PTINIDAE | uk beetles

PTINIDAE Latreille, 1802

Spiderweb Beetles

Wild species of this family are generally either saproxylic or inhabit animal nests. Many others, such as the Death-Watch Beetle, are well-known household pests.

Introduction

This large and morphologically diverse family includes about 3000 sp in 250 genera and 11 subfamilies and occurs worldwide. Although most diverse in tropical regions they are well represented in temperate zones and an outline of the European fauna will give a good idea of the family as a whole; about 400 species occur in the United States and 100 in Canada, the European fauna includes more than 500 species, of which almost 60 extend into the U.K. Ten of the subfamilies occur throughout the Holarctic region as well as much of the world generally. The Alvarenganiellinae Viana & Martinez, 1971 includes a single species, Alvarenganiella seabrai Viana & Martinez, 1971, endemic to the Neotropical region. Historically the group has been treated as 2 distinct families, the Anobiidae Fleming, 1821 which includes all of the species with the exception of the ‘spider beetles’ or Ptinidae. These were combined in 1995 by Lawrence and Newton into the single family Anobiidae, but the earlier name Ptinidae has now been generally adopted for the family.

The following 2 subfamilies have traditionally comprised the Ptinidae:

Gibiinae Jacquelin du Val, 1860 includes 2 tribes, both of which are sometimes included in the Ptininae. Gibiini Jacquelin du Val, 1860 includes 2 genera and 4 species; Gibbium and the monotypic Sulcatogibbium Bellés, 1986, a stored product pest from Mali. Meziini Bellés, 1985 includes 7 genera and about 16 species. They are native to the Palaearctic and African regions but have been introduced widely into other areas; of the 8 species of Mezium Samouelle, 1819 several have become established throughout the New World and Australia (etc.), 3 occur in central Europe and a single species extends to the U.K. Stethomezium Hinton, 1943 includes 3 tropical species, one of which, the Neotropical S. squamosum Hinton, 1943 has been recorded in imported products in the U.K. With the exception of Stethomezium all species are semi-synanthropic, occurring in animal and bird nests or among plant debris as well as among stored products. Members of this subfamily are very distinctive; the antennae are ‘normal’ i.e. filiform and without modified terminal segments, and placed close together on the front of the head. The body is convex and rounded, and beneath the reflexed elytra the meso- and metathorax and abdomen are narrow. Most species are glabrous or nearly so.

