Anobium Fabricius, 1775

Suborder:

Superfamily: 

Family:      

Subfamily:

Species:

POLYPHAGA Emery, 1886

BOSTRICHOIDEA Latreille, 1802

PTINIDAE Latreille, 1802

ANOBIINAE Fleming, 1821

A. inexspectatum Lohse, 1954

A. punctatum (De Geer, 1774)

This is a small old-world genus of wood boring beetles, about 20 species are described and most of these occur in warmer parts of the world but four are native to the Palaearctic region, one of these is restricted to Spain while the others are widespread across Europe, and one of these, A. punctatum (De Geer, 1774), the notorious furniture beetle, has become established in many countries worldwide through the trade in timber. Species vary from widely polyphagous, as with the furniture beetle, to monophagous, as with two of the European species, A. inexspectatum Lohse, 1954 and A. hederae Ihssen, 1949, which both occur on ivy. They are typical of many northern temperate saproxylic species with a single generation each year, larvae developing through the summer, overwintering, and completing their development and pupating in the spring to produce new-generation adults in late spring and summer, although the furniture beetle may be continuously brooded under artificial conditions. Furniture beetles may appear indoors at any time although they often disperse in numbers during the summer and may appear on walls or windows, they are otherwise easily sampled by sweeping foliage of older trees, especially in woodland or parkland where there is a good supply of timber in various stages of decay, they have been recorded from a very wide range of both hard and soft woods, including ivy-which is unfortunate for the coleopterist as our other species, A. inexspectatum, is restricted to that host plant.

The general appearance of Anobium, parallel-sided and convex with a highly vaulted pronotum and very elongate terminal antennomeres will soon become familiar. Specific identification can be very difficult but the form of the antennae will place specimens within the correct subfamily and, within the limited UK fauna, generic placement is straightforward.  Genera within the Anobiini Fleming, 1821 can be very difficult to separate but the use of underside characters greatly simplifies this. In Hadrobregmus Thomson, C.G., 1859 and Priobium Motschulsky, 1845 the basal abdominal sternites are fused about the middle and lack the distinct sutures seen in Anobium. In Hemicoelus

Anobium inexspectatum 1

Anobium inexspectatum 1

Anobium punctatum 1

Anobium punctatum 1

Anobium inexspectatum 2

Anobium inexspectatum 2

Anobium punctatum 2

Anobium punctatum 2

LeConte, 1861 the pronotal elevation is less developed and the pygidium is rounded with a central tooth, in Anobium males the pygidium is acuminate while in females it is rounded with a median emargination. Our other genera are distinct; Stegobium Motschulsky, 1860 lacks the pronotal elevation, and species of Gastrallus Jacquelin du Val, 1860 lack the strongly punctured striae seen in Anobium. Several characters are useful in separating our species e.g. in male A. punctatum the three apical antennomeres are much longer than those of male inexspectatum, they are also more slender and the inner margin is less strongly curved-the penultimate segment often being distinctly angled towards the apex, in series this difference can be very obvious but alone it is difficult to appreciate, and no such difference exists between females. Colouration is too variable in each case to be useful. In series the species look different at low magnifications; A. punctatum is has rougher, more strongly sculptured elytra and the elytral pubescence is more strongly oblique around the scutellum and forms more regular lines, but these features vary and are not reliable. Freshly-eclosed specimens which are pale in colour occur throughout the season, as do older specimens with worn elytral pubescence and so specific identification should be based on the form of the metasternum and the pygidium. In doubtful cases males are easily separated by the form of the aedeagus; in inexspectatum the median lobe is elongate and lanceolate, almost pointed at the apex, and extends well beyond the parameres, whereas in punctatum it is widely dilated towards the apex, broadly rounded and not, or hardly, longer than the parameres.

Anobium punctatum (De Geer, 1774)

The Furniture Beetle

More generally known simply as ‘woodworm’ this is a major pest of wooden furniture and structural and decorative timber; it attacks all kinds of wooden goods and wickerwork etc and may form serious infestations long before any adults are seen. Adults do not feed and it is the larvae that do the damage, varnished and treated wood tends to be safe from attack but as larvae can take several years to develop they may survive any treatment and persist through manufacturing processes, the first sign of attack is usually small holes, about 2mm in diameter, formed when adults bore out of the wood, these are usually accompanied by small piles or streaks of very fine wood dust that becomes darkened with age. Woodworm is usually introduced in to houses with old furniture etc and may spread when adults emerge and disperse by flight, this is usually at night and as they are attracted to lights they may occur on walls or around windows in numbers. Larvae vary in their rates of development and there may be dispersing adults while the larval infestation continues to damage their host material, it can therefore be very persistent and difficult to eradicate, especially as infestation often occur under floorboards or in lofts and may spread widely before they are discovered. This species occurs throughout the Palaearctic region north to Iceland and far beyond the Arctic Circle in Scandinavia, it is present across North Africa and the Middle East and has become established in many countries worldwide through accidental introductions, in the UK it is abundant across Wales and the south of England but more local and scarce further north. Adults occur mostly through spring and summer in woodland and wooded pasture etc, they attack a wide range of dead and decaying broadleaved and coniferous trees and usually infest wood that is damp, they mate in the spring and females lay up to thirty eggs in bark crevices, cracked wood or old exit holes, often on the wood from which they emerge; they may be observed on the surface of old trees at night but are easily sampled by sweeping foliage at any time. Larvae emerge within two to four weeks and immediately bore straight down into the xylem where they feed and produce random and often dense galleries; infestation in structural timber may be so dense that the wood turns to a fragile structure of dust and borings that easily crumbles but this is rarely seen in the wild. Larval development depends upon temperature, moisture and starch content and the type or density of the wood; in the wild the species is very probably univoltine but under artificial conditions, in dry hardwood it takes at least two years and often much longer. Fully-grown larvae burrow towards the surface but do not emerge, they construct a chamber just beneath the surface in which they will pupate and adults emerge

