Beetles in dung
Many species of beetles representing a wide range of families occur in dung, the most numerous and usually most obvious are members of the Scarabaeoidea but hydrophilids, histerids and staphylinids will usually be common along with abundant diptera larvae and mites etc. Dung is energy rich and abundant and so many insects have evolved to utilise it as food for their developing larvae, these in turn have attracted many predatory and parasitic species, both of beetles and other insects e.g. earwigs and various bugs (Hemiptera, Saldidae and Lygaeidae) will often be encountered. Ants are often abundant in old and dry dung and parasitic wasps may occur about any type of dung, many species of a wide range of families of diptera will be abundant in dung and other invertebrates such as centipedes and springtails will usually be encountered. Most of these species will be of no interest to the coleopterist, but with experience the number and variety of insects present in a sample will often indicate the types of beetle likely to be found and whether it is worth investigating. The easiest way to start looking for dung beetles is to search through dung samples on cattle pasture or bridle paths, these are easy to find and investigate but beyond the obvious ‘dung beetles’ there are many species that will become familiar with extensive searching e.g. old and dry dung is often disappointing but will sometimes host not so obvious beetles such as monotomids, ptilids and cryptophagids such as Ootypus and various Atomaria. A wide range of species will occur from early spring but for various reasons searching should continue through the year; many species are seasonal and dung will typically host different species as it ages and dries out i.e. the fauna tends to be successional and so continued searching may reveal a wider diversity, beyond this most species associated with dung are highly mobile, they fly well and are quickly attracted to fresh samples from a wide area. Many beetles may thus be netted in flight over dung pasture, especially in hot weather, and a good method of sampling is to disturb a recent dung
Horse (top) and cow (bottom) dung.
sample and simply wait for the beetles to fly in, which they will, and usually quickly and in numbers, on the other hand many are active in the evening or at night, these may also be netted in flight and many will also come to light. This sort of thing will keep the beginner interested for a few seasons but beyond the obvious cattle and horse dung it will be very rewarding to search other types, canine, badger and fox droppings are less pleasant to investigate but often provide interesting silphids, leiodids and histerids as well as many of the usual suspects, dried out rabbit and deer pellets are often crammed with species that do not frequent dung pasture, especially when investigated in wooded areas, and stored straw and dung mixtures can provide enormous numbers of specimens. The diversity will increase when samples from different biotopes are investigated e.g. samples from acid moorland, chalk grassland and coastal dunes will likely include many common species but among these are likely to be more specialized ones. The way to accumulate specimens and records of the majority of UK beetles associated with dung is therefore to search different habitats and areas through the year, this will very quickly provide a long list of species and records but there are a few methods that will increase this greatly, these are basically various forms of trapping and extraction and these will be discussed below, but the collector should realize that there is far more to dung sampling than Scarabaeoidea, and we hope the following brief overview should serve to illustrate this so that the large diversity of beetles occurring alongside the classic dung beetles are not ignored. Several families will be briefly considered later on but we begin with the two most prolific groups i.e. staphylinids and Scarabaeoidea.
Many species representing most of the subfamilies of rove beetles may be found in dung, most are predatory or saprophagous but species of Aleochara Gravenhorst, 1802 are an exception as the larvae are parasites of diptera pupae. Some predatory species occur in low numbers but dung staphs in general tend to colonize new dung samples quickly and so occur in large numbers. The following is intended only to show that it really is worthwhile sampling dung for staphs and that good reference material can quickly be collected. The most common and widespread of our Micropeplinae, Micropeplus porcatus (Paykull, 1789), has been recorded from old cattle dung, this is probably unusual as all our species occur more generally among decaying vegetation where they feed on fungal mycelia, but it demonstrates the variety of species which may be found. Of the Proteininae, species of Proteinus Latreille, 1797 may be abundant in dry dung samples, and at least two species of Megarthrus, M. depressus (Paykull, 1789) and M. denticollis (Beck, 1817) are often abundant