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Tribe: Cavernicolini (genus: Cavernicola)

The two species of Cavernicola are small Triatominae (adults up to 11 mm in length) with unusually shaped head and neck strongly reminiscent of some Apiomerinae. They seem invariably associated with bats and bat roosts, but will feed from other vertebrates in the laboratory. The tribal, generic, and species concepts are entirely morphological.7,46

Tribe: Rhodniini (genera: Psammolestes, Rhodnius)

The three species of Psammolestes are small Triatominae (adults up to 15 mm in length) with truncated heads. They are invariably associated with nests of woven sticks as made by dendrocolaptid or furnariid birds (irrespective of the vertebrates currently occupying the nest). Although considered a monophyletic genus by morphological and behavioral similarity, this is difficult to reconcile with their distribution: Ps. arthuri occurs in the llanos of Colombia and Venezuela north of the Amazon region, while Ps. tertius and S. coreodes seem to form a cline down the caatinga- cerrado-chaco corridor of open vegetation south of the Amazon region. Ps. coreodes has strong ecological interactions with thornbird nests in the Southern Pantanal region of Brazil47 and has recently been reported in the Gran Chaco and La Pampa in Argentina.48,49

By contrast, Rhodnius species are distributed throughout the Amazon region, and into the llanos northwards, and the caatinga and cerrado to the south. They are primarily associated with palmtree crowns, but also occur in bird’s nests and in domestic and peridomestic habitats. By morphological, behavioral, anatomical, and genetic features, they appear to form a monophyletic genus50 with two main lineages: the “prolixus—robustus” group (prolixus, robustus, milesi, neglectus, neivai, dalessandroi, domesticus, nasutus, barretti, zeledoni, montenegrensis) mainly east of the Andes, and the “pictipes” group comprising one subgroup east of the Andes (pictipes, stali, brethesi, paraensis, amazonicus) and one subgroup west of the Andes (pallescens, colombiensis, ecuadoriensis).51 R. pictipes may be closest to the ancestral form, since it is the most widely distributed and of more generalist habit, and shares genital characteristics with other Triatominae that are not shared with other Rhodniini except R. stali.52

The Rhodniini appear to represent a monophyletic tribe, with clear morphological, physiological, anatomical, and genetic characteristics that distinguish them from other

Triatominae. Relationships between the two genera are less clear, largely because of the paucity of studies on Ps. arthuri. Various phylogenetic studies based on MLEE,53 mtDNA,54,55 or ribosomal mtDNA56 indicate paraphyly between Rhodnius and Psammolestes. The two genera have different morphologies and ecological habits, but both are arboricolous. They seem to represent ecological adaptations to either the tree crown (Rhodnius) or the bird’s nests (Psammolestes).

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