Passalidae is a family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of beetle

Beetle

Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...

s known variously as "bessbugs", "bess beetles", "betsy beetles" or "horned passalus beetles". Nearly all of the 500-odd species are tropical; species found in North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 are notable for their size, ranging from 20–43 mm, for having a single "horn" on the head, and for a form of social behavior

Social behavior

In physics, physiology and sociology, social behavior is behavior directed towards society, or taking place between, members of the same species. Behavior such as predation which involves members of different species is not social...

 unusual among beetles.

Bodies elongate-cylindrical and black overall; ventral surfaces may be covered with yellow setae.