in drying cattle and horse dung. Among the Omaliinae three genera are variously associated with cattle and horse dung although only a few species of Omalium Gravenhorst, 1802 are at all common, others include Deliphrum tectum (Paykull, 1789) and Acrolocha sulcula (Stephens, 1834). Oxytelinae includes several species that are widespread and very abundant in dung, in fact some are probably among the commonest UK rove beetles, among these are Platystethus arenarius (Geoffroy in Fourcroy, 1785), Anotylus tetracarinatus (Block, 1799), A. sculpturatus (Gravenhorst, 1806), A. rugosus (Fabricius, 1775) and Oxytelus laqueatus (Marsham, 1802), these will soon be found when sampling dung but several other species such as Aploderus caelatus (Gravenhorst, 1802) are also likely to occur. Among the Tachyporinae various species of Tachinus Gravenhorst, 1802 e.g. T. laticollis Gravenhorst, 1802 and T. marginellus (Fabricius, 1781) regularly occur about dung, and several Tachyporus Gravenhorst, 1802 will sooner or later appear. Aleocharinae is a very difficult group to become familiar with because it is large and includes many very similar species that are difficult to key and often need to be dissected, but several distinctive genera e.g. Autalia Leach, 1819 and Aleochara Gravenhorst, 1802 can easily be identified as there are good keys, and species such as the widespread but local Nehemitropia lividipennis (Mannerheim, 1830) and Tinotus morion (Gravenhorst, 18012) will soon become familiar, At least 30 species, which are variously included within the genus Atheta Thomson, C.G., 1858, will regularly occur when working dung, this genus has been split and consolidated ad nauseam over the centuries
and has become something of a dumping ground best left alone until good genetic data are available to demonstrate relationships between the various groups of species, nonetheless keys are available and with practice and familiarity many specimens can be assigned, but it is a difficult and frustrating task. Identification of much of this group relies at present on translations (of varying quality) of various European works, and even this process requires a certain familiarity with the group and experience with dissecting, but this is likely to change in the future with the publication of the final (or second) volume of Beetles of Britain and Ireland by Andy Duff, the point being that it is probably best to collect these tiny staphs but wait until comprehensive keys are available. Frustrating, but something to look forward to. Some species of Tachinus and Aleochara are moderately large and can hardly be missed, furthermore some, e.g. A. lanuginosa Gravenhorst, 1802 or A. curtula (Goeze, 1777), may occur in large numbers which makes them all the more conspicuous, but most of the larger and easily found species are members of the Staphylininae. Some of these are common but very elusive because they move rapidly and are easily disturbed, Creophilus maxillosus (Linnaeus, 1758) and species of Ontholestes Ganglbauer, 1895 behave like this, they are active in bright sun and run rapidly about dung as they predate other insects, they are often only glimpsed before they fly off or run into the soil and so will need to be searched for very carefully, the very rare Emus hirtus (Linnaeus, 1758) also behaves like this. The majority of our larger staphs may be found within or under dung, they also move rapidly but if a sample is pulled apart over a tray they can be collected easily as they fall. Through most of the spring and summer there is likely to be large or very large numbers of staphs in samples on dung pasture and so it is probably best to take only a few until they become familiar. The most diverse genus in dung is Philonthus Stephens, 1829 and many of these are large and conspicuous, a few such as P. marginatus (Müller, O.F., 1764) are easily identified in the field but at first the majority will all look the same and so specimens will need to be taken and examined. About twenty species occur in dung and in general they may be recognized by their shiny black or partly metallic colour and, in many, the double series of pronotal pores, as ever some will need to be dissected. Generally larger and much more colourful, our three species of Platydracus Thomson, C.G., 1858 are all associated with dung, and our two species of Staphylinus Linnaeus, 1758 as well as various Tasgius Stephens, 1829 and Ocypus Leach. 1819 may occasionally occur about older samples. The other group generally well-represented in dung is the Xantholinini Erichson, 1839. Species of Xantholinus Dejean, 1821 are eurytopic and occur in dung as well as among any decaying organic matter, similarly Leptacinus batychrus (Gyllenhal, 1827) may occur, but several Gyrohypnus Leach, 1819 may be expected from most samples of cattle and horse dung. Identifying the larger staphs is relatively straightforward as there are two very useful Royal Entomological Society handbooks that cover all the species as well as the smaller members of the Oxytelinae.
