GEOTRUPIDAE | uk beetles

POLYPHAGA Emery, 1886

SCARABAEIODEA Latreille, 1802

7-26mm

GEOTRUPIDAE Latreille, 1802

Dor Beetles

These large beetles are spread across the UK, and can be found in almost any habitat where large mammals are present. This group includes some of our most impressive dung beetles.

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Around the World

This is a large and almost cosmopolitan family of about 70 genera and more than 600 species included, generally, in 3 subfamilies. The greatest diversity occurs in the tropical regions and the various groups tend to be regionally partitioned; the Geotrupinae is mostly Holarctic whereas the Bolboceratinae is mostly tropical. The Bolboceratinae contains 2 tribes; the Bolboceratini is very diverse and widespread throughout Australia, Africa and South America while the Athyreini is mostly Neotropical. The Geotrupinae contains 2 very distinct tribes; the Ceratotrupini includes most of our familiar species and is mostly Palaearctic and Asian, extending to North Africa and in the Nearctic from Canada to Central America. The Lethrini includes a single speciose genus, Lethrus Scopoli, 1777, which is Palaearctic with the widest diversity in Central Asia. The common name of 'Earth-boring Dung Beetles' refers to their habit of burrowing, which is reflected in the family name; this is derived from the Greek for earth, geos, and borer, trypetes. The more commonly used name 'Dor Beetles' is an English invention.

The classification of the family has been in flux for many years and is by no means settled; it was originally included as a subfamily of the scarabaeidae, and there is much evidence that the group is not monophyletic, and that the ranking, or even the inclusion in the case of e.g. the Taurocerastinae, is still being worked out. Though maybe simplistically, the Geotrupidae has been separated from other scarabaeiod groups by, among other things, the 11-segmented antennae. Plecoma LeConte, 1856 is a genus of about 35 species of Nearctic burying beetles much like geotrupids, they are called ‘rain beetles’ from their habit of appearing after autumn and winter rains and they superficially resemble geotrupids but for the very long and dense pubescence on the underside, the antennae are 11-segmented but with a 3-6 segmented club and the pro-coxal cavities are open whereas in the geotrupids they are closed. The genus is now variously considered to form its own family, the Plecomidae LeConte, 1861, but formerly it has variously been considered to be a subfamily of both the Geotrupidae and the Scarabaeidae.

Description

They are of a characteristic oval and very convex appearance although in tropical regions sexual dimorphism can be spectacularly developed with the males looking, at first glance, very atypical e.g. see Ceratophyus polyceros Pallas, 1771 or Enoplotrupes sharpi Rothschild & Jordan, 1893, and some truly bizarre examples can be seen in the Australian genera Blackburnium Boucomont, 1911 and Bolborhachium Boucomont, 1911. Most are medium sized beetles but this varies widely; the smallest at around 5mm is represented by the European Odonteus Samouelle, 1819 , while tropical species may reach 50mm e.g. Enoplotrupes Lucas, 1869 species. Most species are glabrous dorsally and pubescent below, sometimes densely so, and most have numerous strong setae on the head, especially around the mouthparts, and at the base of the antennae and the tibiae and tarsi, especially the meso- and metatibiae. Palaearctic species tend to be drab; black to pale brown and variously metallic, but in tropical regions there are many

Enoplotrupes sharpi Jordan & Rothschild, 1893

bright metallic and vividly coloured genera e.g. the Asian Bolbochromus Boucomont, 1909 or the Australian Bolborhachium Boucomont, 1911. Head and pronotum variously punctured, sometimes densely so, although often almost impunctate, and the elytra tend to be smooth or only micropunctured. The head is prognathous, never deflexed, with robust and prominent mandibles which project beyond the labrum; in some genera they display dimorphism e.g. Lethrus Scopoli, 1777. The antennae are 11-segmented, which separates the Geotrupids from most other scarabaeiod groups, with a 3-segmented club. Eyes usually large and prominent and completely, or at least partially, divided by a canthus which may be expanded laterally and so be visible from above. Clypeus often dimorphic, generally truncate and produced in front of the clypeus. Maxillary palps 4-segmented, labial palps 4-segmented except in the Lethrini where they are 3-segmented. Pronotum convex; wider than or equal in width to the elytral base, often modified and sometimes greatly so in the male. Elytra convex and entire, completely covering the abdomen and sometimes shorter than the pronotum e.g. in the Lethrini, variously striate; from smooth and lacking striae to having deep and strongly punctured striae which are as wide as the interstices. The lateral margins are often to some extent explanate. Scutellum usually large, triangular or cordate. Legs robust, sometimes very much so, and adapted for digging; coxae transverse; the mesocoxae sometimes contiguous; protibiae toothed externally, sometimes very strongly so, and with a large apical spur which may be dimorphic, meso- and metatibiae with strong transverse ridges along the outer face and 2 strong and adjacent apical spurs. Tarsi 5-5-5, claws equal and simple, without a basal tooth, and usually robust, a bisetose empodium extends beyond the apical segment and is usually obvious. Abdomen with 6 free sternites. Wings almost always very well developed. Both the larvae and adults of most species stridulate. The larvae resemble those of the Scarabaeidae; C-shaped, soft-bodied and creamy or yellow in colour with a dark and well sclerotized head.

Ecology

The biology of the family is diverse although that of many species remains unknown; some adults do not feed but most species are coprophagous, mycetophagous or saprophagous and they generally pass most of their lives in burrows and so are seldom seen. Adults provision the burrows with food for the larvae, typically dung, vegetation, compost or fungi, but beyond this they display no parental care. In warmer regions there may be overlapping generations so that adults are present virtually year round; in some species e.g. various Bolboceras Kirby, 1819 the burrows have been found to contain adults, pupae, larvae and eggs simultaneously. In temperate regions the adults tend to overwinter in burrows and become active in the spring, with new generation adults in the autumn, so that there are 2 peaks of activity. Most species dig deep, vertical burrows (generally 15-200cm deep but burrows down to 3 metres have been recorded) which may be straight or branched; eggs are sometimes laid in the soil in side chambers or among the provisions directly and fecundity is known to be low in many species. Most species are common or abundant where they occur, and some dung feeders may swarm in large numbers, a reflection of the ephemeral nature of the food-source and of the competition, while some are solitary and others are semi-colonial. Most species are crepuscular or nocturnal and many are attracted to light although in temperate regions the adults also tend to be active in hot sunshine, and many will be found to be infested with phoretic mites. Some species are attracted to fermenting vegetation.

A key to the British species can be found HERE.