Geotrupidae

Dor beetle Geotrupes stercorarius, copyright Jessica Towne.

Belongs within: Scarabaeoidea.
Contains: Bolboceratinae.

The Geotrupidae are a group of scarabaeoid beetles which typically dig burrows that they provision with dung, dead leaves or humus (Jameson 2002). They are generally characterised by an eleven-segmented antenna bearing a club of three circular or oval antennomeres.

Opening dors
Published 21 May 2022

My current dayjob mostly revolves around identifying and counting dung beetles. When Europeans settled Australia, they brought their farm animals with them. Unfortunately, the large piles of dung produced by cattle and horses proved rather daunting to native scavengers used to the more compact droppings of kangaroos and possums. And if you’ve ever experienced an Australian summer, you’ll know that flies are definitely a thing. To help with this situation, Australia has had a long-running programme introducing exotic dung beetles that are better able to clean up after livestock. Most of these are members of the typical dung beetle family Scarabaeidae but one species, Geotrupes spiniger, represents a different subgroup of the superfamily Scarabaeoidea. These are the earth-boring dung beetles or dor beetles of the Geotrupidae.

Dor beetle Geotrupes spiniger, copyright Udo Schmidt.

The geotrupids are medium-sized to very large beetles, ranging in size from half a centimetre to 4.5 cm in length (Jameson 2002). Like many other members of the Scarabaeoidea, they have broad fore legs used for digging. Their short, eleven-segmented antennae end in the asymmetrical club typical of scarabaeoids but they may be distinguished from other families in that the basal segment of the three-segmented club is expanded to form a ‘cup’ against which the other segments may be tightly closed. The body of geotrupids is strongly convex, and is smooth and shiny dorsally but hairy underneath. In many species, the males may bear elaborate horns and/or processes on the head and pronotum.

Male Taurocerastes patagonicus, copyright Nicolás Lavandero.

Despite their size, geotrupids are secretive animals, spending most of their time in burrows underground (which may be up to three metres in depth) and usually only emerging at night. Various species feed on animal dung or decaying matter; some feed on subterranean fungi. In at least some species, eggs are laid in brood chambers within the parent’s home burrow and multiple life stages may share a single burrow. Burrows may also be shared between multiple adults when conditions demand. Though adults do not directly tend to larvae, they may stock brood chambers with food supplies. In some Australian species of the subfamily Bolboceratinae, females lay a single gigantic egg at a time that may be up to 56% the size of its layer (Houston 2011). Larvae hatching from such an egg are able to develop right through to maturity without feeding.

Adult geotrupids produce a stridulating noise when disturbed which is the origin of the alternate vernacular name of “dor beetle” (“dor” being an old word for a buzzing insect). Larvae may or may not be capable of stridulation, depending on the species.

Male Blackburnium rhinoceros, copyright Edward Bell.

The classification of geotrupids is the subject of ongoing investigation. A recent classification divides the family between three subfamilies, the widespread Geotrupinae and Bolboceratinae and the South American Taurocerastinae. Morphological differences between these subfamilies, particularly at the larval stage, have lead some researchers to question whether the Geotrupidae in the broad sense represents a monophyletic group. Molecular analyses thus far seem ambiguous; an analysis by McKenna et al. (2015) placed geotrupids as part of a polytomy near the base of the scarabaeoids. As an aside, my supervisor recently asked myself and a retired colleague whether Geotrupes spiniger was the only species of geotrupid found in Australia. I replied “yes”, our colleague responded “no”. Our conflict, of course, was based on whether Australia’s wide diversity of Bolboceratinae contributed to the count.

