Triatomines of the Genus Rhodnius Do Not Mark Shelters with Feces

Aggregation to volatile compounds emitted by feces has been demonstrated for several triatomine species. This signal guides the insects to suitable places that offer physical protection while providing contact with conspecifics. Though the use of aggregation marks has also been reported for Rhodnius spp., it is still unclear whether feces really cause these insects to aggregate inside shelters. In two-choice assays using artificial shelters, we found that refuges associated with a blend of synthetic compounds based on volatiles released by the feces of some triatomine species and reported to be attractive to several species, did not induce shelter choice in Rhodnius prolixus Stål, 1859. In addition, we show that refuges associated with feces of conspecifics did not induce shelter choice in R. prolixus, R. robustus Larrousse, 1927, R. neglectus Lent, 1954, and R. ecuadoriensis Lent and León, 1958. In contrast, as expected, control experiments with Triatoma infestans (Klug, 1834), another triatomine known to aggregate in shelters marked with feces, definitely showed preference for shelters containing feces of conspecifics. Our results clearly show that volatile signals associated with feces do not mediate shelter choice in Rhodnius spp. As a consequence, a paradigm shift will be necessary and, consequently, ab ovo investigations on the clues inducing aggregation behavior in these species.