Laboratory investigations were carried out to asses the effect of some proteases inhibitors on the reproductive potential of Culex pipiens females resulted from larvae treated with different protease inhibitors. The fecundity and engorgement of
symbiotic and aposymbiotic C. pipiens females were significantly reduced. The blood meal digestion period increased significantly. On the other hand, enzyme band with molecular weight of 40 KDa which may be cysteine protease was detected in untreated symbiotic and aposymbiotic female midguts. The results may explain that the absence of this enzyme bands in treated female midguts may be due to the inhibition caused by (E-64) a cysteine protease inhibitor.