Nimbus Mulsant & Rey, 1870
This small genus of about 15 species was until recently included within a much more widely defined Aphodius Illiger, 1798, it is a Palaearctic group with ten species occurring in Europe. Of these European species only two, N. contaminatus (Herbst, 1783) and N. obliteratus (Panzer, 1823), are generally widespread and extend into the UK although N. affinis (Panzer, 1823) extends across the north-east and might be expected to find its way here. The other species are of restricted or very restricted distribution; N. marianii (Pittino, 1978) is restricted to France and N. richardi (Veiga, 1984) to Spain while N. franzinii (Pittino, 1978) is endemic to Corsica and Sardinia. N. proximus Adam, 1994 is a western species occurring in Portugal, Spain and France, while N. johnsoni (Baraud, 1976) occurs in Italy, Croatia and Greece, and N. lederi (Harold, 1876) is a mostly Russian species that extends into the Near East. N. orbignyi (Clouet, 1896) is a North African species that also occurs on the Canary Islands. All are small dung beetles. 3.0-7.0 mm. and typical of the subfamily, elongate and rounded at both ends, flattened above and below and pale brown with various darker markings. Head trapezoidal with angular genae and weakly emarginate clypeus, frontoclypeal suture weakly defined laterally and submentum with weakly defined fossa. Pronotum flattened, curved laterally from rounded posterior angles to distinct and sometimes slightly produced anterior angles. Lateral margins of the pronotum and elytra with long hairs, in most the surface is distinctly pubescent. Mesosternal process wide and flat; without a longitudinal keel and truncate across the apex. Elytra with complete impressed and punctured striae, often weakly dilated after the middle and continuously-curved apically, epipleura acutely angled along the entire length. Legs fossorial, middle and hind tibiae with small spines of varying length but without distinct ventral rows of setiferous punctures. Sexual dimorphism is not pronounced but males often have sparser pronotal punctures and in some the middle tibial spurs are short and truncate. Among the UK fauna they are distinguished by the pale colour, setose anterior clypeal margin, bordered pronotal base, short and impunctate scutellum and pubescent elytra. Our two species are readily distinguished by the extent of the dorsal pubescence.
Nimbus contaminatus 1
Nimbus obliteratus 1
Nimbus contaminatus 2
Nimbus contaminatus 3
N. contaminatus (Herbst, 1783)
This species occurs throughout Europe and North Africa, extending east into Asia Minor and western Russia and north into the UK and to some northern provinces of Fennoscandia; it is generally common throughout this range although very local and scarce in some northern countries e.g. Poland, Latvia and Belarus. Here it is generally common and often abundant across England and Wales, including Anglesey and Man, though less so in the north and much more local further north to Shetland and in Ireland. The typical habitat is open and rather dry grassland and dung pasture, often on dry or sandy soils but the presence of dung is the deciding factor; adults sometimes occur in deer or fox dung or at carrion or among decaying fungi or compost etc but only infrequently and in general are rarely found far from dung pasture. This is a mostly autumnal species; adults first appear in late August but usually emerge in large numbers following the first heavy rains in September or October and may they usually persist into December, they soon become common and across much of England and Wales they become the commonest species at this time, displacing some of the common summer species in cattle, sheep and horse dung. In higher northern latitudes they may also be common in moose dung. They are diurnal and on bright days may be seen swarming over dung pasture, they are strongly attracted to freshly deposited dung and fresh pats may soon contain large populations. Mating occurs after a period of feeding and females deposit eggs into the base of dung pats, adults generally die off during late autumn and early winter although specimens may occur in winter flood refuse or even at dung in the spring. Eggs overwinter and larvae emerge in the spring to develop through the summer and pupate in July or August. Adults may be sampled by all the usual methods associated with dung and they will usually be found in large numbers; specimens will often be seen in flight and may occur in numbers in interception traps and cattle troughs.
5.0-7.2 mm. Long-oval, discontinuous in outline and with notably long legs, readily identified in the field by the overall colour and conspicuous pubescence. Head and pronotum substantially black with a bronze or blue metallic reflection, clypeus and anterior and lateral pronotal margins yellow, scutellum black, elytra brown with variable dark markings, usually the sutural margin and towards the lateral margins and two transverse series of blotches which may be joined, legs pale with the femoral and tibial apices darker, antennal clubs dark. Clypeus expanded and angular in front of the eyes and sinuate anteriorly, the anterior margin setose, surface uneven and finely punctured. Pronotum transverse, broadest about the middle and narrowed to widely rounded posterior angles and rounded but distinct anterior angles, surface sparsely and finely punctured and pubescent; the pubescence long and erect around the lateral margins, basal margin finely bordered throughout. Elytra broadest behind the middle, with rounded shoulders and a continuous apical margin, striae impressed and punctured to the apex, interstices finely punctured, with conspicuous pubescence which is usually longer and conspicuous towards the margins. Front tibiae with three external spurs in the apical half, middle and hind tibiae with three transverse series of stiff setae externally and paired terminal spurs, the longest of which is a little shorter than the basal tarsal segment. Tarsi with 5 simple segments.
N. obliteratus Panzer, 1823
This western Palaearctic species is widespread across southern and central Europe from Spain to Greece and extends into Asia Minor and western Russia, to the north it reaches the UK, Denmark and Poland but is otherwise absent from the Baltic countries; through much of this range it is sporadic and very local and in the north generally scarce. In the UK it is locally common in southeast and central England and Wales, including Anglesey and there are a few scattered records further north to the Scottish Highlands and from Ireland. An oligotrophic species which occurs in a variety of habitats but usually on light or sandy soils, it is sometimes common on dung pasture but often occurs in woodland and scrub, and while it generally displays a preference for horse dung compared with cattle dung it has been recorded in every type of dung as well as, very occasionally, decaying vegetation and carrion. Adults are active from August until November or December, usually peaking in abundance during October, but specimens have been found through the winter and into the spring. Mating occurs in the autumn and it is likely that eggs are the main overwintering stage as it seems only small numbers of adults survive the winter, larvae develop through the spring and summer and new-generation adults eclose in July and August although generally remain in situ until September when they emerge and swarm.
4.5-7.0 mm. Very similar in colour and shape to contaminatus but lacking the fringe of long hairs to the lateral pronotal and elytral margins, and the elytra are glabrous across the base. In series a difference in elytral pattern becomes obvious; in the present species the darker markings are more diffuse and less well-defined, they are also more variable and in darker specimens may extend substantially across the base from the suture.