SCARABAEIDAE Latreille, 1802
Scarab Beetles
Includes about 70 dung beetle species, of which many are common and widespread. Of our 20 or so chafers several will be found in the warmer months both by day and by night.
POLYPHAGA Emery, 1886
SCARABAEIODEA Latreille, 1802
6
26
Approx. 90
2.5-35mm
Suborder:
Superfamily:
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Genera:
Species:
Size:
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Introduction
This large and cosmopolitan family includes about 30000 described species in 17 subfamilies and numerous tribes and genera but the classification is not stable and the faunas of many areas, especially in the tropics where most of the groups are very speciose, are only poorly understood. The Geotrupidae, Trogidae and Glaphyridae were formerly included as subfamilies. As presently defined the group includes a significant and conspicuous element of the fauna of most regions, adults are often large and brilliantly coloured, widespread and common, and easily sampled and so are popular with collectors and as pets or ornamental displays. Life histories are diverse and interesting and those of many species are available in the literature but further and often surprising adaptive strategies are constantly being discovered and so the group is also popular with researchers. The vast majority are generally known as dung beetles or chafers , terms which tend to conceal their amazing diversity, but the group also includes the Dynastinae MacLeay, 1819, the so-called Rhinoceros and Hercules beetles etc. which are among the largest and heaviest of all insects; the African Goliathus goliathus (Drury, 1770) is one of the heaviest at up to 100 grams, and the Neotropical Elephant beetle, Megasoma elephas Fabricius, 1775, and Hercules beetle, Dynastes hercules (Linnaeus, 1758) are both among the largest. Dynastinae in particular, but dung beetles in general, are also fascinating for their sexual dimorphism which may be extreme and is usually the result of sexual selection.
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The classification of various groups is well-established and generally acknowledged, especially where these are speciose in developed areas, but on a world-basis the limits of many groups are only poorly defined and most groups of chafers; Melolonthinae, Rutelinae and Cetoniinae, are so poorly understood taxonomically that in many tropical and subtropical areas species cannot be reliably placed. In some regions e.g. the Neotropics, the family is referred to as Melolonthidae Samouelle, 1819 and includes the chafers and some others as subfamilies; Melolonthinae Leach, 1819, Euchirinae Hope, 1840 (sometimes as a tribe of Melolonthinae),
Phaenomeridinae Erichson, 1847, Dynastinae, Cetoniinae Leach, 1815, Glaphyrinae MacLeay, 1819 and Systellopodinae Endroi, 1966, while Scarabaeidae includes the remainder of the Scarabaeoidea except for Lucanidae Latreille, 1804, Trogidae MacLeay, 1819 and Passalidae Leach, 1819. Many other systems will be found in the literature, especially going back to the nineteenth century, but here we refer to the group as outlined under Scarabaeoidea i.e. treating the family as a group that includes dung beetles, chafers and dynastines but excluding other families as listed. In the discussion that follows we will refer to frequently used synonyms etc. as necessary. A little more than 90% of all Scarabaeoidea are included in the present family i.e. about 30000, and of these the majority, about 22000 species, are chafers and rhinoceros beetles (etc.) while about 8000 are dung beetles i.e. Scarabaeinae and Aphodiinae Leach, 1815.
