Multiple origins of ant-associated biology in the spider beetles (Coleoptera: Ptinidae)

The spider beetles are morphologically diverse family comprised of approximately 700 species in 70 genera. Previous authors have divided the family into eight generic groups, but there are eight myrmecophilous (ant-associated) genera that have never been placed in any of these groups. Myrmecophilous spider beetles generally bear strange or unusual characteristics such as trichomes, modified antennae, mouthparts or body forms, which has made it difficult to make any statements of homology with regard to other spider beetles. This study presents a preliminary morphological, cladistic analysis of at least one representative of nearly all species groups, including representatives of eight myrmecophilous genera. Myrmecophiles are generally plesiomorphic, rather than derived, and the majority of spider beetles appear to be highly autapomorphic. The evolution of myrmecophily and informative characters in determining spider beetle relationships are discussed.