COSSONINAE Schönherr, 1825
The majority of species are very local and rare, only Euophryum confine is at all common. Species are mostly saproxylic and occur in a variety of habitats.
By weevil standards this is a rather modest group of about 1700 described species included in 275 genera and 19 tribes although many more species await description and the limits of the various groups are not fully understood; they are generally recognized by the external apical margin of the front tibiae being produced into a curved tooth or hook, the presence of series of cleaning setae on the inner-margin of the front tibiae, usually close to the apex, and a series of distinct hypostomal (beneath the mouthparts) setae, and there are other features e.g. a long pharyngeal process on the mandibles, that may be unique to the group but more work needs to be done. They are very similar to the Molytinae and many feature overlap although so far as our UK fauna is concerned they are generally distinct on gross morphology, and they have often been placed near to Scolytinae and Platypodinae (no doubt encouraged by the saproxylic lifestyle of many species) or Dryophthorinae, and occasionally near to Entiminae or Curculioninae. The group occurs worldwide and is most diverse in warmer regions, most tribes and genera have rather restricted distributions, especially in tropical regions, but both northern and southern temperate regions have diverse faunas; the Palaearctic region includes 11 tribes and about 80 genera while 5 tribes and more than 30 genera are represented in the Nearctic region (although this discrepancy is at least partly explained by the different systems of classification used.) Many species are associated with decaying wood and this lifestyle has facilitated the spread of many by trade and some genera are now almost cosmopolitan in distribution, on the other hand many are monophagous or oligophagous and so limited by the distribution of their host plants e.g. the Araucariini Kuschel, 1966 includes 5 genera which are associated with various Araucariaceae and so restricted to parts of South America and Australasia although it is tantalizing to imagine that species associated with the monkey-puzzle tree in Chile might appear in the UK where the host is a common ornamental plant. Many islands worldwide have associated endemic species and these include most of the Atlantic islands off Europe and Africa as well as Madagascar and the Galapagos etc. but the tropical Atlantic island of St Helena is hot-spot for the subfamily with 17 endemic genera. The UK fauna includes 16 species of 13 genera included in 6 tribes. Several of our genera have a Holarctic distribution and a few extend further south while a few species have become cosmopolitan with the trade in timber etc, one of the best-known examples being Euophryum confine, the New Zealand Wood Weevil, which is now established and widespread across the western Palaearctic and Nearctic regions and has been recorded widely across the world. The Palaearctic fauna includes the following tribes which demonstrate the level of familiarity with the group, at least in Europe, and the complex nature of the classification.
ACAMPTINI LECONTE, 1876 is a small tribe of 8 genera which are generally restricted to various regions worldwide e.g. Acamptus LeConte, 1876 is a New World genus while the Palaearctic fauna is represented by 3 species of 2 genera which are restricted to Nepal. The group is relatively poorly understood and includes some island endemics which may represent further genera.
ALLOMORPHINI FOLWACZNY, 1978 is a monotypic tribe; the single species Allomorphus franzi Folwaczny, 1968 has so far only been found in Austria.
APHYLLURINI VOSS, 1955 is also monotypic and includes the single species Aphyllura brenskei Reitter, 1884 which is endemic to Germany.
CHOERORHININI FOLWACZNY, 1973 includes 4 species of the single genus Choerorhinus Fairmaire, 1858; 2 are endemic to Japan, a further species is endemic to Afghanistan and one is widespread, C. squalidus Fairmaire, 1858 occurs across Europe including Germany and France, North Africa and Asia Minor but, maybe surprisingly, has not become established in the UK.