Ecology
Life-cycles and ecology among the species is widely diverse; very few are predators, see Canthonini, but otherwise the feeding habits and developmental media vary widely and it might be said that any decomposing organic matter is likely to host some species; many develop in herbivore dung and this has given rise to the name 'dung beetles' but they also inhabit and consume carrion, fungi, compost and vegetation generally including roots, foliage, fruits, nectar and pollen, some are myrmecophiles or termitophiles and many are associated with mammal and bird nests. Some dung beetles care for their eggs and/or larvae and some look after their food or brooding material, many fly well and are rapid to colonize fresh material as they follow herbivores etc. Adults of many chafers are diurnal and occur on flowers etc. while the majority of species generally are crepuscular or nocturnal, hiding during the day among foliage or within host material. Many species, including many large tropical dynastines, are attracted to light and may occur in huge numbers. Worldwide many chafers are horticultural or agricultural pests, with larvae consuming roots and adults attacking foliage e.g. the widely polyphagous Japanese Popellia japonica Newman, 1841 or the European Melolontha melolontha (Linnaeus, 1758) or Polyphylla fullo (Linnaeus, 1758), but chafers are also generally beneficial as pollinators. The biological effects of dung beetles are obvious both in removing dung from pasture and recycling nutrients to reducing the quantity of material available for other insects e.g. Diptera. Many species have been introduced into non-native areas to help reduce accumulating dung, and the classic example of this is from Australian pasture where the native species were not able to deal with the dung of introduced cattle species, many introduced from Africa readily utilized the cattle dung so clearing up the pasture and fertilizing the soil and increasing primary production. The term ‘dung beetle’ generally applies to members of the Aphodiinae and Scarabaeinae Latreille, 1802 although both groups include non-dung feeders and other families e.g. Geotrupidae Latreille, 1802 are also, quite rightly, referred to as such. Many species are generalists and will be found in the dung of a range of herbivores but many are specialists, occurring only in e.g. rabbit or deer pellets, and in general the dung of most animals will host one or the other. Three
Scarabaeus variolosus Fabricius, 1787
basic strategies are seen in dung beetles; those that collect dung, mould it, remove it from the source material and bury it so avoiding competition and desiccation e.g. Sisyphus Latreille, 1807 and Copris Geoffroy, 1762, those that work the dung and bury it directly beneath the pat e.g. Dialytes Harold, 1869 and Onthophagus Latreille, 1802, and those that utilize small pellets left out in the open, here the pellets form a hard, dry crust which preserves the internal moisture so allowing larval development. In general competition for dung is very strong, the rollers will often fight over a dung-ball and sometimes a ball is covered in males and females fighting for possession, and even during burial where one sex will stand guard while the other digs there will be constant attacks from others, even when the dung is within the burrow. Sometimes other ‘cuckoo’ species will enter a burrow, either directly or by digging an adjacent burrow, and attempt to requisition the dung for their own use. Those that bury dung beneath the pat, or develop directly within, need to out-compete rivals by consuming the dung and developing rapidly although in many cases the first female to arrive will produce chemicals which will deter other females from entering and ovipositing. Rabbit and deer pellets may often be found crammed with adult beetles or larvae of e.g. Aphodius Hellwig, 1798 or Onthophagus, usually to the point where it seems impossible for the dung to support their reproduction. With such intense competition most species develop rapidly, produce large populations readily and disperse quickly by flight and new host material is utilized soon after its arrival. Decaying fungi and vegetation will often host similar large numbers of scarabs, usually in fierce competition with many other species
of Coleoptera and Diptera etc. Those developing in avian and mammal nests occur throughout the world, many are generalists e.g. we have found Onthophagus joannae Goljan, 1953 swarming around the entrances of rabbit and badger burrows as well as occurring in great abundance in nearby deer pellets, but there are also many specialists and specific associations are common. Those developing within ant and termite nests tend to be highly specialized with their life-cycle intimately associated with the host. Chafers and dynastids feed on foliage and fruits as adults and upon compost, roots and decaying wood etc. as larvae but several tribes e.g. Valgini Mulsant, 1842 (Cetoniinae Leach, 1815) include termitophiles. The life cycle of many species is broadly similar with eggs deposited in organic host material or in the ground nearby, these hatch quickly and produce characteristic C-shaped larvae which develop quickly, although in many chafers this is prolonged over several seasons, passing through a small number of instars, often only two, and pupating in the ground or in a cell among the host material. In temperate regions adults may overwinter, or, rarely, remain active through the winter, or the pupal stage may overwinter and produce adults in the spring following further feeding. In general the adults will die off before the next generation eclose later in the year but there are many variations on this theme and some will be explored among the species accounts.