POLYPHAGA Emery, 1886

BOSTRICHOIDEA Latreille, 1802

1.5-9mm

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Ptininae Latreille, 1802 is a large subfamily of about 650 species, 4 tribes (although this is not universally accepted) and more than 50 genera. The greatest diversity is in the Palaearctic region with about 400 species, of which 250 are Eurasian, 30 occur in central Europe and about 100 in southern Europe. The New World fauna includes about 200 species of which 70 occur in the United States and 15 in Canada. More than 100 occur in the Australasian region and almost 200 in Africa. . The New Zealand fauna includes 6 species of Ptinus, while that of Madagascar includes 14 species in 6 genera. Several species are pests of stored products and have become truly cosmopolitan e.g. Ptinus tectus Boieldieu, 1856 which occurs on remote islands such as South Georgia and the South Sandwich Islands. Many genera and species are endemic to particular regions e.g. the monotypic Neotropical Bellesus Özdikmen, 2010 or the mostly Madagascan Xylodes Waterhouse, 1876, Tropicoptinus Bellés, 1999 includes 3 species from Columbia and Costa Rica. Compared with many large subfamilies there are few large and naturally widespread genera although Myrmecoptinus Wasman, 1916 occurs throughout Southeast Asia and Australasia and Ptinus Linnaeus, 1767 is a notable exception. The name ‘spider beetles’ refers to the overall appearance of many adults, the compact and convex body and long appendages being suggestive of mites or small spiders, especially so in Gibbium and Mezium (formerly in Ptinidae) but also in other genera such as Tipnus and some Ptinus, Sphaericus and Trigonogenus. The more typical body shape of the family is elongate and rounded or parallel-sided, and flattened. Ectrephini Wasman, 1894 includes 6 genera and about 50 species and is restricted to Australia. Although recognizable as Ptinids they are atypical in having the antennae long, broad and often clubbed or otherwise modified, they are heavily sclerotized and rounded species mostly with a constricted pronotum. Sphaericini Bellés, 1982 includes about 60 species in 5 genera and is cosmopolitan in distribution. Two genera occur 9in the U.K. and both are included in the Ptinini in our 2012 checklist. Sphaericus Wollaston, 1854 includes about 30 species in 4 subgenera and, with the exception of 2 Afrotropical and 2 Australian species, all are Palaearctic. The saproxylic pest species S. gibboides (Boieldieu, 1854), which is native to the Mediterranean region, has been recorded worldwide and is now established in the U.K., New Zealand and the Nearctic region. Trigonogenius Solier, 1894 includes 10 mostly Neotropical species of which one, the Nearctic T. globosus (Solier, 1894), has spread worldwide and is established in the U.K.; in Europe it has been listed as T. globulus (Solier, 1849), which is a distinct species and has not been recorded here. Ptinini Latreille, 1802 includes more than 400 species in 17 genera and is cosmopolitan; the European fauna includes 30 species in 7 genera. Pseudeurostus Heyden, 1906 includes almost 20 Old World species of which the eastern Palaearctic P. hilleri (Reitter, 1877) has been widely recorded in Europe and the Nearctic region. Dignomus Wollaston, 1862 includes more than 60 species and is widespread in the Old World, excepting Australia, including Europe but does not extend to the U.K., similarly the widespread Palaearctic and Afrotropical genus Niptodes Reitter, 1884, with about 20 species, occurs in Europe but not the U.K. Niptus Boieldieu, 1856 includes 15 species and occurs throughout the New World, Afrotropical and Palaearctic regions. N. hololuecus (Faldermann, 1835), native to western Asia but now established in temperate regions worldwide, occurs regularly in the U.K. among stored products. The monotypic Tipnus Thomson, C.G., 1859 includes the Holarctic T. unicolor (Piller & Mitterpacher, 1783) which occurs naturally in the nests of mammals, birds and social insects, has been recorded widely, if sporadically, in the U.K. The majority of species are classified into the large genus Ptinus Linnaeus, 1767; with almost 300 species and well represented in all biogeographical regions it is very typical of much of the subfamily, 13 species are included in the U.K. list.

The remaining subfamilies have traditionally comprised the Anobiidae.

