Ontholestes Ganglbauer, 1895
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POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
STAPHYLININI Latreille, 1802
O. murinus (Linnaeus, 1758)
O. tessellatus (Geoffroy in Fourcroy, 1785)
Ontholestes murinus (Linnaeus, 1758)
This species is generally common throughout most of the Palaearctic region, extending east into China and eastern Siberia, it occurs throughout Europe from the Mediterranean to far above the Arctic Circle in Fennoscandia and has recently been recorded from Iran, it was first recorded in Canada (Newfoundland) in 1981 as an adventive species and since that time has become established and spread into the United States. In the UK it is common throughout Wales and England north to Nottingham and more local and rare further north to the Scottish border including Anglesey and Man and there are a few isolated records from the northern Scottish Highlands. Adults occur year-round and are active over a long season from early spring, they are associated with decaying organic material in any fairly dry situation; they are often common on dung pasture and will come to carrion, decaying fungi and compost etc. Both adults and larvae are predatory and are thought to prey mostly on Diptera larvae among host material. They are notably active in warm weather and can be very difficult to find, they arrive at host material by flight and will often sit on dung etc. for a while before exploring it but they will take flight or run into the soil or surrounding grass rapidly, and because of their cryptic appearance, especially in bright sun, they are very difficult to follow. They will occasionally be swept from vegetation in any habitat e.g. woodland or open grassland, and they can be sampled with dung or carrion baited traps and these methods often reveal the species to be common while other methods fail to find it. Little is known of the life cycle but mating pairs have been found in the spring and mature larvae and pupae have been sieved from garden compost in August, it is likely that larvae develop quickly as is normal for predatory insects among ephemeral host material and that adults overwinter in the soil etc. Fully grown larvae construct cell in the soil or among host material and pupate inside, under artificial conditions adults have eclosed within two to three weeks of pupation. Adults remain active into the autumn and so it is probable that winter is passed exclusively in this stage. Another notable feature of this species is its affinity for the most disgusting host material; we once unearthed a putrid black subterranean fungus from a chalk hillside in the Chilterns in south Buckinghamshire, it was in an advanced state of decay and the smell was unbelievably bad but the beetles soon arrived by flight and buried themselves into it, also arriving were large numbers of Onthophagus joannae Goljan, 1953 which swarmed over the fungus but were ignored by Ontholestes. We have also found them on canine droppings and under a decaying fish among reed-litter at Watford, Hertfordshire.
8-14mm. Distinctive among our fauna due to the brown and silvery pubescence, sharp anterior pronotal angles and dark legs. Body entirely black, dorsal surface with grey, brown and silvery pubescence which often forms a tessellated pattern and which has a metallic quality in life, legs black, the tibiae usually with brownish pubescence, antennae pale orange but variously darkened apically, Head transverse with large weakly convex eyes and short, slightly protruding temples, basal margin truncate, surface densely punctured and granulate, mandibles with a strong bicuspid internal tooth, antennae slender, the segments elongate at the base becoming quadrate towards the apex. Pronotum quadrate, parallel-sided to sharp and slightly protruding anterior angles and a curved basal margin, surface densely punctured and rugose. Scutellum large and triangular, usually with heart-shaped patch of dark pubescence. Elytra transverse with sloping shoulders and separately curved apical margins, surface uneven and densely punctured, the pubescence usually forming a symmetrical pattern of darker patches on a grey or brown background. Abdomen with strongly raised margins, curved laterally and densely punctured throughout, the basal tergites with discrete patches of dark pubescence either side of the middle, the fourth and sixth more evenly pubescent and the fifth extensively pale across the base and darker apically-in fresh specimens. Legs entirely black or with the tarsi variously pale red, front tibial margins entire to the apex, middle tibiae curved inwards towards the apex, hind tibiae straight, all with strong apical spurs. Basal segments of front tarsi strongly dilated in both sexes. Sexes very similar but males may be distinguished by the broader and more robust head; this is easily appreciated when specimens are compared.
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Ontholestes tessellatus (Geoffroy, 1785)
This species is also widespread across the Palaearctic region, occurring throughout Europe to the far north and east into China and eastern Siberia, it is locally common across southern and central England and Wales although generally absent from the West Country, and sporadic and scarce to the far north of Scotland and in Northern Ireland. Adults are present year-round and are active over a long season from early spring, they probably overwinter in the soil etc. but we have found them active in the winter among large decaying bracket fungi in a local wood, they are predatory and occur in decaying organic matter rich in fly larvae etc. but are less frequent at dung than the preceding species. Adults generally occur among compost or carrion and may be common among straw and dung mixtures stored as fertilizer through the warmer months, they fly quickly and powerfully and are quick to arrive at new host material, they may be found in any fairly dry habitat from woodland to grassland and occur among suitable material on coastal dunes etc. The life cycle is not well understood but adult numbers peak during May and again during August and September, suggesting a cycle similar to that of O. murinus: univoltine, breeding in the spring with larvae developing through the summer and the resulting adults overwintering. They are fast moving and hide or take flight very quickly when disturbed and so can be difficult to sample but they sometimes occur when sweeping and they regularly occur in dung and carrion baited traps, they should be looked for through the winter by taking samples of decaying fungi etc.
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15-22mm. Distinguished from O. murinus by the shape of the pronotum and the pale legs, from our other staphs by the dorsal pubescence and sharp anterior pronotal angles. Body black with dense variegated brown and grey pubescence which vary in extent but form a symmetrical pattern, the scutellum and basal abdominal tergites usually with sharply-defined dark patches, legs and antennal bases substantially red. Head transverse, with large eyes (though these are proportionally smaller than those of murinus) and rounded temples, surface densely punctured and rugose and mandibles with a large bicuspid internal tooth. Antennomeres 1-5 elongate, 6-10 progressively transverse, terminal segment emarginate across the apex. Pronotum rounded across the base, the posterior angles hardly developed, and broadened to acute and slightly projecting anterior angles, the lateral margin sinuate behind the middle and the surface densely punctured and rugose, usually slightly more strongly so than the head. Scutellum large and triangular, with dense dark pubescence which is often divided by a pale median strip. Elytra quadrate to slightly transverse, with sloping shoulders and distinct posterior angles, lateral margins curved and widest about the middle, surface densely and rugosely punctured. Basal abdominal tergites with well-defined patches of black pubescence, all tergites finely and densely punctured. Legs substantially pale, usually only the femora darkened around the middle. Front and hind tibiae more or less straight, middle tibiae expanded and curved inwards towards the apex. Basal segments of front tarsi strongly dilated in both sexes. Males may be distinguished by their broader head and much larger mandibles.