Systematics of Geotrupidae

Characters (from Jameson 2002): Length 5–45 mm. Shape oval or round. Colour yellowish, brown, orange-brown, reddish-brown, purple, brown, or black (with or without metallic reflections). Head not deflexed. Antennae eleven-segmented with three-segmented, opposable club (all antennomeres tomentose). Eyes with eucone or exocone ommatidia, completely or partially divided by canthus. Clypeus often with tubercle or horn. Labrum truncate, prominent, produced beyond apex of  clypeus. Mandibles produced beyond apex of labrum, prominent. Maxillae with four-segmented palpi; labium with three- or four-segmented palpi. Pronotum convex with base wider than or subequal to elytral base and with or without tubercles, ridges, horns, or sulci. Elytra convex, with or without striae. Pygidium concealed by elytra. Scutellum exposed, triangular. Legs with coxae transverse, mesocoxae separated or contiguous; protibiae serrate on outer margin, apex with one spur; meso- and metatibia with ridges, apex with two spurs; tarsi 5-5-5; claws equal in size, simple; empodium present, extending beyond fifth tarsomere, with two setae. Abdomen with six free sternites; seven functional abdominal spiracles situated in pleural membrane (spiracles 1–7) and vestigial spiracle in pleural membrane (spiracle 8) or with eight functional spiracles situated in the pleural membrane (spiracles 1–7) and the eighth pair in the tergite. Wings well developed, M-Cu loop and two apical detached veins present. Male genitalia variable. Larvae scarabaeiform (C-shaped, cylindrical). Colour creamy-white or yellow (except at caudal end which may be darkened by accumulated feces). Cranium heavily sclerotised, brown to dark brown. Antennae three-segmented, penultimate segment bearing one or more distal sense organs, last segment reduced in diameter. Lateral ocelli absent. Frontoclypeal suture absent or present. Labrum at apex with three weak lobes or rounded. Epipharynx in most trilobed with symmetrical tormae. Maxilla with galea and lacinia distinctly separate; maxillary stridulatory area with teeth; maxillary palpi four-segmented. Abdominal segments 3 to 7 with two annuli, each with one or more transverse rows of short setae. Spiracles cribriform or biforous. Venter of  last abdominal segment V-shaped or Y-shaped, surrounded by fleshy lobes in some taxa. Legs four-segmented or pro- and mesothoracic legs three-segmented and metathoracic leg reduced in size and two-segmented; stridulatory apparatus on meso- and metathoracic legs present or absent; claws absent or present.

<==Geotrupidae [Geotrupides]
    |  i. s.: Anaplotrupes stercorosus (Scriba 1791)A06
    |         Ceratophyus Fischer von Waldheim 1823J02
    |           `--C. gopherinusJ02
    |         Mycotrupes LeConte 1866J02
    |           `--M. gaigeiKR91
    |         Peltotrupes Blanchard 1888J02
    |           |--P. profundusJ02
    |           `--P. youngiJ02
    |--+--Taurocerastinae [Taurocerastini]MW15
    |  |    |--Taurocerastes patagonicus Philippi 1866MF15, B14
    |  |    `--FrickiusB14
    |  `--+--BolboceratinaeMF15
    |     `--Pleocominae [Pleocomidae]MW15
    |          |--Crecotoma Nikolajev 2002 [Cretocomini]N02
    |          |    `--*C. tologoica Nikolajev 2002N02
    |          `--Pleocoma Le Conte 1856MF15, N02 [Pleocomini]
    |               |--P. australis Fall 1911B14
    |               `--P. fimbriataH02
    `--GeotrupinaeMF15
         |--Lethrus [Lethrinae, Lethrini]MF15
         |    |--L. apterus (Laxmann 1770)B14
         |    |--L. cephalotesL02
         |    `--L. geminatusMF15
         `--Geotrupes Latreille 1796MF15, CW92 [Geotrupini]
              |  i. s.: G. autumnalisR26
              |         G. bicornisR26
              |         G. impressusC01
              |         G. mutatorC01
              |         G. spiniger Marsham 1802CW92
              |         G. splendidus (Fabricius 1775)B14
              |         G. sylvaticusC01
              |         G. typhaeusR26
              |         G. vernalis (Linnaeus 1758)L02, L58 [=Scarabaeus vernalisL02]
              |--*G. (Geotrupes) stercorarius (Linnaeus 1758) [=Scarabaeus stercorarius]CW92
              |--G. (Anoplotrupes Jekel 1865)J02
              |--G. (Cnemotrupes Jekel 1865) [incl. Onychotrupes Jekel 1865]J02
              |--G. (Geohowdenius Zunino 1984)J02
              `--G. (Megatrupes Zunino 1984)J02

*Type species of generic name indicated

References

[A06] Ahrens, D. 2006. The phylogeny of Sericini and their position within the Scarabaeidae based on morphological characters (Coleoptera: Scarabaeidae). Systematic Entomology 31: 113–144.