Mesocoelopodinae Mulsant & Rey, 1864 This cosmopolitan group includes about 400 species in 16 genera and 2 tribes which are distinguished by the number of antennal segments; 11 in Mesocoelopodini Mulsant & Rey, 1864 and 10 in Tricorynini White, 1971. Two species of 2 genera included in the former tribe occur in central Europe and both are saproxylic, neither has been recorded in the U.K. Two Neotropical species of Tricorynus Waterhouse, 1849 have been recorded widely in Europe among imported foods but so far not in the U.K. Species are elongate oval with serrate antennae that lack modified terminal segments and are inserted laterally in front of the eyes. The anterior margin of the prosternum is emarginate and the head is hypognathous with the labium and mandibles resting against the prosternum. The anterior margin of the metasternum is straight, not produced towards the mesocoxae as in the Dorcatominae, and the first abdominal sternite has distinct impressions which accommodate the hind legs.
Anobiinae Fleming, 1821 Although generally there are 7 recognized tribes, almost 50 genera and about 400 species the limits and relationships of many genera remain uncertain and about 20 have yet to be placed within tribes. This subfamily includes some of the best known and notorious wood-boring pests of furniture and structural timbers etc. and some of these naturally saproxylic species have been transported far from their natural range e.g. the European native Anobium punctatum (DeGeer, 1774) is now cosmopolitan. Almost all species have greatly elongated terminal antennal segments and are of a rather typical appearance. The head is prognathous with the mouthparts at most only moderately angled down, often partly concealed by the anterior margin of the pronotum, with large but generally only moderately convex eyes and 11-segmented and filiform or, rarely, serrate antennae which are inserted laterally in front of the eyes. Pronotum quadrate to transverse, up to 1.5X wider than long, often widest at distinct posterior angles and narrowed to a curved and smooth anterior margin, sometimes evenly curved laterally and variously explanate. In many the disc is strongly raised from the base and angled; in side view the pronotum and elytra form a distinct angle, and the anterior margin is reflexed laterally so that the base of the head is hidden from above, the head is also partly inserted into the prothorax, sometimes concealing the posterior margin of the eyes. The elytra are generally long, parallel-sided or nearly so, and continuously curved or truncate apically, and with distinct impressed striae. Five tribes occur in central Europe. The Gastrallini White, 1982 is a worldwide group of about 120 species in 4 genera , it is represented in central Europe by 2 species of Gastrallus Jacquelin du Val, 1860, one of which, G. immarginatus (Muller, P.W.J., 1821) also occurs in the U.K. European species are distinct in lacking elytral striae. Stegobiini White, 1982 is a small tribe of 30 species in 6 genera; the distribution is mostly Holarctic although a few species occur in the Neotropical and Oriental regions. Two genera occur in central Europe. The Holarctic Oligomenus Redtenbacher, 1849, with 26 species constitutes most of the tribe and 3 species occur in central Europe but do not extend to the U.K. The single species of Stegobium Motschulsky, 1860, S. panaceum (Linnaeus, 1758), is native to the Mediterranean region but has become a worldwide pest of foodstuffs and has become established in the U.K. Nicobiini White, 1982 includes 3 genera and about 70 species and is cosmopolitan with the exception of Australia. The widespread genus Nicobium LeConte, 1861 includes 5 species of which one, the southeast European N. castaneum (Olivier, 1790) is saproxylic and has become a pest of paper products i.e. books etc. and occasionally occurs in central and northern Europe but not the U.K. Hadrobregmini White, 1982 is a cosmopolitan tribe of 50 species in 7 genera, 2 of which occur in central Europe. Hadrobregmus Thomson, C.G., 