Heat-shock proteins (Hsp) provide the cellular and full-body adaptation of animals to various adverse environmental conditions. The hsp70 is believed to play a major role in the biological adaptation of all organisms studied so far. In all animals the regulatory regions of the heat shock genes studied include several conservative promoter elements HSEs (heat shock elements) that are needed to bind heat-shock transcription factor (HSF). The promoter regions of the hsp70 genes are extremely conserved and, hence, it has been generally accepted that they are universal and can operate in species that belong to different phyla. In the present work, we performed a comparative analysis that revealed characteristic differences in the hsp70 promoters of two Diptera species, i.e., Drosophila melanogaster and highly thermotolerance soldier fly Stratiomys singularior. We measured promoter activity in D. melanogaster cell culture exploring in vitro luciferase reporter assay. The analysis demonstrated significantly higher strength of D. melanogaster promoters despite that comparable numbers of HSEs were present in both species. These drastic differences in the promoter strength are probably due to the absence of GAF-binding sites, which are necessary for the efficient functioning of D. melanogaster hsp70 promoters. In contrast, the comparison of hsp83 promoters isolated from these two species has not shown significant differences. Our results demonstrate existence of different evolutionary trends in the regulation of the hsp70 expression even within the same order (Diptera)