CETONIINAE Leach, 1815
Only poorly represented in Britain, most of our species are very local and rare. At present only the rose chafer, Cetonia aurata is frequently encountered.
This large and very diverse subfamily includes many spectacularly-coloured and metallic species and is popular with collectors worldwide, there is a substantial trade in tropical specimens and many from around the world can be found for sale online, some species are reared or kept as pets and there are many vast public and private collections around the world. Shiny metallic chafers are used in jewellery and ornaments and vast numbers of beetles are either reared or collected from the wild, quite legally, to meet this need and in some tropical area, particularly in south-east Asia, they are an important source of income for many families. Beyond the bulk supply of specimens for trade purposes there is also a worldwide trade in rare and unusual specimens and some, particularly the massive and spectacular Goliath Beetles, which are beautifully-patterned and may reach 110mm in length, and fetch appropriately spectacular prices. The subfamily includes about 4000 described species and there are many more to be described, diversity is greatest in Old World tropical and subtropical regions and falls sharply with increasing latitude, the New World fauna includes about 300 species, of which more than 100 occur in North America, and Brazil, with more than 70 species, is probably the most diverse Neotropical country. With the general exception of oceanic islands, including New Zealand but definitely not Madagascar, and higher latitudes in both hemispheres, the subfamily is represented worldwide. Classification, particularly at the generic level, and particularly with tropical faunas, is difficult because historically many species have been assigned to genera without well-defined limits and collecting has been rather territorial, hence for reasons best assigned to empire, various collections in developed countries have concentrated on certain accessible parts of the world and over the centuries various ideas of classification have been constructed, this has hardly been helped by a massive profusion of names concocted by collectors etc. for aberrations, colour varieties and subspecies, but a modern system recognizes 12 tribes, 6 of which occur in the New World, and a variable number of genera. Having said that, the limits of the tribes and placement of many genera remain uncertain, and sometimes the group is given family status and some of the tribes e.g. Cetoniini Leach, 1815 and Trichiini Fleming, 1821, will sometimes be found in the literature as subfamilies. Most of the tribes and subtribes are largely restricted to particular regions and the subfamily displays a very high level of endemicity; more than 90% of genera are restricted to a particular biogeographical region, this is highest in Madagascar, where about 95% of genera are endemic and lowest in the Palaearctic region where about 40%
of genera are endemic. The greatest generic diversity is in the Afrotropical region and this is also a region of very high endemicity. The much admired and desired Goliathini Griffith & Pidgeon, 1832 includes about 80 genera in 4 subtribes and is restricted to warmer areas worldwide, only 4 species of 2 genera occur in the New World (Mexico) and diversity is greatest in Africa and south east Asia. Gymnetini is the only primarily Neotropical tribe; of the 29 known genera 25 occur in South America. Cremastocheilini Burmeister & Schaum, 1841 includes about 50 genera and occurs in warmer regions worldwide with the exception of Australia, 10 genera occur in the New World and diversity is greatest in the Old World tropics, especially Africa, with about 60 % of genera although none occur in Madagascar, and south-east Asia. Trichiini Fleming, 1821 includes about 43 genera in 5 subtribes, one is restricted to the Neotropical region and two are African while Osmodermina and Trichiina occur worldwide except for Australia. The primarily tropical tribe Valgini Mulsant, 1842 includes 33 genera and is almost cosmopolitan although only 2 genera occur in the New World and only a single species is known from Europe. Xiphoscelidini Burmeister, 1842 includes 14 genera, it is primarily African with a few species occurring in Madagascar and Australia. Stenotarsiini Kraatz, 1880 includes 48 genera in 10 subtribes, it is very diverse in Madagascar but is also represented in Mauritius and the Comoro Islands. Taenioderini Miksic, 1976 includes about 25 genera in 2 subtribes and is more-or-less restricted to the Oriental region from India to central and southern China and extending south into Indonesia and Philippines, and a very few species occur in Papua New Guinea and the Solomon Islands. Schizorhinini Bermeister, 1842 includes 36 genera in 2 tribes; it is mostly endemic to the Australasian region with only a few species occurring further north into India and south East Asia, and the majority of the Australian fauna are included in this tribe. Phaedimini Schoch, 1894 is a small and mostly Oriental tribe of only 4 or 5 genera. Diplognathini Burmeister, 1842 includes 22 genera and is primarily Afrotropical, with a few species occurring in the Oriental region. Cetoniini Leach, 1815 is the largest tribe with about 107 genera worldwide; it is very widespread but primarily an Old World group with only 4 genera occurring in the New World. It is very diverse throughout the Old World tropics except for Australasia and Madagascar but is only relatively poorly represented in northern temperate regions; 7 genera and 39 species occur in Europe (although the eastern Palaearctic, which also hosts many primarily Oriental genera, is much more diverse than western areas), and of these only the very widespread Cetonia aurata (Linnaeus, 1758), Protaetia cuprea (Fabricius, 1775) and Oxythyrea funesta (Poda von Neuhau, 1761) extend north to the UK. Cetonia Fabricius, 1775 otherwise includes about 25 species and numerous subspecies and is mainly Palaearctic and Oriental in distribution, 4 species occur in Europe but only C. aurata is widespread. Protaetia Burmeister, 1842 is a large genus of up to 250 species (depending upon how it is defined) and occurs throughout the Old World with the exception of most of Africa, it is the largest of the European genera with 24 species. The genus is naturally absent from the New World but P. fusca Herbst, 1790, the Asian Mango Flower Beetle, has spread to warmer areas across the world and has been established in the United States since 1985. Oxythyrea Mulsant, 1842 includes up to 110 species and occurs throughout the Palaearctic and African regions, including Madagascar.
