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Family Passalidae - Bess Beetles

Horned Passalus For Illinois In August - Odontotaenius disjunctus Bess beetle - Odontotaenius disjunctus WVWVWV - Odontotaenius disjunctus Horned Passalus (Odontotaenius disjunctus) - Odontotaenius disjunctus beetle carrying arachnids - Odontotaenius disjunctus Unidentified Beetle - Odontotaenius disjunctus Odontotaenius disjunctus Patent-leather Beetle? - Odontotaenius disjunctus
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Coleoptera (Beetles)
Suborder Polyphaga
Superfamily Scarabaeoidea
Family Passalidae (Bess Beetles)
Other Common Names
Peg Beetles, Betsy Beetles, Patent Leather Beetles, Horn Beetles
Synonyms and other taxonomic changes
Passalidae Leach, 1815
Explanation of Names
Family name is from Greek passalos, meaning a peg or gag, originally bestowed by Fabricius (1).
"Bess" beetle would appear to be from French baiser, to kiss (compare Middle English bassen, Modern English, though archaic, buss to kiss), after the kissing sound (stridulation) made by the beetles when handled. "Betsy" would appear to be a variant of "bess". Betsy is a a form of the English name "Bess", short for the name Elizabeth, not related to the French "bess" in meaning, but this would appear to explain the progression baiser-->"Bess"-->"Betsy" (Internet searches).
"Peg" beetle is likely from the appearance of the beetle protruding from its excavation in a log, like a carpenter's peg.
Patent leather is a shiny leather, referring to the shiny body of these beetles.
"Horn Beetle" is one of several common names given by Blatchley (2) and presumably refers to the shiny body as well.
Two genera and four species in North America (Univ. Florida,
However, only two species, both in genus Odontotaenius, are currently known to occur in the United States--the other two species are doubtfully (or formerly?) known from Arizona (Schuster, 1994).
Worldwide, about 500 species are known (Schuster, 2001).

Tribe Proculini
Genus Odontotaenius Kuwert 1896
Odontotaenius disjunctus (Illiger 1800) - General, except far West
Odontotaenius floridanus Schuster 1994 - Florida
Tribe Passalini
Genus Passalus Fabricius 1792
Passalus interruptus (Linnaeus 1758) - AZ?
Passalus punctiger Serville 1825 - AZ?
30-40 mm
Large dark beetles with characteristic body form and lifestyle:
robust body, distinct gap between pronotum and elytra
pronotum grooved in middle
elytra deeply grooved
mandibles robust, toothed, project beyond tip of labrum
antennae not elbowed (geniculate) like those of the Lucanidae, but they are curved when relaxed
antennae have 10 segements, including a club of 3 (typically) to 6 segments
antennal plates (lamellae) cannot be pressed together as in Scarabaeidae and related families.
mentum (lower mouthpart) deeply notched, the notch occupied by the large, horn-like ligula, see Dillon, fig. 438 (3)
Each tarsus has five segments (tarsal formula 5-5-5)
Some images of the widespread Horned Passalus, Odontotaenius disjunctus, illustrating these characters:

Larvae no longer use the last pair of legs for walking; they are turned 90 degrees to rub against a rough patch of cuticle on the more anterior segment of the thorax. Using this "third pair of legs," the communicate with sound. This communication is between larvae and adults in passalid communities in decaying wood.(4)
Eastern and south-central North America. The Horned Passalus, Odontotaenius disjunctus is widespread in east. Odontotaenius floridanus is a Florida endemic, described in 1994. These are apparently the only two species of the family known to occur in North America (United States and Canada).
Family is cosmopolitan, with most species in the tropics.
Live inside rotting logs in forests.
Adults and larvae feed on wood
Life Cycle
Unusual (for beetles) subsocial lifestyle. Adults and larvae live together in family groups in galleries excavated in rotting wood by adults. Adults care for larvae, and actively feed them pre-chewed food. Both adults and larvae stridulate, which is used for communication within the group. See Generic Guide to New World Scarab Beetles for more details.
Adults communicate with larvae via squeaking sounds that are created by rasplike oval patches near the 5th abdominal segment. Fourteen distinct signals have been documented. The larvae respond by rapidly vibrating their stumpy, pawlike hind legs over patches of ridges at the base of the middle legs. These sounds are audible by humans. The may deter predators. Or it may keep adults and larvae near each other, since the larvae are dependent on the adults for food and symbiotic microorganisms that aid digestion. (5)
See Also
Stag Beetles--Lucanidae
Scarab Beetles--Scarabaeidae
Print References
Arnett et al., America Beetles, Vol. 2, Chapter 25 (6)
Blatchley, p. 908 (2) (link)
The Century Dictionary--entry for passalus (1)
Dillon and Dillon (3)
Gordh, p. 670 (7)
Schuster, 1994. Odontotaenius floridanus New Species (Coleoptera: Passalidae): A Second U.S. Passalid Beetle. Florida Entomologist 77(4): 474-478, available here.
Works Cited
1.The Century Dictionary: an encyclopedic lexicon of the English language
2.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.
3.A Manual of Common Beetles of Eastern North America
Dillon, Elizabeth S., and Dillon, Lawrence. 1961. Row, Peterson, and Company.
4.Hidden Company that Trees Keep: Life from Treetops to Root Tips
James B. Nardi. 2023. Princeton University Press.
5.The Lives of Beetles: A Natural History of Coleoptera
Arthur V. Evans. 2023. Princeton University Press.
6.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.
7.A Dictionary of Entomology
George Gordh, David H. Headrick. 2003. CABI Publishing.