Diagnosis. Smaller scarabs, rarely over 15 mm, most are less than 8 mm; elongate to oval. Head with clypeus usually expanded, usually covering mouthparts. Mandibles often reduced. Antennae with 9 segments, club 3-segmented. Mesocoxae usually nearly contiguous, with notable exceptions. Metatibiae usually with 2 apical spurs. Abdomen with 6 visible sternites. Pygidium partially or completely covered by apex of elytra. Tarsi usually with distinct claws.
Classification status. Higher level organization of suprageneric taxa is in need of solid phylogenetic work. The subfamily Aphodiinae (occasionally considered a family) is diverse in morphology and natural histories, showing many potential convergences or parallelisms in characters. Current publications vary tremendously in tribal and subtribal arrangements. For ease in presentation, I choose to use a classification where only full tribes are recognized.
World list of Tribes in the Aphodiinae (click on underlined tribal names for information).
Tribe Corythoderini (not New World)
Tribe Odochilini (not New World)
Tribe Termitoderini (not New World)
Composition. Worldwide, the Aphodiinae contains 12 tribes, approximately 280 genera and 3200 species. As presently understood, the New World fauna contains 9 tribes,128 genera and 816 species.
Thirteen fossil taxa have been described for the New World (Krell 2000, 2006). The majority of them are incomplete impression fossils, whose present generic placements are unknown or at least extremely tenuous. A number of fossils are known in amber or copal from the Dominican Republic and Colombia. To date, none of these has been described, some are presently under study.
Life history. The common name “small dung beetles” is something of a misnomer. While many species feed on dung, many have other habits. Some species are detritivores, psammophiles, saprophages, inquilines with ants or termites, or may potentially be predators. Adults with reduced mandibles are suspected to feed primarily on bacteria or yeast-rich fluids in dung or decaying materials. Larvae of the Aegialiini, with well-developed mandibles, may feed on more solid substances. This difference in structures allows some adults and larvae to occupy very different niches. While some species feed on dung as both adults and larvae (e.g. Cryptoscatomaseter ejectus Gordon and Skelley, feeding on pocket gopher dung), other species have adults and larvae feeding in different situations (e.g. Labarrus pseudolividus Balthasar, adults found on dung, larvae are suspected to be detritivores).
Larvae of numerous species have been collected, reared, but few have been preserved that can be confidently identified and have adequate descriptions. Larval descriptions or diagnoses are available for only 46 New World species. The most recent discussion of each is cited under the appropriate genus account below. However, the majority of these can be found in Jerath (1960) and Ritcher (1966).
Standard collecting techniques usually produce the common species: dung-baited pitfall traps collect mostly surface-dwelling generalist Aphodiini (often only the introduced European species), and collecting at lights yields common Eupariini and Psammodiini. To collect a diversity of Aphodiinae, one must use other techniques (flight intercept traps, barrier pitfall traps, sifting sand or leaf litter, etc.), be persistent, and focus on niches in which the taxa may occur. Alternative collecting techniques that have worked for aphodiines are discussed in more detail by Gordon and Skelley (2007).
Dellacasa, M. 1988a. Contribution to a world-wide catalogue of Aegialiidae, Aphodiidae, Aulonocnemidae, Termitotrogidae (Coleoptera Scarabaeoidea). Memorie della Societa Entomologica Italiana  66: 1-455.
Dellacasa, M. 1988b. Contribution to a world-wide catalogue of Aegialiidae, Aphodiidae, Aulonocnemidae, Termitotrogidae (Coleoptera Scarabaeoidea) Part II. Memorie della Societa Entomologica Italiana 67: 1-229.
Dellacasa, M. 1988c. Contribution to a world-wide catalogue of Aegialiidae, Aphodiidae, Aulonocnemidae, Termitotrogidae (Coleoptera Scarabaeoidea). Addenda et corrigenda (First note). Memorie della Societa Entomologica Italiana 67(2): 291-316.
Dellacasa, M. 1991. Contribution to a world-wide catalogue of Aegialiidae, Aphodiidae, Aulonocnemidae, Termitotrogidae (Coleoptera Scarabaeoidea). Addenda et corrigenda (Second note). Memorie della Societa Entomologica Italiana 70(1): 3-57.
Dellacasa, M. 1995. Contribution to a world-wide catalogue of Aegialiidae, Aphodiidae, Aulonocnemidae, Termitotrogidae (Coleoptera Scarabaeoidea). Addenda et corrigenda (Third note). Memorie della Societa Entomologica Italiana 74: 159-232.
Gordon, R. D., and P. E. Skelley. 2007. A monograph of the Aphodiini inhabiting the United States and Canada (Coleoptera: Scarabaeidae: Aphodiinae). Memoirs of the American Entomological Institute 79: 580 pp.
Jerath, M. L. 1960. Notes on larvae of nine genera of Aphodiinae in the United States. Proceedings of the United States National Museum, Washington 111(3425): 43-94.
Krell, F.-T. 2000. The fossil record of Mesozoic and Tertiary Scarabaeoidea (Coleoptera: Polyphaga). Invertebrate Taxonomy 14: 871-905.
Krell, F.-T. 2006. Fossil record and evolution of Scarabaeoidea (Coleoptera: Polyphaga). Coleopterists Society Monograph 5: 120-143.
Ritcher, P.O. 1966. White grubs and their allies: A study of North American scarabaeoid larvae. Oregon State University Press, Corvallis, Oregon. Studies in Entomology 4: 219 pp.