The sequences are given of two peptides (secapin and melittin F) whose isolation from the venom of the common European honey bee (Apis mellifera) has previously been described [Gauldie et al. (1976) Eur. J. Biochem. 61, 369--376]. Some structural studies on the known peptide 401 (MCD peptide) are described. The positions of the two disulphide bridges in peptide 401 have been determined by (an essentially) novel method.