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For Insects, Spiders & Their Kin
For the United States & Canada

Species Odontotaenius disjunctus - Horned Passalus

Odontotaenius disjunctus (Illiger) - Odontotaenius disjunctus Large Black Beetle - Odontotaenius disjunctus Handsome fellow near Leesburg, Va. - Odontotaenius disjunctus Horned Passalus - Odontotaenius disjunctus Bess Beetle - Odontotaenius disjunctus Odontotaenius disjunctus Horned Passalus - Odontotaenius disjunctus Odontotaenius disjunctus? - Odontotaenius disjunctus
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Coleoptera (Beetles)
Suborder Polyphaga (Water, Rove, Scarab, Long-horned, Leaf and Snout Beetles)
Superfamily Scarabaeoidea (Scarab, Stag and Bess Beetles)
Family Passalidae (Bess Beetles)
Genus Odontotaenius
Species disjunctus (Horned Passalus)
Other Common Names
Bess Beetle, Bess Bug, Betsy Beetle or Bug, Patent Leather Beetle, Peg Beetle
Synonyms and other taxonomic changes
Odontotaenius disjunctus (Illiger)
Orig. Comb: Passalus disjunctus Illiger, 1800
Syn: Popilius disjunctus (Illiger) in much of the older literature.
Syn: Passalus cornutus Fabricius 1801
Explanation of Names
disjunctus likely refers to the jointed body.
Horned Passalus is the common name listed by the Entomological Society of America.
Bess Bug is a name in common use by non-entomologists. This is likely an imitation of the stridulation (Merriam-Webster). Speculation: "Bess" perhaps comes from French baiser, "to kiss" (compare English buss, kiss), and likely refers to the ability of this beetle to pinch with its mandibles (which it does rarely) or the sound of the stridulation--a squeaky "kissy" sound.
See family account for more on common names.
2 spp. n. of Mex. (1) (2nd sp. endemic to FL)
32-36 mm
Unique in its range: elongate shape, large size, deeply striated elytra. Larvae are scarabaeiform (Passalidae page at Univ. Florida), and appear to have only four legs. Hind legs are shortened, used for stridulation, communication with adults, presumably.
See also characteristics given for family.
Larvae only have two pairs of thoracic legs
TX-FL-QC-NE / Mex. to S. Amer. (2)(3)
Deciduous forests with rotting, fallen logs.
Can be found all year in rotting logs. Come to lights in spring and summer (see life cycle)
Decaying wood and/or fungi.
Life Cycle
Lifestyle of this family is unique for beetles: live in small colonies where larvae are cared for by adults of both sexes. Long life cycle, apparently more than one year. Larvae eat a rotting wood pre-chewed by adults. (Some references state larvae eat feces of adults as well.) Larvae and adults also cannibalize injured larvae.
Adults reported to fly very seldom, however they are capable of flight, contrary to statements in some sources. Adults are found at lights on occasion. They may disperse by walking, but have been observed flying under lights (image), and they are sometimes taken in light traps (MacGown and MacGown, 1996). A nuptial flight has been observed in Mississippi, with a group of 12-15 individuals flying at dusk, and one pair even mating in flight (MacGown and MacGown, 1996). Mating is also observed in the tunnels, the copulation occurring, characteristically as shown:
Both adults and larvae stridulate, and this is said to serve as communication between them. Adults also stridulate when picked up, and especially, blown on. Adults stridulate by rubbing abdomen against the wings. Larvae stridulate with reduced third pair of legs--these scratch against other legs.
Illustration of larva, pupa, and adult:
Print References
Blatchley, p. 908, fig. 358--larva, pupa, adult (4) (link)
Brimley, p. 367 states that Zelia vertebrata parasitizes this beetle. Brimley, p. 209, lists the beetle for the "whole year" throughout the state of North Carolina, in decaying hardwood logs (5)
Downie and Arnett, p. 632 (2)
Gray, I.E. 1946. Observations on the Life History of the Horned Passalus. American Midland Naturalist, 35(3): 728-746.
MacGown, J. and M. MacGown. 1996. Observation of a nuptial flight of the horned Passalus beetle, Odontotaenius disjunctus (Illiger) (Coleoptera: Passalidae). The Coleopterists Bulletin 50: 201-203 (quoted here, PDF).
Schuster, J.C. 1975a. A comparative study of copulation in Passalidae (Coleoptera): New positions for beetles. Coleopterists Bulletin 29: 75-81.
Schuster, J.C. 1975b. Comparative behavior, acoustical signals and ecology of New World Passalidae (Coleoptera). Ph.D. Thesis. University of Florida. 127 pp.
Schuster, J.C. 1983a. The Passalidae of the United States. Coleopterists Bulletin 37(4): 302-305.
Schuster, J.C. 1983b. Acoustical signals of passalid beetles: complex repertoires. Florida Entomologist 66: 486-496.
Schuster, J.C. 1984. Passalid beetle (Coleoptera: Passalidae) inhabitants of leaf-cutter ant (Hymenoptera: Formicidae) detritus. Florida Entomologist, 67: 175-176.
Works Cited
1.American Beetles, Volume II: Polyphaga: Scarabaeoidea through Curculionoidea
Arnett, R.H., Jr., M. C. Thomas, P. E. Skelley and J. H. Frank. (eds.). 2002. CRC Press LLC, Boca Raton, FL.
2.The Beetles of Northeastern North America, Vol. 1 and 2.
Downie, N.M., and R.H. Arnett. 1996. The Sandhill Crane Press, Gainesville, FL.
3.The Scarabaeoid Beetles of Nebraska
Brett C. Ratcliffe & M.J. Paulsen. 2008. University of Nebraska State Museum, Vol 22, 570 pp.
4.An illustrated descriptive catalogue of the Coleoptera or beetles (exclusive of the Rhynchophora) known to occur in Indiana.
Blatchley, W. S. 1910. Indianapolis,Nature Pub. Co.
5.Insects of North Carolina
C.S. Brimley. 1938. North Carolina Department of Agriculture.