Thirteen new species of Laemosaccus Schönherr in two species-groups are described from the eastern and southwestern USA and Baja California: from the USA, Laemosaccus obrieni Hespenheide, new species, Laemosaccus andersoni Hespenheide, new species, Laemosaccus arizonensis Hespenheide, new species, Laemosaccus bimaculatus Hespenheide, new species, Laemosaccus burkei Hespenheide, new species, Laemosaccus clytrinoides Hespenheide, new species, Laemosaccus howdenae Hespenheide, new species, Laemosaccus browerorum Hespenheide, new species, Laemosaccus rileyi Hespenheide, new species, Laemosaccus vaurieae Hespenheide, new species, and Laemosaccus gossypii Hespenheide, new species (nine of these also occur in México); from Baja California, Laemosaccus westcotti Hespenheide, new species and Laemosaccus peninsularis Hespenheide, new species. The previously described Laemosaccus nephele (Herbst) and Laemosaccus texanus Champion are redescribed, and lectotypes are designated for Curculio nephele Herbst and Curculio plagiatus Fabricius. A key is provided for the treated species in genus, and larval and adult host plants are recorded. All but three of the previously undescribed species appear not to have been recognized because of their close resemblance to L. nephele, a putative Batesian mimic of chrysomelids of the subfamily Clytrinae and additional putative Müllerian co-models. That evolutionary selection might produce groups of species difficult to recognize (“mimetic homoplasy”) is discussed and suggested that it may be more frequent in other groups than is currently realized.