Triatominae bugs aggregate around their faeces which carry an assembly signal. Here the biological role of the signal is studied for Triatoma infestans. We describe a stereotypic behaviour of T. infestans where the insects exit from shelters in order to defaecate. A higher concentration of faecal depositions are found at accesses to refuges. In choice experiments where faeces were presented in association with artificial refuges to ascertain whether this affected election of shelters by the bugs, shelters with faeces, either inside or outside, were significantly preferred by bugs. We conclude that faeces help in the selection of refuges by these insects and the role of excrement as a chemical signal for a shelter under use is discussed.