Description
Species vary widely in size from less than 2mm to about 160mm, many are massive as well as large and many males appear much larger due to exaggerated cephalic and pronotal development. The majority are between 3mm and 20mm with the dung beetles on average smaller than other groups. Habitus varies from elongate to quadrate, parallel-sided to strongly rounded, convex to dorsally flattened and continuous to strongly interrupted in outline. Pubescence is very variable; in general chafers are more pubescent then the other groups. Dung beetles tend to be drab although there are many brilliant metallic green or blue tropical species and temperate species e.g. of Onthophagus are often metallic to some extent, while chafers tend to be more gaudy, brightly coloured and metallic, tropical species more especially so, although nocturnal species e.g. of Melolontha Fabricius, 1775 and Amphimallon Latreille, 1825 tend to be drab. Dynastines are generally very distinctly coloured and patterned. All body sections are highly variable, the head varies from horizontal and produced to strongly deflexed, the morphology and range of sculpture is varies widely, even within some species, and the male may have strongly modified vertex and clypeal features as a result of sexual selection, the female may also display a (much narrower) range of variation of cephalic features. In general the dynastines and dung beetles display such dimorphism while the chafers do not. The antennae are 7-12 segmented but in the vast majority 10-segmented with an asymmetric and compact club which is articulated and versatile, as in many chafers, in chafers the club is usually glabrous towards the apex while in dung beetles it is pubescent throughout. Dung beetle antennae tend to be small while those of chafers
etc. tend to be larger and often dimorphic, being more developed in the male. The eyes are usually convex, entire and well-developed, especially in nocturnal species and many diurnal chafers, and in many dung beetles they are partly divided by a canthus. The mandibles are very variable but usually robust and well-sclerotized, rarely produced, exaggerated or obviously dimorphic, often hidden beneath the clypeus. The palpi are generally small and inconspicuous with cylindrical or fusiform segments, the labial palpi are 3-segmented and the maxillary palpi 4-segmented. Pronotum very variable; smooth, with or without tubercles, horns or otherwise sculptured, sometimes widely excavate anteriorly, variously bordered and impressed, smooth to variously microsculptured and punctured. Elytra transverse to elongate,
The Goliath Beetle (Cetoniinae)
Goliathus goliatus (Linnaeus, 1771)
convex to flattened, with or without striae or longitudinal carinae, often reflexed laterally and with well-developed epipleura and often covering the abdomen but many, especially among the chafers etc., with the pygidium and propygidium exposed. Scutellum exposed or hidden; variable in shape and convexity. Abdomen with 6 free sternites and 7 functional spiracles situated in pleural membranes (dung beetles) or in sternites, tergites or pleural membranes (chafers, dynastines etc.). Wings usually well-developed and most species are strong fliers, many chafers fly with the elytra closed. Legs usually robust and long, often fossorial; coxae transverse or conical, protibiae with a variable but small number of large external teeth or serrate along the external margin, generally with a single apical spur, rarely 2 e.g. in the New World genus Melanocanthus Halffter, 1958. Meso- and metatibiae slender to robust and variously toothed, with 1 or, usually, 2 apical spurs. Tarsi 5-segmented, generally small in dung beetles and larger in other groups, anterior tarsi missing in some Scarabaeinae. Claws variable; equal or unequal, simple to toothed or lobed, always free, in some chafers e.g. Hoplia Illiger, 1803, only a single claw. Empodium present, very variable; small to long and extending beyond the claws, without or with 2-5 terminal setae.
Larvae
The larvae are typically C-shaped and cylindrical, being referred to as ‘scarabaeiform’, although those of Sacarabaeinae tend to be hump-backed. Creamy white to yellow with a dark, well-sclerotized head. Antennae 4-segmented, the terminal segment with 1 or more sensory spots. Ocelli generally absent although present in some Cetoniinae and Dynastinae, in some species there are discreet ocelli-like dark spots. Frontoclypeal suture present, labrum variable from rounded to deeply emarginate. Abdomen with 10 segments or, in Cetoniinae, with 9 and 10 fused, segments 1-6 or 7 with 3 annuli and all with 1 or more transverse bands of setae. Spiracles cribriform, anal aperture transverse or, rarely, Y-shaped. Legs 2-segmented in Scarabaeinae, otherwise 4-segmented, without any stridulatory process. Claws present or absent.
Typical 'scarabaeiform' larva (Amphimallon solsticiale)
UK Subfamilies
AEGIALIINAE
Includes 3 species of Aegialia Latreille, 1807. All are associated with decaying vegetation on dry and sandy soils and all are vary local. A. arenaria (Fabricius, 1787) and A. rufa (Fabricius, 1792) are maritime while A. insularis Pittino, 2006 occurs on sandy river banks as well as on the coast. They are small beetles, 4.5mm, elongate with the elytra covering the abdomen, and in dorsal view the labrum is visible in front of the clypeus while the eyes are concealed.
