Background: The multimillion-dollar avocado industry is threatened by a number of serious insect pests, including at least seven species of Curculionidae. Of these, three Conotrachelus species are known to develop and feed on avocados: Conotrachelus aguacatae Barber, Conotrachelus perseae Barber and C. serpentinus (Klug); the first two are of economic importance. Recently, a series of unrecognised Conotrachelus was intercepted with avocado and other commodities by the USDA at various southern U.S. ports of entry. The species most closely resembled the U.S. native Conotrachelus posticatus Boheman. Given the threat posed by certain species of Conotrachelus to avocado, the identity and biology of intercepted unknown Conotrachelus species becomes a matter of much concern for regulators due to the potential risk posed by non-native species to local agriculture. This study aims to determine the identity, which in turn may shed light on the biology and native distribution, of possible new non-U.S.-native weevils and provide the tools necessary to distinguish amongst phenotypically similar native species. New information: Amongst the unknown Conotrachelus weevils intercepted with avocados at certain U.S. ports of entry is Conotrachelus lobatus Champion. This poorly known species resembles a commonly collected, phenotypically variable indigenous U.S. species, Conotrachelus posticatus, which, on occasion, is also intercepted with avocado. Conotrachelus lobatus has been collected, since the early 1900s until today, along a narrow corridor in the southwest Mexican states of Michoacan, Jalisco and Nayarit. Specimen label data in natural history collections suggests the presence of this species in large numbers in early July in the avocado growing region of Mexico and, based on notes from former curators, appears to breed in acorns of the Mexican endemic oak species Quercus obtusata. The interception of C. posticatus and C. lobatus wth avocado does not imply strict biological association, however it reveals an important pattern of a non-native species' potential for introduction and its potential vector. Understanding all aspects of an organism's biology will better equip growers, as well as regulators, with effective and well-informed management strategies. Characters are imaged and discussed in order to help distinguish some Conotrachelus species belonging to Conotrachelus group II designated by Schoof (1942). Some characters of particular importance are the shape of the metauncus; shape of the lateral margin of the elytra and presence/absence of costate first and second elytral intervals. This study includes high-resolution images of seven Conotrachelus species, including the known avocado pests C. aguacatae and C. perseae, as well as the first images of C. lobatus, C. scoparius Champion and C. squamifrons Champion. The latter three species are not USA natives and were not included in Schoof's work. This study also confirms the important role played by natural history collections in anchoring the species' name through the study of types, which allows for the linking of biological and distribution data over time. Lectotypes are herein designated for C. lobatus and C. squamifrons.