Worldwide the COSSONINI Schoenherr, 1825 includes 17 genera, the Palaearctic fauna includes about 55 species in 14 genera and the greatest diversity is in the east e.g. 5 genera including a total of 7 species are endemic to Japan, and 2 genera, Pseudocossonus Wollaston, 1873 (6 spp.) and Phloeophagosoma Wollaston, 1873 (8 spp.) occur in China and Japan. Several other genera are restricted to Asia but the North African fauna is also comparatively diverse; the monotypic Micromesites Pic, 1920 and the 2 species of Marvaldiella Alonso-Zarazaga & Lyal, 1999 are very localized whereas 5 of the 6 species of Rhopalomesites Wollaston, 1873 are endemic to various Atlantic islands, Madeira and Tenerife etc, a further species R. tardii (Curtis, 1825), which occurs on the Azores, is more widespread and extends to the UK where it is widespread though very local and generally rare. The European fauna otherwise includes species of the following 2 genera although a third, the monotypic Phloeophagiodes Abeille de Perrin, 1895, is endemic to France. Species of Cossonus Clairville, 1798 occur throughout the Holarctic area; about 20 occur in the Nearctic region and 10 are Palaearctic but only 3 occur in Europe and of these 2 extend to the UK; C. parallelepipedus (Herbst, 1795) is a very widespread European species while C. linearis also extends into Asia, both are very local insects of southern England. Mesites Schönherr, 1838 is also Holarctic although the 2 Nearctic species are likely to be adventive, the Palaearctic fauna includes 9 species of 2 subgenera; one, with 5 species is North African while the other, with 4 species, is Eurasian but none occur in the UK.
DRYOTRIBINI LeConte, 1876 is a large group of about 45 genera with the greatest diversity in warmer regions worldwide, it is Holarctic and includes 25 genera and about 75 Palaearctic species which are most diverse in Europe and North Africa e.g. 7 species of Hajekia Colonnelli, 2014 are known from Yemen, and 12 species of Caulotrupis Wollaston, 1854 occur in Morocco, otherwise most species are of fairly restricted distribution e.g. the 17 species of Amaurorhinus Fairmaire, 1860 are mostly endemic to France and Italy. Only a single native European species occurs in the UK, the widespread western European Cotaster uncipes (Boheman, 1838) is known from a single site in Oxfordshire and was almost certainly introduced with plants from the continent. A further species, Allopentarthrum elumbe (Boheman, 1838) , thought to be native to Africa but now inhabiting tropical forests around the world, has been found under artificial conditions at a single UK site and is no doubt introduced.
NEUMATORINI Folwaczny, 1973 includes 4 species of the single genus Neumatora Normand, 1920; 3 are endemic to Tunisia and a further species occurs in Italy.
ONYCHOLIPINI Wollaston, 1873 is a Holarctic group which extends into tropical regions worldwide, it includes 22 genera of which 15 occur in the Palaearctic region and are represented by about 62 species. The tribe is generally distributed and well-represented across the region although many species have a limited distribution in Europe, central Asia and North Africa, and less than 10 are widespread in Europe or Europe and western Asia. Three species occur locally in the UK; Stereocorynes truncorum (Germar, 1824) is a very widespread European species that extends into Asia Minor and India, Pseudophloeophagus truncorum (Stephens, 1832) has a more limited, western European and northwest African distribution, and Pselactus spadix (Herbst, 1795) occurs throughout Europe, North Africa and extends into Asia Minor, it has also become widely established by trade e.g. in Australia and North and South America.
PENTARTHRINI Lacordaire, 1865 is a large cosmopolitan group including more 50 genera, it is most diverse in warmer regions and only poorly represented in northern temperate zones; the Palaearctic fauna includes 13 species of 8 genera although Euophryum Broun, 1909, with 2 widespread European species, is introduced from New Zealand. The only other widespread European species is Pentarthrum huttoni Wollaston, 1854; this is thought to be native to South America and now established through much of North America and Europe, including the UK. The remainder are all local eastern Asian or Oriental species. Stenotrupis marshalli Zimmerman, 1938, a probably widespread) tropical species, occurs under artificial conditions at a single UK locality.
PROECINI Voss, 1956 is a mostly tropical group of 14 genera and only 10 species of 4 genera extend into the Palaearctic region, of these only 2 species of the single genus Conarthrus Wollaston, 1873 occur in Europe; both are very local but the Australian introduction, C. littoralis (Broun. 1880) occurs at a few coastal sites in the UK. A further species, the Southeast Asian C. praeustus (Boheman in Schoenherr, 1838), occurs under artificial conditions at a single UK site.