APHODIINAE
Includes about 63 species in 11 genera. The large genus Aphodius Illiger, 1798 includes about 49 species but is very likely to be split into many other genera, mostly corresponding to what are now subgenera. Many are common and widespread and most are seasonal, occurring in the spring, summer or autumn and a very few are active through the winter. Oxyomus sylvestris (Scopoli, 1763) is a local throughout England and Wales, occurring among decaying vegetation and in carrion. Heptaulacus testudinarius (Fabricius, 1775) is very local across southeast England, it occurs among decaying vegetation and dung in the spring. Euheptaulacus sus (Herbst, 1783) is very rare in Southern England, occurring among vegetation on dry and sandy soils. E. villosus (Gyllenhal, 1806) is widespread but very local in decaying vegetation and dung. Saprosites Redtenbacher, 1858 includes 2 species; S. natalensis (Peringuey, 1901) was added to the list in 2003 while S. mendax (Blackburn, 1892), an introduction from Australia, is now established across the southeast. These species are distinctive; the eyes are visible from above but the labrum is concealed, the pronotum is smooth but for tubercles or depressions in some males and the elytral margin is straight. The meta-tibiae have 2 transverse ridges externally and the longer terminal spur is shorter than the first 2 tarsomeres combined. The remaining genera include small, 2.7-4.3mm, elongate species with the elytra entire and strongly sinuate before the middle and the pronotum with transverse ridges or depressions. The eyes are visible from above. Brindalus porcicollis (Illiger, 1803) is now extinct and Pleurophorus caesus (Creutzer, 1796), a western maritime species, is known only from old records. Rhyssemus germanus (Linnaeus, 1767) is known from old records from the Severn Estuary. Diastictus vulneratus (Sturm, 1805) is very rare; recorded from Sussex, under stones or among moss etc. around rabbit burrows. Psammodius asper (Fabricius, 1775) is a very local maritime species. Tesarius caelatus (LeConte, 1857), first recorded in 1976, is a very local maritime species. T. mcclayi (Cartwright, 1955) was added to the list in 1998 based on maritime records from South Wales.
SCARABAEINAE
Includes 2 genera which are very distinctive among the U.K. fauna, they are distinguished by the meta-tibiae bearing a single apical spur. Our single species of Copris Geoffroy, 1762, C. lunaris (Linnaeus, 1758) is a large, 14-20mm, shiny-black beetle with 9 longitudinal striae on each elytron. It is a very rare species of south-east England associated with cattle dung on sandy soils. Onthophagus Latreille, 1802 includes 8 species of small, 4-11mm, dung beetles which are uniformly black or dark with variously mottles elytra. Typically associated with dung but also occurring in decomposing fungi and carrion. Several are common and widespread. Members of this subfamily burrow beneath dung constructing vertical tunnels with lateral branches into which brood-pellets of dung are deposited.
MELOLONTHINAE
Includes the chafers Hoplia philanthus (Füessly, 1775), Serica brunnea (Linnaeus, 1758), Omaloplia ruricola (Fabricius, 1775) and 2 species each of Amphimallon Latreille, 1825 and Melolontha Fabricius, 1775 as well as the occasionally recorded Polyphylla fullo (Linnaeus, 1758) which has never been established. All are distinctive with the claws equal in length and each with a lateral tooth although Hoplia has only a single, longitudinally divided, claw.
RUTELINAE
Includes chafers with unequal meta-tarsal claws. Anisoplia agricola (Poda, 1761) is known only from old records. Phyllopertha horticola (Linnaeus, 1758) is common and widespread while Anomala dubia (Scopoli, 1763), the dune chafer, is a very local, mostly maritime species.
CETONIINAE
Includes very distinctive species which are immediately recognized by their general appearance. With the exception of the rose chafer, Cetonia aurata (Linnaeus, 1761), which is widespread and locally common across England and Wales, all are rare and very local. Of the ‘bee chafers’ Trichius fasciatus (Linnaeus, 1758) is widespread while T. gallicus Dejean, 1821 is only doubtfully British. Protaetia metallica (Herbst, 1782) is a northern English and Scottish species. Gnorimus nobilis (Linnaeus, 1758) and G. variabilis (Linnaeus, 1758) are southern English species. Oxythyrea funesta (Poda, 1761) has only recently become established in southern England. All species develop in decaying vegetation or dead wood and adults occur on flowers in hot weather.
Because the family is so very diverse the above discussion has been necessarily brief and superficial but detailed information can be found by following the subfamily links, and some of the variation in the details of the classification will be discussed. The British fauna can only provide the narrowest idea of the family and so a brief overview of this is given separately.
Subfamilies of the Scarabaeidae.
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AEGIALIINAE LAPORTE, 1840
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ALLIDIOSTOMATINAE ARROW, 1940
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APHODIINAE LEACH, 1815
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CETONIINAE LEACH, 1815
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DYNASTINAE MACLEAY, 1819
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DYMANOPODINAE ARROW, 1911
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EUCHIRINAE HOPE, 1840
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MELOLONTHINAE SAMOUELLE, 1819
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ORPHNINAE ERICHSON, 1847
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PACHYPODINAE ERICHSON, 1840
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PHILEURINAE BURMEISTER, 1847
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RUTELINAE MACLEAY, 1819
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SCARABEAINAE LATREILLE, 1802
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TERMITOTROGINAE WASMANN, 1918
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ACANTHOCERINAE LACORDAIRE, 1856