Two anti-peptide antisera (anti-A and anti-B) raised against Gryllus bimaculatus allatostatin A1 (Grb-AST A1) and B1 (Grb-AST B1), respectively, were applied in the peroxidase-antiperoxidase (PAP) immunohistochemical technique on complete series of sections from the brain, suboesophageal ganglion, corpora cardiaca (CC), and corpora allata (CA) of G. bimaculatus. Both antisera yielded intense staining of numerous cells and nerve fibres. Serial sections, alternately stained with anti-A and anti-B confirmed that the anti-B generally stained more cells and nerves. Extensive immunoreactivity in the retrocerebral complex suggests that the CC and CA may represent a storage and/or release site for both allatostatin types or allatostatin-like molecules produced in the brain., Günther Witek, Peter Verhaert, Matthias W. Lorenz, Klaus H. Hoffmann, and Lit