Immunoblotting experiments were performed using CryIC and CryIA(c) Bacillus thuringiensis δ‐endotoxins to detect the presence of specific toxin binding proteins on Spodoptera littoralis brush border membrane vesicles. The CryIC toxin binds two proteins of 40 and 65 kDa and the CryIA(c) binds a protein of 40 kDa. The CryIA(c) toxin also binds faintly to a 120 kDa protein on S. littoralis brush border membrane vesicles as does a polyclonal antiserum raised against a putative CryIA(c) 120 kDa binding protein from Manduca sexta . The 40 kDa CryIC binding protein was partially purified by affinity chromatography and is therefore a strong candidate for in vivo S. littoralis CryIC toxin receptor.