Nocturnal Beetles on Trees

Most of the species to be found by searching trees at night will be saproxylic, i.e. those that are closely associated with living or decaying wood. Many others will be found but it is the saproxylic species we are concerned with here because most saproxylic species are crepuscular or nocturnal. There are exceptions, most notably among the cerambycids, pyrochroids and scraptiids, but more generally beetles associated with wood are nocturnal. There are other ways of finding saproxylic species that are probably more productive in terms of diversity e.g. berlese extractions or flight-interception or sticky traps, and spreading out samples of wood pulp and debris from decaying trunks on sheets under hot sun will soon get the beetles moving, but searching at night with a torch has many advantages. Trees in any situation and in any stage of growth or decay are likely to be productive and even individual trees in domestic gardens may soon produce a decent list of beetles if sampled throughout the year, but established woodland and wooded parkland are the best sites, especially where they have a diverse mixture of tree species in various stages of decay. Some trees will be found to be more productive than others, not only in terms of species but also with individual trees, for some reason an individual oak tree among a series of similar oak trees will always be more productive even when there are no obvious differences between them, this is odd but it happens frequently and so as many trees as possible should be examined. For this reason it is good to choose a local site to survey, by doing so all the trees will soon become familiar and the best ones can be examined quite quickly. To produce useful data the usual notes should be taken i.e. date and locality, but other stuff is also valuable, most obviously the species of tree on which the specimen occurred and its condition, but if the temperature is noted a few times it will soon become obvious which nights are the best for sampling. As moth trappers will know, the phase of the moon can drastically affect the number of specimens arriving at a trap, and the same applies to beetles on trees; dark nights are always better than bright ones. Learning to identify a few trees is simple once it is realized that a dozen or so will always be found and

Damaged trees host lots of beetles, many of which are active nocturnally.

will constitute most of what is of interest; the most important will be Oak, Beech, Lime, Sycamore, Birch, Hazel, Hornbeam, Ash, Horse Chestnut, Alder, Willow, Rowan and Cherry, these are easily identified and learned although in fine detail things can get complicated e.g. Oak is a broad term that includes Turkey Oak, Sessile Oak, English Oak and others, but such detail will soon become obvious. Conifers are more difficult to identify because there are so many cultivars but the usual suspects include Pine, Spruce, Cedar, Redwood and Fir, these can also be learned quickly but they can be difficult in the field; Pine and Cedar are easy and Larch is deciduous and so easily identified in the winter. Using a local site will allow a daytime survey of the trees and so they should all soon become familiar. Fallen timber can be identified by association but old logs and decaying stumps that have lost their bark will often remain a mystery. After a few visits a routine will be adopted and a route around the site will develop which allows all the best trees to be visited several times although there are usually a few trees that are regularly so interesting that they consume most of the visits. Using a local site will also provide valuable experience so that when more remote sites are visited the sampling routines are already understood.

Equipment

Nocturnal searching demands very little equipment, at first all sorts of stuff will be taken but very little equipment is actually useful; a decent knife or two and a pooter are essential for extracting specimens from deeply fissured bark or cracked wood, a net is useful but better are those designed for working trunks, these are semi-circular and flexible so that they can be pushed around a trunk and the beetles brushed into them, they are also small and therefore easily carried, lots of tubes are useful because small beetles can be difficult to identify by torchlight and will need to be examined under the microscope, a small lens is obviously useful here, and finally, of course, a torch is essential. Head band torches are popular, they leave the hands free and they work very well but some people cannot get on with them as they can be uncomfortable. Torches need not be cumbersome as modern LED penlight designs can be very powerful and durable; a slim design that takes two or three AAA batteries is more than adequate for most work and spare batteries are easy to carry, they can also – as we know from vast experience – be held between the teeth while awkward specimens are dealt with. As a general guide it is worth investing in a good durable and weather proof torch of metal construction with an adjustable beam, an output of 120 lumens is quite sufficient and ideal for close work, a single LED model that takes two AAA batteries will work well for many hours with decent batteries, they are light weight and easily carried and slip into the pocket with no effort. Such a model can be found for about twenty pounds. At the other end of the scale, and these are absolutely great, are rechargeable models, these have higher light outputs, often around 300 lumens with a long beam distance although many have variable outputs as well, they have very powerful batteries that will last many hours and can be recharged many times, the downside is the price but a good compact model should be no more than fifty pounds, many models have various gimmicks such as heads that can be angled and twisted or magnets that will hold them steady, and while these may seem gratuitous they may also be worth considering. This last point should be explained, there will be many instances where things get very awkward e.g. when an interesting specimen is lodged among deep bark crevices etc, or when a branch or log needs to be held steady while a specimen is dealt with, and in such instances it soon becomes obvious that two people are much better than one and that if one person holds a couple of torches while the other deals with an awkward specimen then things are much easier. Whenever possible go out with a colleague or two. This also allows many more trees to be examined, it can also be useful for people like me that get disoriented easily in the dark and wander off in the wrong direction (I’ve spent a few enjoyable long nights lost in woodland on my own.) Some people prefer larger torches or lantern type designs but these usually give no more light output and are just cumbersome and heavy, there is no ideal choice and ultimately it is a question of personal preference, if in doubt try a few all night sessions and see how tiring it can be carrying lots of equipment.

