females of the latter resulted in giving average offspring of 77.9 and 82.8 individuals/female of which 80.2% and 78.8% were females in the two crossings respectively. Also crossmating between both sexes of F1 gave progeny averaging 84.7 F2 individuals/female of which 81.3% were females. This normal number of progeny/female and egg fertilization percentage unfavoured the separation of the tested mites into two different species. In addition, morphological characters such as shape of lobes of the dorsum integumentary folds and setation of tarsus and tibia I, are similar in the two species. Size of aedeagus knob and its relation to dorsal margin of the shaft are usually similar except knob anterior projection being acute in T. urticae and usually narrow rounded in T. arabicus. This minute difference is not reliable for species separation.