Use of the median process of the pygophore in the identification of Rhodnius nasutus, R. neglectus, R. prolixus and R. robustus (Hemiptera: Reduviidae).

The morphometrics of the median process of the male pygophore of four species of blood-sucking bugs (Rhodnius prolixus, R. robustus, R. nasutus and R. neglectus) were compared using one-way analysis of variance. Although there were no significant differences in the pygophoral patterns within the R. nasutus-R. neglectus or R. prolixus-R. robustus species pairs, there were clear-cut differences between them; the median process of R. nasutus-R. neglectus is stout and subtriangular whereas that of R. prolixus-R. robustus is more narrow and elongated. The basal width of the process, classically used to separate R. robustus from R. prolixus and R. nasutus from R. neglectus, seems to have little taxonomic value. Other characters which have been assumed to be species-specific should be subjected to a similar quantitative analysis.