All our species of Geotrupidae are associated with dung although the very local Odonteus armiger (Scopoli, 1772) also occurs among subterranean fungi. They are large and very conspicuous beetles that can hardly be missed, adults may be found among samples of dung or their presence may be inferred by the tunnels they excavate below dung, they often crawl in the open or fly on warm sunny days and all fly during the evening. Male Typhaeus typhoeus (Linnaeus, 1758), with their large thoracic horns, are the most spectacular of our dung beetles and are common enough to be found by general searching. Many species of Scarabaeidae are often referred to as true dung beetles as they spend most of their life within dung, leaving only to disperse and fins fresh host material or, as larvae, entering the soil to pupate, Of the Scarabaeinae, all our Onthophagus Latreille, 1802 are associated with dung although they will sometimes also be found among decaying fungi etc., while the spectacular Copris lunaris (Linnaeus, 1758) is probably long extinct in the UK. The other group invariably associated with dung is the Aphodiinae which includes many common and widespread species which are invariably present in herbivore dung although many may also be netted in flight, especially in spring and early summer, and many also occur among decaying organic matter generally. Most were formerly included in the single genus Aphodius Hellwig, 1798 but this has recently been extensively divided and now only three species remain, of which the strikingly bicoloured A. fimetarius (Linnaeus, 1758) is widespread and generally common. There are several species that are so common and distinctive that they will soon become familiar and easily recognized in the field, these include Otophorus haemorrhoidalis (Linnaeus, 1758), Teuchestes fossor (Linnaeus, 1758), Acrossus rufipes (Linnaeus, 1758), Volinus sticticus (Panzer, 1798), Nimbus contaminatus (Herbst, 1783), Colobopterus erraticus (Linnaeus, 1758) and Chilothorax conspurcatus (Linnaeus, 1758), while many others will need very careful examination e.g. the smaller black species including Agrilinus ater (De Geer, 1774) and Calamosternus granarius (Linnaeus, 1767). There are several pairs of very similar species such as Melinopterus sphacelatus (Panzer, 1798) and M. prodromus (Brahm, 1790), or Aphodius foetidus (Herbst, 1783) and A. pedellus (De Geer, 1774), and some species are variable in size and colour e.g. Acrossus depressus (Kugelann, 1792), and so it will take a good deal of time and field work to become experienced with the group as a whole. Some species have more specific requirements e.g. Liothorax niger (Illiger, 1798) and L. plagiatus (Linnaeus, 1767) occur among
decaying organic matter around the margins of ponds and streams, Oxyomus sylvestris (Scopoli, 1763) rarely occurs in dung but is sometimes common among dung mixed with straw in stables etc. Limarus zenkeri (Germar, 1813) is a local species that occurs sporadically in dung but we find it repeatedly in cattle troughs, especially near wooded areas, in a range of habitats. Heptaulacus testudinarius (Fabricius, 1775) occurs in dry dung on sandy soils and is restricted to a few sites in South Hampshire while Ammoecius brevis (Erichson, 1848) occurs in moist rabbit droppings on sand dunes at a few sites on the north east coast of England. About forty members of the Aphodiinae are associated with dung and from the examples above it should be realized that the group offers good opportunities to find local or rare species beyond their known ranges and so contribute to the knowledge, this is especially significant as many species are thought to have declined over recent decades.
Another family well-represented in dung samples is Hydrophilidae, and more especially members of the subfamily Sphaeridiinae Latreille, 1802. The most conspicuous of these are species of Sphaeridium Fabricius, 1775, of which four occur in the UK and three are common and widespread, they are medium sized, 4-7.5 mm. oval and distinctively coloured, they live in wet dung and both adults and larvae are predatory. Beyond these most are small beetles but it is a diverse group and so repays sampling and studying. Dactylosternum abdominale (Fabricius, 1792) occurs among decaying organic matter in a wide range of situations and is sometimes common in manure heaps, it was first recorded from the UK in 2003 and is now widespread across the south east. Twenty two species of Cercyon Leach, 1817 occur in the UK and many may be found in dung, often in large numbers, these are small and rather nondescript beetles but easy to collect and relatively easy to identify. Other tiny members of this subfamily common in dung include three species of Cryptopleurum Mulsant, 1844 and two species of Megasternum Mulsant, 1844.
Of the Histeridae members of at least five genera commonly occur in dung, most common and widespread is Hister unicolor Linnaeus, 1758 while the very rare H. bissexstriatus Fabricius, 1801 occurs throughout Southern England and parts of Wales and H. quadrimaculatus Linnaeus, 1758 is restricted to a few sites in South East England, two other members of the genus are now thought to be extinct in the UK. Other genera likely to be encountered include Margarinotus Marseul, 1853, Atholus Thomson, C.G., 1859 and Onthophilus Leach, 1817. Histerids are predatory both as adults and larvae and so most dung species may also occur in decaying fungi and among compost etc, but sampling dung is a good way to find numbers of a range of species. Onthophilus are unusual in that they can run fast and are often active in warm sunny weather, in much the same way as the rove beetles Ontholestes, and so may be seen about dung by careful observation.