1859 includes 15 species and is Holarctic, of the 2 central European species, H. denticollis (Creutzer in Panzer, 1796) extends to the U.K. In Europe H. pertinax (Linnaeus, 1758) is the more common species, extending east to northern China while H. Denticollis has a more restricted, central European distribution and is much more local. Both are saproxylic. Probium Motschulsky, 1845 includes 16 species and occurs throughout the world except for the Afrotropical region, a single species occurs in central Europe but not the U.K. Anobiini Fleming, 1821 is a cosmopolitan group of about 40 species in 6 genera, 4 of which occur in central Europe and 2 in the U.K. Anobium Fabricius, 1775 includes 4 Palaearctic species of which 3 occur in central Europe and 2 in the U.K. A. punctatum, the ‘furniture beetle’ is saproxylic in the wild but is a cosmopolitan pest of processed timber, spread through trade. Hemicoelus LeConte, 1861 is a Holarctic genus of 8 species, 7 occur in the Nearctic region and 4 in central Europe. Two species have been recorded in the U.K., the widespread H. fulvicornis (Sturm, 1837) and the much more local H. canaliculatus (Thomson, C.G., 1863) (=H.nitidus (Herbst, 1793)). All species are saproxylic.
Dorcatominae Thomson, C.G., 1859 this large and cosmopolitan subfamily includes about 700 species in 7 tribes and by far the greatest diversity is in tropical and subtropical regions, in central Europe 2 tribes are represented by about 20 species in 4 genera while in the Nearctic region it is the most speciose subfamily with 11 genera representing 5 tribes. Most species are small, <4mm, but all are distinctive, mostly due to the modified antennae. The body is compact and rounded, moderately elongate or, only in Petalium LeConte, 1861, cylindrical. Antennae inserted laterally in front of the eyes, 11-segmented with one or two basal segments expanded and usually with the last 3 modified; triangular, variously expanded internally or, rarely, parallel-sided or branched. When retracted the antennae lie in prosternal grooves and so are not visible from above although in Calymmaderus Solier, 1894* the terminal segment remains visible beyond the pronotal margin, similarly the legs retract into ventral grooves. The head is hypognathous, at rest the labium and mandibles lie against the prosternum, with moderately convex eyes and long temples. The anterior pronotal angles are weakly produced forward, the anterior prosternal margin is emarginate and the anterior metasternal margin extends forward between the mesocoxae. The pronotum is transverse, broadest at distinct and often acute posterior angles and sinuate along the basal margin. Many species are saproxylic, occurring in decaying timber and, especially, around bracket-fungi, in warmer climates many develop in dry stems of herbaceous plants. Dorcatomini Thomson, C.G., 1859 includes about 200 species in 10 genera of which 3 genera and 14 species occur in central Europe, the U.K. list includes Anitys rubens (Hoffmann, J.J., 1803), 2 species of Caenocara Thomson, C.G., 1859 and 5 species of Dorcatoma Herbst, 1792.
Dryophilinae LeConte, 1861 is a small subfamily of about 100 species in 10 genera and 2 tribes although some genera remain unassigned and variations in the classification will be found. The Ptilineurini Boving, 1927 includes one (or two) Old World genus with 3 species distributed in Southeast Asia and Australia. Of the Dryophilini LeConte, 1861 only a single species, the Australian adventive, Dryophiloides niger Lea, 1924 has been recorded in the Nearctic region. The Majority of species occur in the eastern Palaearctic and Australasian regions and a few are Afrotropical. The tribe is represented in central Europe by 5 species of 3 genera. Homophthalmus Abeille de Perrin, 1875 includes 3 species; one from South Africa and 2 from Europe, H. rugicollis (Mulsant & Rey, 1853) extends north to Germany but not the U.K. The single species of Grynobius Thomson, C.G., 1859 occurs widely through Europe including the U.K. Dryophilus Chevrolat, 1832 includes 10 species and is Palaearctic, 3 species occur in central Europe of which 2 extend to the U.K. The majority of species are saproxylic. They are recognized by the antennae which, at least in our species, have the last 3 segments greatly elongated or enlarged, in the wider fauna some have serrate or pectinate antennae, and the smoothly convex and unmodified pronotum. In appearance they are typical of the family, drab coloured with the head and pronotum narrower than the elongate and rather parallel-sided elytra which have distinct striae.
