Overview
The Bess Beetle family is most diverse in tropical regions. Members of this
family are typically large beetles (20 to 70 mm long) with a sublamellate
antennal club. The form of body (elongate and dorsoventrally depressed) and
form of the mentum (deeply emarginate apically) help to distinguish this family
from other scarabaeoids. Adults and larvae live together in subsocial groups
in rotting logs.
Description
Length 15.0-70.0 mm. Shape elongate-cylindrical and depressed. Color black
(tenerals orange to deep maroon); ventral surface with or without erect, moderately
dense, yellow setae. Head prognathus, narrower than thorax, often with dorsomedian
horn. Antennae 10-segmented, with 3-segmented club that is not opposable and
not geniculate (but is capable of being rolled together); segments of club
tomentose; antennae inserted under a prominent frontal margin. Eyes divided
in half by canthus, with exocone ommatidium. Clypeus reduced, separated from
frons by suture, or vertical and hidden beneath frons. Labrum distinct, prominent,
projecting beyond apex of front of head, clypeal apex deeply emarginate, bisinuate,
or truncate. Mandibles projecting beyond apex of labrum, large, curved, toothed,
blunt. Maxillae with 4-segmented palpi; galea with apical hook; submentum
large, prominent; mentum large, emarginate at apex; labium with 3-segmented
palpi. Pronotum broader than head, quadrate, surface smooth with median, longitudinal
groove. Elytra elongate, sides parallel, apices rounded, with striae well
developed. Pygidium concealed by elytra. Scutellum triangular, small (exposed
only in groove between pronotum and elytra). Legs with transverse coxae, mesocoxae
closed; protibiae with several external teeth on outer margin, apex with 1
spur; meso- and metatibiae with ridges, apices with 2 spurs; spurs mesad,
adjacent (not separated by basal metatarsal segment); tarsal formula 5-5-5;
claws equal in size, simple; empodium present, not extending beyond fifth
tarsal segment, with 2 setae. Abdomen with 5 visible sternites; 7 functional
abdominal spiracles situated in pleural membrane. Wings well developed without
M-Cu loop, with 1 apical detached vein. Male genitalia trilobed. Female genitalia
with paraprocts, proctiger, and styli absent; valvifers and coxite present.
References: Scholtz 1990; Sharp and Muir 1912; Tanner 1927.
Classification Status
Taxonomy of the species in the United States, Mexico and Central America is
well known, although new species are still being found. Taxonomy of passalids
in other regions of the world needs further study. Monophyly of the family
is supported by larval and adult characteristics (see Scholtz 1990; Browne
and Scholtz 1995). According to the phylogenetic analysis of Browne (1993),
the Passalidae is the basal member of a clade that includes the Diphyllostomatidae,
Lucanidae, Glaphyridae, Trogidae, Bolboceratinae (Geotrupidae), and Pleocomidae.
World catalog: Hincks and Dibb 1935. Keys to Nearctic genera: Reyes-Castillo
1970; Schuster 1983a. Keys to genera of larvae: Schuster 1992.
Distribution
There are over 500 described species, nearly all of which are tropical. A
fossil passalid beetle, Passalus indormitus Cockerell, is known from Oligocene
deposits of Oregon (Reyes-Castillo 1977). It is very similar to P. punctiger.
Ecology
Passalid adults live in well decayed logs and stumps with their larvae and
subsocial family groups. All stages are found in galleries in wood that are
excavated by the adults. Eggs are usually placed together in a "nest"
of frass. In many species, recently oviposited eggs are red; as they mature,
they change to brown, then to green. Adults and larvae communicate by stridulating
and can produce 14 different calls. Adults care for larvae and prepare food
by chewing it and presumably mixing it with saliva. Both adults and larvae
need to feed on adult feces that are predigested by microflora (essentially
an external rumen). Biology: Reyes-Castillo 1970; Reyes-Castillo and Halffter
1984; Schuster 1975a, 1975b, 1983b; Gray 1946; Schuster and Schuster 1997;
Ratcliffe 1991.