Many species of Ptiliidae will be found when working organic matter from almost any situation and dung is no exception, the range of genera is rather limited but a good range of species from the following should be expected: Ptenidium Erichson, 1845, Ptiliola Haldemen, 1848, Ptiliolum Flach, 1888, Nephanes Thomson, C.G., 1859, Baeocrara Thomson, C.G., 1859 and Acrotrichis Motschulsky, 1848. Ptilids will occur in large numbers when working old and dry dung samples and so do not need to be searched for specifically, and pootering a good sample of beetles will invariably provide a range of species. Adult ptilids are very distinctive because of their small size and feathery hind wings but specific identification can be very difficult, often involving dissection, but the genera are often distinct enough to be recognized with a hand lens and so after a while it is easy enough to become selective about which genera to take.
Beyond this very brief survey of beetles likely to be encountered at dung there are many that will appear randomly, e.g. elaterids sometimes occur on or even within dung as many develop as larvae in the soil, and we have taken Chrysolina marginata (Linnaeus, 1758) on dung at night on local moorland, this species rests by day in dense turf and becomes active in the evening, other rather random species we have found on dung include cantharids and nitidulids. Many UK beetles occur more generally among decaying organic matter and some will occasionally occur at dung, either randomly or perhaps attracted by certain volatiles, thus we have found specimens of Corylophidae, Clambidae and Anthicidae on dung, and random carabids and staphs will regularly occur, in our experience Notiophilus biguttatus (Fabricius, 1779) and various Amara species are often present among turf close to dung.
Finding Dung Beetles
And so searching dung, and not just cattle and horse dung, will provide a long list of species from a single area that will quickly increase by sampling through the year and then by visiting sites further afield or in different biotopes. But actually obtaining specimens from a sample of dung can be difficult for some people. The simplest way to find dung beetles is to find a sample and search through it using your fingers. This may not come easily to some people but herbivore dung is unlikely to do you any harm, one soon learns to ignore the aromas and once the beetles start to appear such things are forgotten. There are certain methods e.g. using latex gloves or smearing something pleasant-smelling under the nose, employed by the faint-hearted but it is usually quite quickly realized that such things are a nuisance and soon abandoned. It helps to collect near to a river or other water source for obvious reasons. Searching a sample like this will reveal plenty of beetles and may also uncover tunnels in the soil beneath the sample which will often accommodate Geotrupes, Onthophagus or certain Aphodiinae. Tunnels can be investigated with a trowel but for the purpose of collecting are best left alone as digging them up tends to be destructive. Cattle and horse dung will soon repay investigation but it cannot be stressed enough that other types of dung should always be investigated, e.g. on a sun-baked hillside in the Chilterns without a dung sample for miles we once found huge numbers of Onthophagus joannae Goljan, 1953 as well as a few specimens of various aphodiines by breaking apart rabbit and deer pellets. Most dung pasture will include a few cattle troughs and these should always be examined carefully as beetles tend to get caught on the water and find it difficult to escape. Liquid dung is difficult to work with and the best thing here is to carefully work through it with a trowel, this is worthwhile as some species e.g. Sphaeridium, prefer this sort of dung. But the majority of beetles are likely to be missed when working samples in this way, many staphs will run so quickly and vanish into the soil or take flight that by the time they are seen it is too late to catch them, and many beetles within the sample will remain still and be so covered in dung as to be invisible, they really are easy to miss. All but the wettest samples can be sieved and this method will reveal most of the beetles present. A few steep-sided white trays will be needed because very often so many beetles fall from the sample that a single tray becomes so full of debris and specimens that it becomes difficult to work through. This method is especially good when looking for smaller species that tend to be almost impossible to find by searching through a sample manually, most specimens will remain still for a while and so patience will be needed but they soon become obvious when start to move in the tray. On the other hand many staphs will run quickly in the tray and soon take flight, especially on warm or sunny days, they will need to be tubed or pootered quickly but a good supply of tubes will be needed as they should be kept apart for obvious reasons. For a serious dung sampling session it is best to take a few hundred tubes. Sieving will quickly provide many more specimens than can be easily dealt with and so the use of a killing bottle is often necessary. The best kind of sieve should have a mesh of about 1 cm and deep sides, the sample should be worked vigorously and then left for a while and worked again to dislodge any specimens that did not fall the first time. This method is also valuable when working dung from the edges of ponds and streams as a good amount of associated leaf-litter and debris can be included.