Fermenting sap leaking from oak.

Sampling

Some trees e.g. Beech or Birch are easy to examine as they have smooth bark, while others e.g. Oak can be very difficult as they have deep bark that casts dark shadows and so they need to be examined much more thoroughly, but all should be examined as the most awkward are often the most rewarding. The best places to look are on bare wood that has dried and cracked but is surrounded by healthy bark, at night there should be no need to strip bark as the beetles will be active; sometimes it is best to spend ten minutes at a single tree; some species are photophobic and will retreat into crevices and so trees should be approached with the light directed at the ground, away from the wood until it is time to look for the beetles, other species seem to ignore the light altogether. There are a few things to look out for and these will become obvious with experience. The wood surrounding hollows containing avian nests should always be a focus of attention, as should cracked timber among loose bark that is extensively spider webbed, and the presence of tree ants can be a good indication of beetles. Two things that will produce an abundance of specimens are fungi and sap. Fungi should be treated with respect as they will host beetles throughout their existence, even when extensively decayed; spend some time looking without disturbing things and beetles should soon appear although where there are abundant examples it is obviously sensible to pull some material apart over a sheet or take some for extraction. Fungi will provide many species throughout the year and can be studied quantitatively through the season. Sap is easily found because the stains it produces on the bark will persist over a long period, but the right sort of sap is rather infrequently encountered; the right sort will be flowing very slowly down the bark, at source it will be forming a while sticky mass and producing the occasional bubble as it ferments, this is the result of various fungi turning the sap sugar to alcohol, this alcohol is volatile and attracts beetles from a fair distance, its production is temperature dependent and so to find white frothy sap on a hot summer night is about as good as ‘torching’ gets as all sorts of beetles will arrive over the course of a few hours. Lures that mimic sap are

easily produced and work well, they need to be thick so that they do not simply run off the wood, and they need to be alcoholic so that they attract beetles; a sugary mixture of molasses, fruit and beer or rum, or a lure containing fermenting fruit will work very well but these will be discussed elsewhere. A good indication of the presence of beetles is lines of fine wood dust produced as they bore out of the wood, these are easy to spot and will soon become very obvious and committed to memory, new wood-dust trails will indicate freshly-emerged beetles and very soon they will be seen as they emerge from the wood, in this way we have observed species such as Hypulus quercinus (Quensel, 1790), Teredus cylindricus (Olivier, 1790) and Platypus cylindrus (Fabricius, 1792) emerging en-masse from logs in our local park. The presence of numerous emergence holes should always be investigated as predatory beetles such as Tillus elongatus (Linnaeus, 1758), which preys on the saproxylic ptinid Ptilinus pectinicornis (Linnaeus, 1758), or the ant beetle Thanasimus formicarius (Linnaeus, 1758) which is a more general predator, are often searching among holes for prey, and various histerids etc will be found in old insect burrows. Fallen trees are a delight as the canopy can be examined and samples taken from rot holes etc, cut trees and logs are also very worth a look as the sawn surfaces will continue to exude sap for a long time and this will attract a wide variety of beetles in numbers. Conversely there will be small areas or perhaps only a single branch on a single tree that hosts a species, and the more searching that is done the more of these very localized beetles will be found e.g. after many years of searching we found a large colony of Enicmus brevicornis (Mannerheim, 1844) on a decaying alder branch in a heavily shaded area of carr in our local park, this colony has persisted for several years and we have yet to find the species anywhere else by day or night. As an example of the variety of beetles to be found on trees the carabids seem to be an unlikely group, they are abundant on pathways etc. at night but a few species will be found on trees and only rarely elsewhere, among these are Calosoma inquisitor (Linnaeus, 1758), Ocys harpaloides (Audinet-Serville, 1821) and occasionally O. quinquestriatus (Gyllenhal, 1810), Calodromius spilotus (Illiger, 1798), all our species of Dromius Bonelli, 1810 and various Microlestes Schmidt-Göbel, 1846 and Syntomus Hope, 1836 among others. Torching should be simply a matter of non-invasive searching; this will preserve a local site and keep it fit for beetles over many years so that the natural progression of species can be observed. No more need be done than to walk around and examine trunks and low branches by torchlight, the base of trees should not be ignored as many rove beetles and ground beetles that are not associated with trees may be found, and many non-saproxylic beetles will be found on timber as well, either resting or hunting.