The European fauna is small compared with adjacent areas of Africa and Asia; it includes 48 species of 11 genera and 3 tribes, and of these only 7 species of 5 genera and 2 tribes extend to the UK. Valgini is represented by a single widespread Eurasian species, Valgus hemipterus (Linnaeus, 1758) which is present on many Mediterranean islands and extends north to the southern Baltic countries, and since the 1980’s has become established in North America, but does not (yet) occur in the UK. Trichiini is represented in Europe by 2 (from a total of 5) subtribes; Osmodermatina Schenkling, 1922 includes 2 species of Osmoderma Lepeletier & Serville, 1828, and Trichiina includes 3 species of Gnorimus Lepeletier & Serville, 1828 and 4 species of Trichius Fabricius, 1775. Cetoniini is represented by 2 (of about 10) subtribes; Cetoniina Leach, 1815 includes 5 genera, Aethiessa Burmeister, 1842 (1 sp.), Cetonia (4 spp.), Heterocnemis Albars, 1852 (1 sp.), Protaetia (24 spp.) and Tropinota Mulsant, 1842 (2 spp.) and Leucocelina Kraatz, 1882 includes 2 genera, Oxythyrea (6 spp.) and Paleira Reiche, 1871 (1 sp.).
Valgus hemipterus is one of the most common chafers in Europe, and highly likely to be found in the UK soon.
This subfamily includes some of the largest and most massive of all beetles; males of some species of Goliathus exceed 100mm and are otherwise very broad and heavily sclerotized, and many tropical species exceed 50mm but the majority are smaller, between 15 and 30mm in length; the smallest and largest European species are Valgus hemipterus (5-10mm) and Osmoderma eremita (Scopoli, 1763) (24-30mm). Colour and pattern vary enormously although in northern temperate regions most are black or various shades of green, metallic or otherwise, and most lack distinct patterns-species of Trichius or the American Euphoria fascifera LeConte, 1861 being notable exceptions-and many species in warmer regions are also black or otherwise drab, but the group is generally desirable, at least in large part, among collectors and commercially-interested parties due to the strikingly patterned and brilliantly colourful and metallic appearance of tropical species. Variation in colour and pattern is a feature of many species and has given rise to a mountain of often confusing sub-specific names, similar things happened among other popular groups such as longhorns and larger ground beetles but the heyday for this sort of thing seems to have passed and most names-other than valid sub-specific names-have become redundant and are largely ignored, but it is easy to understand why such named were used as a well-laid out and labelled drawer of metallic chafers is a truly satisfying thing. Yellow, green and coppery or violet are common in tropical species, blue much less so, and many are polychromic in the sense that they may appear yellow, green or blue depending on the angle from which they are viewed, most patterns consist of contrasting maculae , streaks or margins and the straightforward bicoloured forebody/elytra arrangement seen in many families is unusual, the size and extent of maculae and spots can vary widely in a single population of a single species and in some e.g. species of Marmarina Kirby, 1827, the entire body is covered in tiny contrasting spots of colour. A good idea of colour and pattern variation can be seen in the genus Pachnoda Burmeister, 1842, these are commonly known as sun-beetles and one species, P. marginata (Drury, 1773) along with about 10 subspecies, is widely available for rearing as larvae, pupae or adults in many fascinating colours. Old World Goliath beetles, prized among collectors and the like, are very varied but most are easily recognized by their distinctive pattern of pale lines on a dark red or brown background, and some Neotropical members of the genus Gymnetis MacLeay, 1819 must surely qualify among the most beautifully coloured and patterned of all beetles. Most species are largely glabrous, and pubescence is more common on the underside or the legs but some tropical groups e.g. species of the South African genus Trichostetha Burmeister, 1842, most of which live at high altitudes, have long but sparse pubescence while members of the Australian genus Trichaulax Kraatz, 1880 have lines of dense pubescence on the elytra and Afrotropical species of the large genus Microvalgus Kraatz, 1883 have distinct scales both dorsally and ventrally. Shape also varies hugely but typically they are broadly-oval and rather flattened dorsally, the head is narrow and the pronotum transverse, widest about the base and narrowed to a rounded anterior margin, the elytra are broad and parallel-sided with distinct shoulders and leave the abdominal apex exposed. More technically the group may be diagnosed as follows. Head small, usually with large convex