Monoclonal antibodies, raised against alpha-latrotoxin, have been used on serial sections of the venom glands with localization by indirect immunofluorescence. Colloidal gold immunovisualization and electron microscopy were used in order to localize the structure of the cells that synthesize and store the toxin. The antibodies were able to recognize the native toxin revealing its presence mainly in the 'replacement cell' layer, a layer of cells close to the muscular sheath of the gland. These cells apparently replace the disintegrated epithelial cells at the end of the holocrine cycle. Gold grains were predominantly observed around the free ribosomes and the secretion droplets of the 'replacement cells'.