shortly afterwards by biting a hole through the top of the chamber. Eggs are tiny, creamy or yellowish in colour and very difficult to find among crevices in wood, and fresh larvae are also very inconspicuous but when fully grown they measure up to 7mm, are soft-bodied and creamy-white with a dark-brown and well-sclerotized head and have short yellowish hairs across the body. Adults emerging in the wild are strongly attracted to lights from houses etc and will fly into windows in the summer and find unfinished wood to attack, it seems that they prefer processed wood or perhaps they may simply thrive under artificial conditions through the general absence of natural predators and diseases, thus the species has become synanthropic and is generally much more common in artificial environments-this despite the enormous range of DIT chemicals and traps as well as specialist companies available to eradicate them.

2.4-5.0mm. Mature specimens vary from black to pale brown, usually with the appendages a little lighter. Head hidden from above under the anterior pronotal margin, Frons broad and flat between large, weakly convex and glabrous eyes, antennae inserted anteriorly in front of the eyes and separated by a little more than the length of the basal segment. Three terminal antennomeres very long; 9 and 10 expanded internally, the terminal segment almost symmetrical, these much longer in males compared to females. Pronotum broadest in the basal fifth and narrowed and rounded anteriorly (from above), in side view highly vaulted in the basal third and declined in almost straight lines rounded anterior angles and slightly acute posterior angles, lateral margin bordered throughout. Metathorax with a deep longitudinal impression extending behind the middle and basal abdominal sternites with complete and distinct sutures. Male pygidium broadly rounded, female pygidium truncated and weakly emarginate. Elytra elongate, with broadly-rounded shoulders and continuously rounded apical margin, striae strongly punctured and complete almost to the apex, interstices flat or very weakly convex; compare with inexspectatum a little more roughly sculptured and with the pubescence around the scutellum more strongly oblique. Legs long and slender, femora without ventral teeth, tibiae without obvious spurs and tarsi 5-segmented,  the basal and apical segments simple and longer than the others, and segments 2-4 weakly lobed.

Anobium inexspectatum Lohse, 1954

This very local and generally scarce species has a very restricted western European distribution from Spain to Austria and Slovenia and north to the Netherlands and the UK, but it is difficult to separate from several closely similar species and, as there are records from North West (European) Russia, it may be much more widespread than is currently supposed. It was only recognized as a British species in the 1970s but since that time it has found to be widespread and locally common across south east England and East Anglia and more local throughout Wales and south and central England. Adults occur through the summer and are exclusively associated with old ivy although on the continent they are thought to occur on some broadleaf trees such as oak (Quercus L.), they may be beaten from ivy foliage and usually occur in numbers but they disperse nocturnally by flight and also occur interception traps. Little is known of the biology but larvae bore into old thick ivy stems and are likely to overwinter in their galleries, complete their development in the spring and pupate in a cell near the surface of the xylem.  Fresh adults may be found in galleries in the spring but will need to be looked for very carefully as they play dead when disturbed and may remain motionless for long periods-the name Anobium means ‘lifeless’.

2.1-4.1mm. Elongate and parallel-sided, the pronotum with a characteristic raised surface, entirely pale to mid-brown, usually with the appendages paler. Head completely hidden from above, with large spherical and glabrous eyes, and wide and flat between the antennal insertions, antennae 11-segmented  with the last three segments very elongate and variously curved along the internal margin (the relative lengths of the three apical segments varies slightly and is not a reliable guide to the sex of a specimen). Pronotum from above broadest across the base and rounded anteriorly, the posterior angle distinct and acute-the specimen may need to be manipulated to appreciate this-in side view the anterior angles are rounded and near-perpendicular and the dorsal surface is strongly raised, highest behind the middle and narrowed in more-or-less straight lines to the anterior and posterior margins, the lateral margins are bordered throughout and the surface is finely punctured and pubescent. Elytra transversely convex, with rounded shoulders and almost parallel-sided to a continuously curved apical margin, striae strongly punctured and extending almost to the apex, interstices with dense, fine recumbent pubescence; this runs longitudinally except around the scutellum where it is moderately-at less than 45°-oblique. Very similar to A. punctatum but the metathorax lacks the deep longitudinal impression which extends beyond the middle towards the apical margin in that species. The sexes may be distinguished by the form of the pygidium; acuminate with a weak apical emargination in males and rounded and slightly emarginate in females.

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