The biological control of the snails intermediate hosts of Schistosoma mansoni* is one of the accepted options to fight schistosomiasis . For the control of schistosomiasis , one strategy is based on the premise that resistant snails to parasite infection could be used as biological competition agents to replace existing susceptible snails in endemic areas. Therefore , the current studv was designed to investiuatejihe influence of] environmental iactors on copulation behaviour of Biomphalaria snails under various laboratory conditions^ These factors are : light, darkness , starvation , pH and association with non- target snail species mseid^r to obtain information on the ecological conditions for reproduction of the resistant species.The data obtained showed that , copulation behavior was enhanced by different environmental factors and revealed the best modular system for snail reproduction . Itoaas-aBo noticed that, non-target snail species or the resistant snails affect crossing among the target snails .Moreover, resistant snails recorded more tolerance against abnormal environmental conditions.