In general many of the species found commonly on trees at night are otherwise difficult to find without resorting to destructive methods, and for the beginner more used to going out and sweeping or pitfall trapping etc. by day it will very quickly produce a long list of new species. There are too many species to list individually but the following list of families, along with an estimate of the number of species likely to be found at night, will give some idea of the value of this method of recording.

Carabidae Latreille, 1802. About 15 species on wood, many more around the base of trees.
Histeridae Gyllenhal, 1808. At least 15 species associated with wood and associated nests etc.
Ptiliidae Erichson, 1845. About 20 species regularly recorded from decaying wood and fungi etc.
Leiodidae Fleming, 1821 At least 15 species, mostly fungivores.
Staphylinidae Latreille. 1802 About 170 species associated with wood, fungi and insect and avian nests.
Scirtidae Fleming, 1821. Larvae of Prionocyphon serricornis (Muller, P.J.W., 1821) develop in wet rot-holes.
Eucinetidae Lacordaire, 1857. Larvae develop in fungi.
Clambidae Fischer von Waldheim, 1821. At least 3 species of Clambus Fischer von Waldheim, 1821 develop among decaying wood.
Lucanidae Latreille, 1804 includes 3 saproxylic species.
Scarabaeidae Latreille, 1802. Several chafers, also the naturalized Saprosites mendax (Blackburn, 1892).
Buprestidae Leach, 1815 Melanophila acuminata (De Geer, 1774) at burnt wood, Anthaxia nitidula (Linnaeus, 1758) and ten or so Agrilus Curtis, 1825), although these are mainly diurnal.
Eucnemidae Eschscholtz, 1829. All our species are saproxylic, though diurnal as well as crepuscular and nocturnal.
Throscidae Laporte, 1840. At least Aulonothroscus brevicollis (du Bonvouloir, 1859) is known to develop among bark, adults are largely nocturnal.
Elateridae Leach, 1815. About 30 species are known to develop among wood.
Lycidae Laporte, 1836. Our 4 UK species are saproxylic.
Cantharidae Imhoff, 1856. Our species of Malthininae Kiesenwetter, 1852 develop among bark or decaying wood.
Derodontidae LeConte, 1861. Laricobius erichsoni Rosenhauer, 1846 occurs on Pine.
Dermestidae Latreille, 1804. Species of Dermestes Linnaeus, 1758 in old nests, some other species occur among dry, cobwebby wood.
Bostrichidae Latreille, 1802. Bostrichus capucinus (Linnaeus, 1758) and species of Lyctus Fabricius, 1792 develop in decaying wood.
Ptinidae Latreille, 1802. At least 27 saproxylic species, many nocturnal in decaying wood.
Lymexylidae Fleming, 1821. Both UK species are saproxylic, both diurnal and crepuscular.
Phloiophilidae Kiesenwetter, 1863. Phloiophilus edwardsi Stephens, 1830 on various deciduous trees.
Trogossitidae Latreille, 1802. Three UK species develop in dead wood.
Cleridae Latreille, 1802. Eight species develop in dead wood.
Dasytidae Laporte, 1840. Dasytes species develop in wood, but are mostly diurnal.
Malachiidae Leach, 1815. Various species develop in decaying wood, but are mostly diurnal.
Sphindidae Jacquelin du Val, 1860. Both UK species feed on slime moulds among decaying wood.
Nitidulidae Latreille, 1802. At least thirty species associated with dead wood, many at sap or fungi.
Monotomidae Laporte, 1840. All Rhizophagus Herbst, 1793 are recorded from wood, many will be found at night.
Silvanidae Kirby, 1837. Includes five saproxylic species, most are active on the surface at night.
Cucujidae Latreille, 1802. Includes two saproxylic species, both nocturnal.