Eucradinae LeConte, 1861 is a cosmopolitan group including almost 100 species in 8 genera and 2 tribes although some genera have yet to be assigned. The Eucradini LeConte, 1861 includes 3 species of the single genus Eucrada LeConte, 1861 and occurs in Asia and North America. Five genera and about 70 species are considered to belong to the Hedobiini Mulsant & Rey, 1868, and these are distributed mostly in the Palaearctic, Oriental and Afrotropical regions, 4 species of 3 genera occur in the Nearctic. Three species occur in central Europe, the widespread Ptinomorphus imperialis (Linnaeus, 1767) which extends to the U.K., the more southern P. regalis (Duftschmid, 1825), and Hedobia pubescens (Olivier, 1790) which is widespread in southern and central Europe but does not occur in the U.K. Species are typical of the family; elongate, parallel-sided and rather flattened, with filiform or serrate antennae which lack modified terminal segments, and a smoothly convex anterior margin to the pronotum (the posterior half may be sharply raised as in Ptinomorphus) which lacks lateral borders. Our species is very distinctive due to the elytral pattern; the larvae develop in dead wood of a range of broadleaf tree species.
Ernobiinae Pic, 1912 is a large group of more than 150 species in 15 genera and 4 tribes but some genera remain unassigned. They occur throughout the world with the exception of Australia although the African fauna is poor. The greatest diversity is in the Holarctic, particularly the Palaearctic region; about 50 species of 8 genera and 3 tribes occur in the Nearctic and some e.g. the monogeneric Paralobium Fall, 1905 and Parobius White, 1966 are restricted to that area. Three tribes are represented in central Europe. The Ochinini Zahradníc, 2013 is monogeneric, Ochina Dejean, 1821 includes 7 species, most of which are Mediterranean but several extend into central Europe and one. O. ptinoides (Marsham, 1802) occurs in the U.K. Xestobiini White, 1982 includes 3 genera and about 30 species and is Holarctic, 3 species of 2 genera occur in central Europe and it is represented in the U.K. by Xestobium rufovillosum (DeGeer, 1774), the death-watch beetle. Ernobiini Pic, 1912 includes about 100 species in 4 genera and is Holarctic. Two genera occur in central Europe. Episernus Thomson, C.G., 1863 includes 15 species of which 5 occur in central Europe but not the U.K. The majority of species, about 80, are included in Ernobius Thomson C.G., 1859, about 10 occur in central Europe of which 6 are included in the U.K. list. All species are distinctive in appearance; Ochina with serrate and unmodified antennae has a transverse and explanate pronotum and characteristically pubescent elytra, species of Ernobius have the terminal antennal segments greatly elongate, characteristically large eyes, slender legs and randomly punctured and pubescent elytra. All species are saproxylic and may occur by sweeping or trapping although the widespread Ernobius mollis (Linnaeus, 1758) occasionally occurs inside, having been attracted to light.