eyes and lacking temples (from above), the vertex is simply convex, the frons and clypeus simple or variously impressed and the labrum weakly sclerotized or membranous and usually not visible. In most the mandibles are small, relatively diminutive and usually hidden under the clypeus or other mouthparts, and the eye-canthus is long and narrow. Antennae 10-segmented, short and distinctly clubbed; the scape is broadened and variously modified e.g. in the Cremastocheilini it is dilated into a broad triangular plate, the pedicel is smaller and the flagellum 5-segmented, the club consists of 3 elliptical and closely approximated segments which in tropical species may be very elongate. Pronotum very variable but usually transverse to quadrate and with distinct lateral borders; typically somewhat semi-circular with a sinuate basal margin but in many exotic forms the overall shape is transverse-pentagonal or hexagonal, often with the basal half parallel-sided or nearly so, in most the basal margin is sinuate and closely approximated to a large or very large scutellum but in Gymnetini it is produced back medially into a long lobe and the scutellum is not visible. The pronotal surface is usually smoothly convex but in some groups e.g. among the Valgini there are patterns of impressions or callosities. The prosternum is very variable but is typically smooth with closed and transverse, closely approximated coxal cavities placed in or towards the anterior half, in some groups there is a well-developed process between the coxae and the anterior margin is variously projecting. The mesosternum is short with transverse coxal cavities separated by an anterior projection of the metasternum and well-developed mesepimera, the metasternum is long and variously produced, sometimes very strongly so, into a broad lobe which projects forward between or above the middle coxae (this is very strongly developed in some groups e.g. Goliathini), the metepimera are long and narrow and the posterior margin rarely projects far between the hind coxae. In most the hind coxae are quite closely approximated (almost contiguous in Trichiini) and widely transverse, reaching the lateral margin, but in e.g. Valgini they are widely separated with the meso- and metasternal junction lying between. Abdomen usually with 7 distinct sternites and the pygidium exposed and immovably fused to the propygidium. Scutellum long and triangular in Cetoniini, variously shaped in other tribes. Elytra usually broad, rather parallel-sided and flattened dorsally, in most the shoulders are well-developed and the apical margin in continuously rounded, they mostly lack distinct striae, although in many there is a variously developed sutural stria and many have longitudinal impressions or ridges and in some groups the areas between these are variously pubescent. A well-developed post humeral emargination which allows the flight with the elytra closed is present in Cetoniini and Gymnetini but absent or less strongly developed in other tribes, this is coupled with an ascending and convex mesepimeron which is usually visible behind the posterior pronotal angles from above, again this is usually absent or wanting in other tribes. The legs are usually long and always very robust; the front coxae are convex to some extent and often strongly conical, the trochanters are long and obliquely connected to the femora which are usually broadly rounded and smooth although in some tropical groups they have apical projections which fit into basal internal angles on the tibiae when the legs are retracted. In many species the hind femora are larger or more developed than the others, an extreme example of this being seen in the Neotropical genus Blaesia Burmeister, 1842 (Gymnetini). The tibiae are long and well-sclerotized, the front tibiae often the longest, as seen in some Mexican Neoscelis Schoch, 1897, and usually with various external teeth or at least tubercles or spines towards the apex, the middle and hind tibiae also have external teeth or ridges but usually only one or two sets and there is often a longitudinal series of punctures along the inner margin, the inner apical angle has two long spurs and the outer angle may be produced into a ridge or armed with spines. The tarsi are usually 5-segmented although in the Afrotropical subtribe Trichoplina Krikken, 1985 (Cremastocheilini) they are 3-segmented, with all segments simple and robust, and all have paired claws which are nearly always more-or-less equal in length. This description is very general and the group varies hugely in detail but with a little experience the majority of species are readily recognized, among our UK chafers they may be distinguished by exposed pygidium, paired and equal claws which lack lateral teeth or lobes, and paired hind tibial spurs.
