We examined the esterases present in the hemolymph and Malpighian tubules of "Kissing bug", Triatoma infestans (Triatominae, Heteroptera) by polyacrylamide gel electrophoresis. Six esterase bands were observed and were designated EST 1 to EST 6. EST 1, 4, 5 and 6 were exclusive to hemolymph, whereas EST 2 and 3 were found only in Malpighian tubules. Each tissue had a characteristic esterase pattern, which may be related to its functional role. The four hemolymph esterases hydrolyzed a-naphthyl acetate. One of these enzymes was classified as a carboxylesterase (EST 4), and another was an acetylesterase (EST 6). The other two enzymes (EST 1 and 5) could be either carboxylesterases or serino-proteases with an esterolytic function, as they were selectively inhibited by phenylmethylsulfonyl fluoride (PMSF). Absence of genetic variability could be due to high inbreeding.
