Some Hemiptera (Triatomidae) common in Brazil (Panstrongylus megistus, Triatoma brasiliensis, Rhodnius prolixus) presented in the external tegument erythropterin, xanthopterin and possibly 3, 4, 7 - trioxypteridine. Most of the coloured extracts showed in the visible a sharp absorption at 400 nm suggesting its anthocyan character. Neither leuco nor biopterin were detected. The Rf was obtained by thin layer chromatography and the absorption measured spectrophotometrically in a Zeiss PQMII apparatus.