RHYNCOLINI Gistel, 1848 is the largest Palaearctic tribe; it includes 3 subtribes and is by far most diverse in warmer regions. Phloeophagina Voss, 1955 includes 3 genera and is Holarctic. The monotypic Muschanella Folwaczny, 1964 is endemic to China, but Melicius Alonso-Zarazaga, 2002, with 9 Palaearctic species most of which are of very restricted distribution, includes 2 very widespread European species but neither occur in the UK. The Holarctic genus Phloeophagus Schoenherr, 1838 includes 6 Palaearctic species; all occur in Europe and 3 are widespread with one, P. lignarius (Marsham, 1802), extending to the UK. Pseudomimina Voss, 1939 includes 6 genera of which only one is Palaearctic but does not occur in Europe. Rhyncholina Gistel, 1848 includes about 40 genera and occurs worldwide, 33 species of 7 genera occur in the Palaearctic region but most are of limited distribution and many are restricted to eastern parts of Asia, but Rhyncolus Germar, 1817, which includes about 14 species and is predominantly European, includes 6 widespread species and one of these, R. ater (Linnaeus, 1758) extends north into the UK. A further 15 species of this genus occur in North America.
So far as the European fauna is concerned the species are generally saproxylic; associated with decaying trees and fallen timber, often where fungus infestations are present, where the larvae develop as they bore through damp wood although a few e.g. Cotaster uncipes (Boheman, 1838) are more generally associated with decaying leaf-litter in woodland situations. More generally they are associated with a very wide range of plant products in all biotopes from arid or even desert regions to humid rainforests or maritime habitats; they infest both living and dead plant material, in the case of Euophryum confine also attacking processed wood e.g. plywood and fibreboard in domestic and other artificial situations as well as infesting a wide range broadleaf and conifer trees in the wild. They develop in all types of plants from healthy herbaceous or woody plants to decaying wood or leafy material, rootstocks, seeds, ferns and hanging dry palm fronds, cacti, fruits and nuts; some are monophagous or oligophagous while it is likely that the majority are polyphagous, the condition of the host material being more important than the species, especially regarding its age, state of decay or the presence of fungal infection. Most temperate species are nocturnal and active about the host material during the warmer months, with a few exceptions, notably Euophryum, they do not form aggregations like many other weevils and they tend to occur in small numbers, although this is not true of species from warmer climates. Mating occurs on the surface of host material during the spring and summer and females lay single eggs in bark crevices or among other material, they are generally not so fecund as many weevils and tend to lay small numbers of large eggs; females of some species will gnaw into host material in order to deposit eggs and some exotic species have been observed boring into wood in order to oviposit, much like bark beetles, and in such cases the adults may remain until the larvae emerge. Adults may be sampled by searching at night or be sieving the products of wood decay and associated fungi but they tend to occur rather randomly and so aroma trapping or other types of sampling methods would be needed to target specific species.
Regarding the UK fauna only Euophryum confine is likely to be encountered on a regular basis, and this only in England and Wales, our other member of the genus, E. rufum (Broun, 1880) is a very local and rare species in England and Wales, both occur year-round; confine is synanthropic and often found on window sills etc. in numbers, both are associated with a range of host trees in various stages of decay. Pselactus spadix (Herbst, 1795) is associated with decaying processed wood but is unusual in being restricted to coastal habitats in Wales and southern England. Pentarthrun huttoni Wollaston, 1854 is associated with decaying and fungoid timber in buildings. Our other species are associated with decaying trees, mostly broadleaf but sometimes, as with Rhyncolus ater, conifers as well. Three species listed as British are introductions from tropical regions and are known only from the Eden Project biomes.
