A technique for marking adult insects was worked out, aiming at the individual identification of triatomine bugs. It consists on the development of codes corresponding to numbers (units, tens and hundreds) by means of five basic colours (red, white, blue, green and yellow), represented by colored spots hand-made with enamel paint from the pronotum to the scutellum of the insect, with a fine silk paint-brush. The spots should not reach the overlapped wings, for these often change position, therefore covering the marks. Being the paint indelible and nontoxic, the life-span and the behaviour of the bugs is not affected. The technique may be applied to insects in the laboratory as well as in the field, specially in studies related to Ecology and Behaviour.