In the paper adaptive significance of a confinement of the oviposition of levant viper, Macrovipera lebetina obtusa (Dwigubsky, 1832) to certain embryogenesis stages is considered. It is experimentally proved that the embryos of levant viper have the highest resistance to temperature influences at the time of oviposition and they are capable to survive severe high and low temperatures. In different populations the thermal tolerance of embryos at the stage of oviposition was similar. There is no pronounced intraspecific morphological variability in development of embryos of levant viper by the time of oviposition.