[B14] Bouchard, P. (ed.) 2014. The Book of Beetles: A lifesize guide to six hundred of nature’s gems. Ivy Press: Lewes (United Kingdom).

[CW92] Cassis, G., & T. A. Weir. 1992. Geotrupidae. In: Houston, W. W. K. (ed.) Zoological Catalogue of Australia vol. 9. Coleoptera: Scarabaeoidea pp. 41–64. AGPS Press: Canberra.

[C01] Csiki, E. 1901. Bogarak [Coleopteren]. In: Horváth, G. (ed.) Zichy Jenő Gróf Harmadik Ázsiai Utazása [Dritte Asiatische Forschungsreise des Grafen Eugen Zichy] vol. 2. Zichy Jenő Gróf Harmadik Ázsiai Utazásának Állattani Eredményei [Zoologische Ergebnisse der Dritten Asiatischen Forschungsreise des Grafen Eugen Zichy] pp. 75–120. Victor Hornyánszky: Budapest, and Karl W. Hierseman: Leipzig.

Houston, T. F. 2011. Egg gigantism in some Australian earth-borer beetles (Coleoptera: Geotrupidae: Bolboceratinae) and its apparent association with reduction or elimination of larval feeding. Australian Journal of Entomology 50: 164–173.

[H02] Hovore, F. T. 2002. Pleocomidae LeConte 1861. In: Arnett, R. H., Jr, M. C. Thomas, P. E. Skelley & J. H. Frank (eds) American Beetles vol. 2. Polyphaga: Scarabaeoidea through Curculionoidea pp. 20–22. CRC Press.

[J02] Jameson, M. L. 2002. Geotrupidae Latreille 1802. In: Arnett, R. H., Jr, M. C. Thomas, P. E. Skelley & J. H. Frank (eds) American Beetles vol. 2. Polyphaga: Scarabaeoidea through Curculionoidea pp. 23–27. CRC Press.

[KR91] Krantz, G. W., L. A. Royce, R. R. Lowry & R. Kelsey. 1991. Mechanisms of phoretic specificity in Macrocheles (Acari: Macrochelidae). In: Dusbábek, F., & V. Bukva (eds) Modern Acarology: Proceedings of the VIII International Congress of Acarology, held in České Budĕjovice, Czechoslovakia, 6–11 August 1990 vol. 2 pp. 561–569. SPB Academic Publishing: The Hague.

[L02] Latreille, P. A. 1802. Histoire Naturelle, générale et particulière des crustacés et des insectes vol. 3. Familles naturelles des genres. F. Dufart: Paris.

[L58] Linnaeus, C. 1758. Systema Naturae per Regna Tria Naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. Laurentii Salvii: Holmiae.

[MF15] McKenna, D. D., B. D. Farrell, M. S. Caterino, C. W. Farnum, D. C. Hawks, D. R. Maddison, A. E. Seago, A. E. Z. Short, A. F. Newton & M. K. Thayer. 2015. Phylogeny and evolution of Staphyliniformia and Scarabaeiformia: forest litter as a stepping stone for diversification of nonphytophagous beetles. Systematic Entomology 40: 35–60.

[MW15] McKenna, D. D., A. L. Wild, K. Kanda, C. L. Bellamy, R. G. Beutel, M. S. Caterino, C. W. Farnum, D. C. Hawks, M. A. Ivie, M. L. Jameson, R. A. B. Leschen, A. E. Marvaldi, J. V. McHugh, A. F. Newton, J. A. Robertson, M. K. Thayer, M. F. Whiting, J. F. Lawrence, A. Ślipiński, D. R. Maddison & B. D. Farrell. 2015. The beetle tree of life reveals that Coleoptera survived end-Permian mass extinction to diversify during the Cretaceous terrestrial revolution. Systematic Entomology 40 (4): 835–880.

[N02] Nikolajev, G. V. 2002. To possible assignment of a new genus of lamellicorn beetles from the Lower Cretaceous of Mongolia to the subfamily Pleocominae (Coleoptera, Scarabaeidae). Paleontologicheskii Zhurnal 2002 (3): 51–55 (translated: Paleontological Journal 36 (3): 279–282).

[R26] Risso, A. 1826. Histoire naturelle des principales productions de l’Europe méridionale et particulièrement de celles des environs de Nice et des Alpes maritimes vol. 5. F.-G. Levrault: Paris.

 

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