The general selective toxicity ratio of twelve acaricides to avoid the confusion result from the use of two selective ratios, at LC50 and LC90 levels, was determined. The relative toxicity of the tested com­pounds against S.gilvifrons and its prey T.urticae, revealed that dicofol was the most effective compound. whereas fenpyroximate was the least effective against the mite at each of LC50 and LC90 !eels. Results also showed that fenpropathrin had the highest toxicity, at the same former levels, while propargite (Comite) had the lowest toxicity at LC50 level and propargite (Acargite) at LC90 level against S.gilvifrons. The value of the general selective toxicity ratio recommended fenazaquin, propargite (Acargite), azocyclotion, dicofol, ethion, propargite (Comite), bromo­propylate, hexythiazox, profenofos and fenpyroximate as the safest acaricides for S.gilvifrons as compared to its prey T.urticae.