A major use of GM crops is in insect control through the expression of the "cry" (crystal delta-endotoxins) and "Vip" (vegetative insecticidal proteins) genes from "Bacillus thuringiensis" (Bt). Such toxins could affect other insects in addition to targeted pests such as the European corn borer. Bt proteins have been used as organic sprays for insect control in France since 1938 and the US since 1958, with no reported ill effects. "Cry" proteins selectively target Lepidopterans (moths and butterflies). As a toxic mechanism, "cry" proteins bind to specific receptors on the membranes of mid-gut (epithelial) cells, resulting in their rupture. Any organism that lacks the appropriate receptors in its gut is unaffected by the "cry" protein, and therefore is not affected by Bt. Regulatory agencies assess the potential for transgenic plants to affect non-target organisms before approving their commercial release.