Ptilininae Latreille, 1802 includes about 60 species in 6 (or 7) genera and 2 tribes although the generic placement within the tribes is far from certain. Phanerochilini Fleutiaux, 1896 includes a single species, Phanerochila boliviensis Fleutiaux, 1896, from Paraguay. Ptilinini Shuckard, 1840 includes the remaining genera. The majority of species, more than 30, are included in the Holarctic genus Ptilinus Geoffroy, 1762, the only species of the tribe to occur in the U.K. is the Palaearctic native P. pectinicornis (Linnaeus, 1758) which has been spread by trade and is established in North America and Australia etc. Several more species occurring outside the Holarctic region have variously been included but are likely to belong to other genera. The genus is most diverse in the Palaearctic region but only 2 species occur in central Europe. Species of Ptilinus are distinctive, elongate and often rather cylindrical, the head prognathous with the mouthparts directed forward or only weakly angled down, wide and convex with large eyes and 11-segmented antennae which are pectinate in the males and serrate in the females. The pronotum is smoothly convex anteriorly and strongly granulate or rugose, the body is strongly constricted between the pronotum and long, parallel elytra. Elytra with distinct rows of punctures and fine pubescence; the interstices finely punctured and variable, from flat or weakly convex to distinctly carinate. Most species of this subfamily are saproxylic and tend to occur in numbers, swarming around the host material in warm weather.
Xyletininae Gistel, 1856. This large and cosmopolitan group includes almost 400 species in 3 tribes, almost 40 genera have been described but at least 20 remain to be assigned and so the tribal limits are likely to change in size and scope in the future. Metholcini Zahradnik, 2009 includes 15 species of the single genus Metholcus Zahradnik, 2009 which occur in Southern Europe and North Africa (Tunisia). Lasiodermini Böving, 1927 includes (at least) 2 genera and more than 100 species, members occur worldwide with the exception of Australia. Megorama Fall, 1905 includes 4 Nearctic and 4 southern European species. The large genus Lasioderma Stephens, 1835 includes at least 90 species although this is likely to change as a large number of new species have recently been described from southern Europe and the Near East, and is almost cosmopolitan with the greatest diversity in the Mediterranean region, only 5 species, of which 2 are adventive, occur in the Nearctic region. Six species occur in central Europe, and the near cosmopolitan stored-product pest, L. serricorne (Fabricius, 1792) occurs in the U.K. Most species develop in herbaceous plants, particularly those of the Asteraceae. Xyletinini Gistel, 1856 includes more than 200 species in 8 genera but other genera are likely to be added. They occur throughout the world except for Australia and are most diverse , with about 125 species, in the Palaearctic region, 40 species of 4 genera occur in the Nearctic while only 3 species occur in North Africa. The central European fauna includes 2 genera. The monogeneric Pseudoptilinus Leiler, 1969 occurs throughout central and North Africa, Asia and Europe north to southern Scandinavia but not the U.K. Xyletinus Latreille, 1809 is the largest genus with more than 130 species distributed throughout the world except for Australia, many occur in old world tropical areas while very few are Neotropical and about 12 occur in North America. At least 35 species occur in Europe, of which about 12 extend to central and northern Europe, and a single species, X. Longitarsis Jansson, 1942 occurs in the U.K. Most are saproxylic but a few exotic species develop in dry mammal dung. Species of this subfamily are typical of the family; elongate oval or (mostly) rather parallel-sided with the pronotum often as wide at the base as the base of the elytra, narrowed anteriorly and smoothly convex or explanate dorsally. The head is usually hypognathous with the labium and mouthparts resting against the prosternum, with serrate to pectinate antennae lacking modified terminal segments. The elytra almost always have distinct striae and are pubescent, in some Xyletinus they are patterned by dense scale-like pubescence. The first abdominal sternite lacks impressions to accommodate the hind legs. The group includes a few attractively coloured species e.g. the bicoloured western Palaearctic Xyletinus ornatus Germar, 1844.