Members of this subfamily are mostly small beetles, our UK species range from 1.6-12mm but more generally from 1.5 to 12.5mm, they are narrow, elongate and flattened and in most the pronotum and elytra are separately rounded, or the pronotum is rounded while the elytra are parallel-sided, and the vast majority are drab, from pale to dark brown or black, and while many are glabrous or nearly so the dorsal pubescence is very variable and several genera e.g. Acamptus or Himatium include densely pubescent or scaled species. The head is visible from above and, with the forwardly-projecting rostrum, lies in the same plane as the body, the vertex is simply convex between usually large, round and often prominent eyes and the surface is variously punctured. Rostrum very variable; usually elongate and sometimes very much so although in some it is severely reduced (in which case they strongly resemble Scolytinae, broad to very narrow and often expanded apically. Some exotic litter-dwelling species are eyeless. The clypeus is fused to the frons and the labrum is absent, scrobes vary from missing to deep and well-developed, antennae geniculate with the scape usually longer then the funiculus which varies from 5- to 7-segmented, club very variable in shape but usually with sutures plainly visible. In most the antennae are short and relatively thick and inserted near the middle of the rostrum, either near to the apical dilation or in the basal half, sometimes e.g. in Rhopalomesites or Mesites, on a small tooth-like swelling. Pronotum quadrate to elongate and weakly to strongly rounded laterally, only rarely e.g. in Allopentarthrum, almost straight, distal and basal margins straight or weakly curved, sometimes the basal margin is weakly bisinuate, and lateral margins without, or with only weakly-developed, borders, surface weakly convex to almost flat, without structure but in some with a variously developed medial impression, punctation in most well-developed; strong and moderately dense. Prosternum variable but usually long in front of circular and well separated coxae, the process complete but not overlapping the mesosternum, the apex truncate to circular. Mesosternum usually flat and relatively narrow with widely spaced and usually round coxal cavities, metasternum long and flat to moderately convex, with moderately to widely separated coxae which are weakly to very strongly transverse and almost reach the elytral epipleura. Scutellum well-developed and usually obvious, generally level with the elytra and sometimes convex or only visible towards the base. Elytra very slightly transverse to very elongate; up to three times longer than wide, and always longer than the pronotum, sometimes three times the length, basal margin straight or weakly curved to follow the pronotal base, shoulders well-developed and distinctly angled to sloping and indistinct, usually about as wide as the maximum width of the pronotum, lateral margins weakly curved or parallel-sided to a continuously-rounded apex. Basal elytral margin with or without a raised bead, epipleura absent or only present towards the base, each with 10 variously-developed rows of punctures, these are usually quite strong and form distinct striae but in some they may be confused and vary in size, interstices flat to strongly convex and variously punctured or carinate, in some with alternate interstices raised and prominent over the declivity, often with tubercles towards the apex and in some with small teeth on the declivity much in the style of some Scolytinae. In most the elytra are glabrous or only very finely and hardly noticeably pubescent but there are many exceptions; the Nearctic Acamptus echinus Casey, 1892 is a splendid example, it has dense recumbent scales to the head, pronotum and elytra as well as rows of erect broad and truncate scales to the interstices, more modestly species of Himatium Wollaston, 1873 have dense scales to the head and pronotum and lines of recumbent scales to the interstices. In many the elytra are slightly explanate around the declivity, this flange may be distinct and visible from above, as in Euophryum, and may also be asymmetric with the left side more developed than the right. Hind wings usually fully-developed. Abdomen with five ventrites, the basal two connate; all ventrites smooth and simply punctured; never with teeth or tubercles and never excavate. Legs short and robust; pro-coxae round and projecting, mesocoxae round or nearly so and flat to weakly projecting, metacoxae variously transverse and usually flat, trochanters well-developed and obliquely attached to the femora, femora variously flattened and lacking a ventral tooth, tibiae broadened to a truncate apex, at most with only small spines externally, outer margin produced apically into hook-like tooth which is usually strongly developed, inner apical angle with a small spine. Tarsi 5-segmented; basal segment shorter than the following 2 combined, third segment variously bilobed and sometimes hiding the small fourth segment, terminal segment long, often as long as the other segments combined.