Various trapping methods can be employed to sample dung beetles but their use should be carefully considered as they tend to trap very large numbers of beetles, as well as many other insects, as so they can be, and usually are, very destructive, especially when they are designed to kill the specimens as they are trapped. Flight-interception traps are useless unless the container is filled with water and a drop of detergent to help the specimens drown as they drop from the vanes, they can produce lots of specimens but these will include many other insects and so are unnecessarily destructive. On the other hand Malaise traps can be a wonderful way of finding out what insects are present, especially if placed over a few dung samples, they are not destructive but require a fair amount of effort and will need to be monitored carefully as they tend to attract humans as well as insects. Many dung beetles fly in the evening or at dusk and so light traps may be effective, some species such as the spectacular Typhaeus, the very rare Odonteus or the ubiquitous Acrossus rufipes (Linnaeus, 1758) are noted for appearing at light traps, and other species will appear but it is probably not a rewarding way of sampling dung beetles as they are more easily obtained in other ways, but attending light-trapping sessions run by lepidopterists is usually productive. Pitfall traps placed near to a dung sample can be very productive, especially when baited with dung, but they will need to be inspected and emptied regularly and again they are likely to catch many ground beetles and other things not necessarily associated with dung. The best traps involve placing a sample of dung into a nylon mesh bag and suspending it over a bucket of water, the beetles will fly to the sample and many will fall into the water, again this can produce huge numbers of beetles, the majority of which will die off, and so careful consideration should be given to their use. All these traps are often left out for days or weeks, protected with rain shields and loaded with detergent or other killing medium in an effort to record the majority of the dung beetle fauna in a given area but always bear in mind how destructive they can be. A variant on this is Winkler extraction, here a sample is placed in a small mesh sack and suspended over a collecting vessel, as the sample dries out the beetles burrow out and fall into the vessel, this process may take a few days and unless the vessel is sealed to the bag it is likely that many specimens will be lost, but it can be a very thorough way of extracting beetles from a sample. It should be noted that trapping dung beetles can provide quantitative data that can be compared with past or future trapping events, and such data can, at least in an ideal world, be used to ascertain whether individual species are increasing or in decline, or whether the entire biomass is changing, over time it may also be indicative of whether such things as climate change or the use of antibiotics in cattle is affecting dung beetle diversity or abundance. Fair enough, but unless there is a very good reason for trapping thousands of specimens such things should be avoided. The very best way of sampling dung beetles is also non-destructive and very easy to employ, although it can be extremely unsociable. From personal experience we know that this method can be unsociable to the point that its use soon becomes questionable but it is the very best way of sampling dung beetles, it’s also very enjoyable and fascinating, and it goes like this. Take a sample of dung from the field and seal it in a polygrip bag, a kilogram is usually plenty and several samples can be taken if they are going to be dealt with quickly, once home have plenty of tubes ready, empty it into a bowl of water and break it up and wait for the beetles to float to the surface, which they will and usually in numbers, the majority of dung beetles will float happily until rescued but most of the staphs will instantly take flight and head to the nearest window. This will need to be done inside so that the specimens do not escape, a shed might be ideal, and a Malaise trap would be perfect, but excellent results are obtained in the average kitchen. Apart from providing endless specimens his method will quickly hone ones skills as there are very few experiences to match trying to pooter interesting-looking oxyteline staphs from among several thousand specimens silhouetted against a window from a net curtain.
It must be said that as interesting and diverse as the dung beetle fauna is, by employing various sampling methods the local fauna will soon become familiar and collecting trips will soon start to produce the same old species list. Sampling should continue through the year and as many local sites as possible should be sampled but eventually you will need to travel to obtain new material, this should always be productive because the methods employed to good effect locally can used elsewhere and good samples can quickly be taken, the common species will always constitute the majority of a sample wherever it is taken and so it is vital to know what is different or worth taking, fortunately all this sort of thing can be learned locally and at leisure before venturing further afield. The UK dung beetler is also very fortunate in that very good keys are available to all the groups of beetles likely to occur in dung with the exception of some groups of staphs, there is also a wealth of information on line about all aspects of working with dung beetles and certain social media groups will usually provide reliable identifications to help the novice on their way.