Ecology

Many species are known primarily as household pests and these fall into 2 broad categories based on extensions of their natural behaviour; wood-borers and stored-product pests. Perhaps the best known example is the Death-Watch Beetle, Xestobium rufovillosum (DeGeer, 1974), a wood-borer that infests structural timbers etc., due to its nocturnal method of communication by loud tapping sounds. Xestobium is a wood-borer in the wild and on warm late-spring and summer evenings can be heard among dead trees and fallen timber etc., the basic difference being that the former behaviour contributes to the collapse of buildings whereas the latter is beneficial in helping clear decaying wood. Their larvae tunnel through dry dead wood of various broad-leaved timber and, as development times vary with temperature, moisture and nutritional value, this may be protracted and so early stages may be present even as structural timbers are being fitted to new buildings, on the other hand they may enter buildings as they are attracted to light and then find suitable host material. The other European species X. austriacum Reitter, 1890 develops in coniferous wood, particularly fir and spruce. Some xylophagous species are restricted to a particular host or narrow range of hosts e.g. species of Ernobius Thomsom, C.G., 1859 attack mostly pine, while others attack a range of broadleaf species e.g. Anobium Fabricius, 1775 (a notorious pest of seasoned wood and furniture etc), Oligomerus Redtenbacher, 1849 and Hemicoelus LeConte, 1861. Ptilinus pectinicornis (Linnaeus, 1758) has a narrower range of hosts; Fagus, Populus, Quercus and Salix, and rarely occurs inside whereas Gastrallus immarginatus (Muller, P.W.J., 1821) will attack a very wide range of species. Sometimes species within a genus have different host ranges e.g. Hadrobregmus denticollis (Creutzer in Panzer, 1796) attacks broadleaf trees while H. pertinax (Linnaeus, 1758) will attack both broadleaf as well as conifer trees. Species of Dryophilus Chevrolat, 1832 have diverse hosts; D. pusillus (Gyllenhal, 1808) develops in conifers, D. longicollis (Mulsant & Rey, 1853) choose broadleaf trees while D. anabioides Chevrolat, 1832 develop in the roots and stems of broom. Ochina ptinoides (Marsham, 1802) appears to be monophagous on Hedera. Xylophagous species usually have symbiotic intestinal bacteria which allow this lifestyle. Species of Xyletinus Latreille, 1809 occur under bark etc. but are not xylophagous, rather they feed upon dead insects and organic debris, and many others are fungivores e.g. species of Stegatus Wollaston, 1861 consume mycelia as they bore through decaying wood. Some are associated with fungal fruiting bodies, especially on broadleaf trees e.g. species of Dorcatoma Herbst, 1792 or Anitys rubens (Hoffman, 1803), while species of Caenocara Thomson, C.G., 1859 develop within puffball fungi on timber or on the ground. Adults are attracted to fruiting bodies, especially where these have been damaged, and sampling may produce several species of ptinids from a single sample. In the wild many species develop in herbaceous plants and decaying plant material and when conditions are favourable may produce large populations, this occurs particularly in warmer climates, and when these large populations disperse they will often infect stored agricultural products etc. and be transported along with the host away from their native areas. Over the last century or two many species have thus become worldwide in distribution and attracted notoriety as stored product pests. Many of these are widely polyphagous and adapted to survive in arid conditions or in temperature ranges commonly encountered in food-storage facilities. Thus many of our European pest species will thrive in such conditions e.g. Sphaericus Wollaston, 1854, Trigonogenius Solier, 1849, Niptus Boieldieu, 1856 and Lasioderma Stephens, 1835. Many such pests also occur in the wild in temperate regions e.g. species of Ptinus Linnaeus, 1767 occur in a range of domestic and industrial situations but in the wild are saproxylic, while Tipnus unicolor (Piller & Mitterpacher, 1783) occurs inside but in the wild is found in the nests of mammals, birds and social insects. In temperate regions many, or even most, ptinids are univoltine but under artificial conditions of favourable temperature, humidity and unlimited food many become continuously brooded; we once reared Lasioderma serricorne (Fabricius, 1792) on peanuts, and within a season there were all life stages present in abundance. In warmer parts of the world some species are known to develop in dry herbivore dung. The family includes several genera of obligate myrmecophilous species, in the New World Gnostus Westwood, 1885 and Fabrasia Martinez & Viana, 1965 (both Ptininae) but the majority, about 12 genera, occur in Australia (most genera) and Africa.