Laemophloeidae Ganglbauer, 1899. At least six nocturnal saproxylic species.
Cryptophagidae Kirby, 1826. About twenty species of Cryptophagus Herbst, 1792, Henoticus Thomson, C.G., 1868 and Micrambe Thomson C.G., 1863 are associated with decaying wood, all nocturnal.
Erotylidae Latreille, 1802. With the exception of Cryptophilus integer, all are associated with fungal fruiting bodies.
Biphyllidae LeConte, 1861. Both UK species are associated with fungi on dead wood.
Cerylonidae Billberg, 1820. Our three species of Cerylon Latreille, 1802 are associated with fungi on decaying trees. All nocturnal.
Endomychidae Leach, 1815. Symbiotes latus Redtenbacher, 1847 and Endomychus coccineus (Linnaeus, 1758) are associated with fungi on trees, both are nocturnal.
Corylophidae LeConte, 1852. Several species of Orthoperus Stephens, 1829 occur among decaying wood.
Latridiidae Erichson, 1842. Includes about twenty saproxylic species, all nocturnal.
Mycetophagidae Leach, 1815. About twelve species are associated with dead wood fungi, all nocturnal.
Ciidae Leach in Samouelle, 1819. Our twenty two UK species occur among tree fungi.
Tetratomidae Billberg, 1820. Our four species are all nocturnal and saproxylic.
Melandryidae Leach, 1815. All seventeen UK species are saproxylic and nocturnal.
Mordellidae Latreille, 1802. Includes several species that develop in decaying wood, mostly diurnal but sometimes on trunks at night.
Rhipiphoridae Gemminger, 1870. Our single species is associated with hymenoptera nests, adults are crepuscular.
Zopheridae Solier, 1834. All but one of our thirteen species are saproxylic and all are nocturnal.
Tenebrionidae Latreille, 1802. About twenty of our species are associated with decaying wood.
Oedemeridae Latreille, 1810. All species except for Oedemera Olivier, 1789 develop among decaying wood, several are active at night.
Pythidae Solier, 1834. Includes a single UK species, associated with conifers in the Scottish Highlands.
Pyrochroidae Latreille, 1806. Includes three ‘Cardinal Beetles’, all develop under bark.
Salpingidae Leach, 1815. With the exception of Aglenus brunneus (Gyllenhal, 1813) our eleven UK species are associated with decaying wood, all are nocturnal.
Aderidae Csiki, 1909. Our three UK species are saproxylic and nocturnal.
Scraptiidae Gistel, 1848. While our species develop among decaying wood and bark they are diurnal and only rarely found at night.
Cerambycidae Latreille, 1802. Longhorns are mostly diurnal but several species including Prionus coriarius (Linnaeus, 1758) and Arhopalus rusticus (Linnaeus, 1758) are nocturnal, and several generally diurnal species may be found resting on trunks at night.
Anthribidae Billberg, 1820. At least six of our species are associated with fungi on dead wood and all are nocturnal.
Curculionidae Latreille, 1802. Includes a large number of saproxylic species, especially among Cossoninae Schönherr, 1825 and Cryptorhynchinae Schönherr, 1825. This family now includes the bark beetles, Scolytinae Latreille, 1804 and Platypodinae Shuckard, 1839, and the vast majority of our seventy-odd species are associated with bark and are nocturnal.

This may seem like a bewildering list of beetles but many common and widespread species will occur regularly, and among those to look out for at first are:

Ocys harpaloides

Dromius quadrimaculatus

Abraeus perpusillus

Anisotoma humeralis

Sepedophilus marshami

Scaphidium quadrimaculatum

Atrecus affinis

Quedius dilatatus

Trox scaber

Dorcus parallelopipedus

Sinodendron cylindricum

Melolontha melolontha