Sexual dimorphism is a general feature in many exotic groups, usually the head, pronotum and/or appendages are modified, usually in the male, and this can take extreme forms in tropical species where the fronto-clypeal area may be produced into a very large simple or bifurcate horn and the lateral margins of the clypeus produced into horns or plates, these modifications are common and are a general feature of some groups e.g. Goliathini, where the African Mecynorrhina polyphemus (Fabricius, 1781) is a good, if extreme, example, and some Chinese species of Dicronocephalus Hope, 1831 (Dichronocaphalina Krikken, 1984, Goliathini), males of which are known as elk-horn scarabs. The pronotum may be dimorphic in shape or proportions but structurally is rarely very different between the sexes, the Neotropical Pantodinus klugi Burmeister, 1847 (Incaina Burmeister, 1842, Trichiini), the so called ‘wrestling rhinoceros beetle’, being an exception with males having very large lateral projections.
Sexual dimorphism in Eudicella gralli
Cetonia aurata larva
Larvae are of typically scarabaeiform; C-shaped, large and fleshy, usually pale creamy coloured with the head and legs well-sclerotized and the spiracles usually visible as a dark spot on the lateral side of the thoracic and abdominal segments, they generally live among decaying organic matter and when fully grown are larger than the adults, most develop over 2 or 3 years and pupate in the autumn or spring in a oval cell composed of soil particles or fine fragments of host material. Most are glabrous or finely pubescent below and some may have darker patches to the dorsal surface of some thoracic or abdominal segments; cetonids larvae may be distinguished from those of other UK Scarabaeoidea by the following combination of features. Body uniformly curved; without the anterior part of the abdomen swollen as seen in Scarabaeinae, middle coxae without a stridulatory file, as in Lucanidae, tarsal claws short, antennae with 4 or 5 segments and lacking a sensillum at the apex of the penultimate segment, anus transverse and not angulate and the raster-a series of short and robust spines on the ventral surface of the last abdominal segment-consisting of 2 longitudinal rows of spines and sometimes also a patch of very short spinules, in the closely similar larvae of Rutelinae the raster consists of longitudinal rows of large spines surrounded by large patches of spines.
The greatest diversity of species occurs in tropical forests and despite the fact that adults of many species are good fliers and may occur in huge numbers, many have sedentary and protracted larval stages and a limited distribution and so are vulnerable to environmental abuse, thus it is likely that many species are under pressure from commercial deforestation and are likely to either decline or vanish altogether, the likelihood of this happening can only be imagined by researching the true extent of tropical forest abuse which, notwithstanding any impression given in the press, has increased alarmingly over recent decades and continues to do so. Adults of most species are diurnal, they feed on the nectar and pollen of a range of flowers, and most swarm in large numbers as they do so; this can still be seen in the UK when Cetonia aurata (Linnaeus, 1758) swarm on the warmest early summer days around flowering elder shrubs etc. Many also feed on fruit both as adults and larvae and this can be appreciated by rearing the readily available Pachnoda on mango etc, in tropical regions any fallen or damaged fruit might quickly become covered in a mass of feeding chafers, they are also attracted to sap and may be attracted to traps in large numbers with various fermenting fruits and sugar solutions. Larvae mostly develop over several years (at least in northern temperate regions) among decaying vegetable matter, they are saprophagous or saproxylophagous and commonly occur in soil, tree cavities or among decaying wood, some exotic species develop in dung and one African genus is known to be a parasite in Heliocopris subterranean brood chambers, depositing their eggs in their host’s dung balls. Some species of Cremastocheilini are associated with social hymenoptera, and in some the larvae are known to develop within nests and prey upon their host’s larvae. Unlike most other chafer groups only a very few cetonids are of any economic importance, the adults may damage flowers or leaves etc. and the larvae may stunt the growth of crops by damaging roots and stems but they are generally classified as minor pests. Our UK species are very typical of the group as a whole e.g. larvae of C. aurata develop among decaying vegetation in the soil or among soft decaying wood while Gnorimus nobilis (Linnaeus, 1758), G. variabilis (Linnaeus, 1758), Trichius fasciatus (Linnaeus, 1758), T. gallicus Dejean, 1821 and Oxythyrea funesta (Poda von Neuhaus, 1761) are associated with decaying deciduous trees. Larvae of Protaetia cuprea (Fabricius, 1775) are usually associated with nests of wood ants, Formica spp.) while adults feed on fruit and at sap.