Description

Adult ptinids vary in shape from round to elongate and parallel-sided or with separately rounded pronotum and elytra; the majority are variations on Ptinus or Anobium and readily recognized as members of the family, the smallest are about 1mm and the largest over 10mm although no European members reach this length. The dorsal surface varies from convex, almost spherical, to flattened, and most are drab black to testaceous or bicoloured. Most are pubescent and this is generally fine and rather dense and may form distinct longitudinal lines on the pronotum and elytra, and many have elytral patterns formed by contrasting pubescence or scales, as in Ptinomorphus Mulsant & Rey, 1868, and sometimes the entire dorsal surface is covered with dense scale-like pubescence e.g. in species of Tricorynus Waterhouse, 1849. Many species can curl up into a tight seed-like ball with the head fitting closely against the prosternum and anterior mesosternal margin and the appendages withdrawn into the ventral surface. The head is generally visible from above although it may be mostly concealed by a raised or anteriorly produced pronotal margin as seen in species of Lasioderma Stephens, 1835, and is generally proportionally small although there are notable exceptions e.g. the Nearctic desert-living Xeranobium Fall, 1905. The orientation varies from prognathous to hypognathous and in many species the vertex is partly inserted into the prothorax and rather steeply inclined anteriorly, in most the vertex and frons are convex to very convex, the vertex may have weak impressions or tubercles or a raised longitudinal median ridge, a frontoclypeal suture is usually well-impressed and the labrum obvious from in front. The eyes are placed laterally and vary widely from almost flat to (usually) convex and prominent, round or oval to reniform and sometimes emarginate or deeply divided anteriorly, the facets may be fine or coarse and in many the eyes are pubescent. The temples are often not visible, being inserted into the prothorax or strongly contracted behind the eyes and so very short. The maxillary palps are usually small and concealed; they vary in form with the terminal segment cylindrical and pointed to fusiform, expanded or almost securiform. , the mandibles are usually well-developed but only weakly produced forward and so generally not visible from above. Antennae 8-11 segmented with the basal one or two segments enlarged, form variable from simply filiform to serrate or pectinate and often with the terminal segments (usually 3) greatly elongated or otherwise modified e.g. in Dorcatoma Herbst, 1792 and Tricorynus, or forming a distinct club. In some e.g. Ptilinus Geoffroy, 1762, they are sexually dimorphic. The insertions are usually lateral, between the eyes and the mandibles, although in Gibbiinae they are placed close together above the frons. The pronotum is very variable in form; often broadest at distinct posterior angles and narrowed to a rounded anterior margin e.g. in some Xyletinus Latreille, 1809, Anitys Thomson, C.G., 1863 or Dorcatoma, otherwise simply rounded laterally or rounded before a sub-basal constriction, almost always with distinct posterior angles and usually narrower at the base than the elytral base or at most only a little wider e.g. in Stegobium Motschulsky, 1860. The lateral margin is often explanate and sometimes widely so, and smooth to finely crenulate. The surface is generally without sculpture although in many it is strongly raised and distinctly angled in side view, the anterior margin is reflexed laterally so that the head is partly concealed. In some there are smaller lateral elevations, longitudinal furrows or fovea. Punctation and pubescence vary considerably and are sometimes diagnostic within a genus. Prosternum shorter than the pronotum and often with lateral grooves to accommodate the legs and antennae, the mesosternum is usually small and flat and often has a longitudinal furrow or impressions, the metasternum is large and often appears to be fused anteriorly with the mesosternum, generally truncate anteriorly or with a cleft and a longitudinal furrow entire or only in the anterior or posterior half, otherwise wide and smooth and often furrowed for the reception of the legs. The pro-coxal cavities are round or oval and usually closely placed, sometimes with a short and pointed prosternal process which extends to the posterior border, the meso-coxae round and contiguous or nearly so, and the meta-coxae transverse and often widely separated. The scutellum is usually small though distinct, and triangular, rectangular or smoothly rounded. The elytra are mostly elongate and parallel to smoothly rounded and with variously developed epipleura, in some species the epipleura are missing and the lateral margins are strongly reflexed without a distinct border. Most have distinct albeit smoothly rounded and not prominent shoulders and continuously rounded or truncate apices which leave the pygidium exposed. Many species have distinctly impressed and often punctured striae, and punctured or shagreened interstices. The hind wings are usually well-developed, even in flightless species. The abdomen has 5 visible sternites which are either free or partially fused towards the centre, and in some there are lateral grooves for the reception of the hind legs. The legs are very variable but usually long, thin and without distinct teeth or spines, the coxae are prominent and sometimes greatly elongated, the trocantins small and hardly visible but sometimes enlarged and obvious along the base of the coxae, the femora are usually only a little wider than the tibiae but may be long and curved or distinctly clavate. The tibiae are not, or only weakly, expanded towards the apex and lack distinct spurs, in some exotic species e.g. Dasytanobium inaequale Pic, 1902 (Xyletininae) from Brazil the pro-tibiae (and femora) are greatly elongated and curved. Tarsi 5-segmented; the basal segment is usually elongate, the others elongate to transverse or variously lobed, the fourth is often bilobed and partially covers the terminal segment. The claws are usually smooth and lack basal teeth or lobes. The above description is very general and many variations will be found. Perhaps the most atypical members belong to the myrmecophilous New World genus Gnostus Westwood, 1885, here the pronotum is raised medially with deep lateral furrows and the antennae are 3-segmented; the second segment inserted under the basal segment and the terminal segment long and truncate. Species of the New World myrmecophilous genus Fabrasia Martinez & Viana, 1965 have several large teeth on the lateral pronotal margins and greatly enlarged hind tibiae that contain large trichomes.

Larvae

Ptinid larvae are small, at most 10mm when fully grown, pale and generally glabrous or with sparse, scattered setae or lateral pubescence, distinctly pubescent only in Ptininae and Gibbinae. The head is small, darker and free, not or only slightly inserted into the thorax, with small eyes on the lateral margin and short one-segmented antennae that are sometimes hardly visible. The mandibles are well-developed, symmetrical, triangular and sharp. The body is generally curved and the thorax and abdomen are about equal in width with all segments distinct. The legs are short but well-developed. In most there are two distinct dorsal grooves on each segment, the prothorax and abdominal segments 1-8 have a pair of lateral spiracles, and the meso- and metathorax and abdominal segments 1-5 or 8 have well-developed transverse rows of tiny spines on the dorsal surface and also sometimes laterally. The terminal abdominal segment is generally rounded, without distinct spines or urogomphi.