Larvae
Form elongate, subcylindrical, slightly curved (not c-shaped). Color creamy
white or blue-white (except at caudal end which may be darkened by accumulated
feces). Cranium lightly sclerotized. Antennae 2-segmented with protruding
fleshy base, short. Lateral ocelli lacking. Frontoclypeal suture distinct.
Labrum rounded, setiferous at apex; maxilla with galea and lacinia distinctly
separate, stridulatory area present, palpi 2-segmented (apparently 3-segmented).
Abdominal segments without annuli. Spiracles cribriform with C-shaped peritremes.
Venter of last abdominal segment with 2 anal lobes. Pro- and mesothoracic
legs 4-segmented, with long, curved claw; metathoracic leg unsegmented, reduced
to a stub with several apical teeth that rub against stridulatory area on
coxa of mesothoracic leg. References: Böving and Craighead 1930-1931;
Krause and Ryan 1953; Ritcher 1966; Scholtz 1990. Keys to larvae: Schuster
1992; Schuster and Reyes-Castillo 1981.
References Cited
BROWNE, D. J. 1993. Phylogenetic significance of the hind
wing basal articulation of the Scarabaeoidea (Coleoptera). Ph.D. Thesis, University
of Pretoria, Pretoria, South Africa.
BROWNE, D. J. and C. H. SCHOLTZ. 1995. Phylogeny of the families
of the Scarabaeiodea (Coleoptera) based on characters of the hindwing articulation,
hindwing base and wing venation. Systematic Entomology 21: 145-173.
BOVING, A.
G. and F. C. CRAIGHEAD. 1930-1931. An illustrated synopsis of the
principal larval forms of the Coleoptera. Reprint edition, Brooklyn Entomological
Society, Merrick, NY. 351 pp.
GRAY, I. E. 1946. Observations on the life history of the
horned Passalus. American Midlands Naturalist 35: 728-746.
HINCKS, W. D. and J. R. DIBB. 1935. Passalidae, Coleopterorum
Catalogus pars 142: 1-118.
KRAUSE, J. B. and M. T. RYAN. 1953. Annals of the Entomological
Society of America. 47: 1-20, 4 pls.
RATCLIFFE, B. C. 1991. The Lucanidae and Passalidae (Insecta:
Coleoptera) of Nebraska. Great Plains Research 1: 249-282.
REYES-CASTILLO, P. 1970. Coleoptera: Passalidae; morfologia y division en grandes grupos; generos americanos. Folia Entomologica Mexicana 20-22: 1-240.
REYES-CASTILLO,
P. 1977. Systematic interpretation of the Oligocene fossil Passalus
indormitus (Coleoptera: Passalidae). Annals of the Entomological Society
of America 70: 652-654.
REYES-CASTILLO, P. and G. HALFFTER. 1984. La estructura social
de los Passalidae (Coleoptera: Lamellicornia). Folia Entomologica Mexicana
61: 49-72.
RITCHER, P. O. 1966. White Grubs and their Allies. Oregon
State University Press, Corvallis, OR.
SCHOLTZ, C. H. 1990. Phylogenetic trends in the Scarabaeoidea
(Coleoptera). Journal of Natural History 24: 1027-1066.
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: 302-305.
SCHUSTER, J. C. 1983b. Acoustical signals of passalid beetles:
complex repertoires. Florida Entomologist 66: 486-496.
SCHUSTER, J. C. 1992. Passalidae: state of larval taxonomy
with description of New World species. Florida Entomologist 75: 358-369.
SCHUSTER, J. C. and P. REYES-CASTILLO. 1981. New World genera of
Passalidae (Coleoptera): a revision of larvae. Anales de la Escuela Nacional
de Ciencias Biologicas, Mexico 25: 79-116.
SCHUSTER, J. C., and L. B. SCHUSTER. 1997. The evolution
of social behavior in Passalidae, 260-269 p. In Choe, J. and Crespi, B. (eds.),
The Evolution of Social Behavior in Insects and Arachnids. Cambridge University
Press, Cambridge.
SHARP, D. and F. MUIR, F. 1912. The comparative anatomy of
the male genital tube in Coleoptera. Transactions of the Entomological Society
of London 1912: 477-642.
TANNER, V. M. 1927. The female genitalia of Coleoptera. Transactions
of the American Entomological Society 53: 3-50.