NITIDULIDAE Latreille, 1802
This family mostly comprises saproxylic and flower-frequenting species. Several are super abundant and Meligethes aeneus has become one of the most significant crop pests in the world.
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
This is a large family of more than 4500 species in about 350 genera and up to 10 subfamilies (opinions differ), it has a worldwide distribution with the greatest diversity in warmer areas but most subfamilies are well-represented in temperate areas and so a familiarity with our UK list will provide a reasonable insight to the family as a whole. The European fauna includes about 240 species of which about 130 occur in central areas and 90 extend to the UK, by comparison the Nearctic fauna includes about 165 species. Historically the classification has been very fluid and the literature is full of examples of members of other cucujoid families being included but the recent scope, if not settled in lower order classification, seems to be overall stable. From our UK point of view a major change has been the removal of the subfamily Kateretinae Kirby, 1837 and its classification as a distinct family. Cybocephalidae was formerly included as a subfamily but now seems sufficiently distinct to be considered primitive to the nitidulid/kateretid complex. Only two subfamilies have a restricted distribution; Maynipeplinae Kirejtshuk, 1998 from Southeast Asia and Calonecrinae Kirejtshuk, 1982 from central Africa, both groups are monogeneric. Carpophilinae Erichson, 1943 includes 7 genera and more than 70 species; it is a cosmopolitan group with several pest species having been spread by trade. More extensive generic lists will be found but many are now included as subgenera of Carpophilus. Cillaeinae Kirejtshuk & Audisio, 1986 includes 9 genera and about 150 species mostly from tropical and subtropical areas, it was formerly included in Carpophilinae but members differ in the structure of the aedeagus. Amphicrossinae Kirejtshek, 1986 includes about 30 species of the single genus Amphicrossus Erichson, 1843, the greatest diversity is in the Eastern Palaearctic and Oriental regions but species also occur in tropical Africa, Australasia and the Nearctic regions. Meligethinae Thomson, 1859 is a mostly Old World subfamily; the Nearctic fauna including only 10 species of 6 genera, about 800 species are known and historically they were included in 15 genera but following a recent revision in which Meligethes Stephens, 1829 was split into more than 22 new genera this has changed
drastically; with 700 species Meligethes included the majority of the species. The subfamily occurs worldwide but the widest diversity is in Afrotropical, Australasian and Oriental regions and the western Palaearctic region, including the UK, has a rich fauna. All species are anthophagous, occurring within the flowers of a wide range of herbaceous plants, shrubs and trees, adults tend to occur on flowers generally while the larvae are often oligophagous or monophagous. Epuraeinae Kirejtshuk, 1986 includes more than 400 species in 20 genera and two tribes; Epuraeini Kirejtshuk, 1986 12 genera and Taenioncini Kirejtshuk, 1998 with 8 genera. The group is widespread throughout the Old World but only poorly represented in the Americas e.g. the Nearctic fauna includes 32 species of the single genus Epuraea Erichson, 1843. The greatest diversity is in eastern Palaearctic and Oriental regions e.g. Epuraea includes almost 300 species in 17 subgenera, and of the 55 species of the subgenus Micruria Reitter, 1875 most occur in China and Japan while only a single species extends to Europe including the UK. The subgenus Epuraea Erichson, 1843 includes more than 200 species and is almost cosmopolitan. Formerly included within the Carpophilinae, they are distinctive elongate-oval and flattened species associated with a wide range of habitats and include mycetophagous, saprophagous and anthophagous species. The following two subfamilies include the majority of the species and, in temperate regions, display the widest morphological diversity. Cryptarchinae Thomson, 1859 is a relatively small group of >300 species in 16 genera and 4 tribes with a cosmopolitan distribution, they are abundantly distinct and distinguished from the other subfamilies by the following combination of characters: the labrum and frons are fused, the procoxae open, the tegmen without lateral lobes, the vertex bearing one row of stridulatory files and the vertex sometimes expanded over the antennal insertions. The group includes some of the most distinctive species e.g. in the UK the genera Glischrochilus Reitter, 1873 and Pityophagus Shuckard, 1839. Nitidulinae Latreille, 1802 is by far the most diverse subfamily with about 110 genera in 6 tribes and is cosmopolitan in distribution. Distinguished from the previous subfamily by the free labrum and from other subfamilies by the abbreviated elytra which reach at least some way across the propygidium (in Carpophilinae they are much shorter, exposing 2 or 3 tergites), the pygidium lacking impressed lines at the base (Meligethinae) and from Epuraeinae by a combination of morphological characters as well as the (generally) well-sclerotized genitalia-in Epuraea they are only slightly sclerotized.
Members are morphologically very diverse, they range from about 1mm to 20mm in length, although in temperate regions they rarely exceed 5mm, and vary from very elongate or oval and flattened to globose and convex species, many are pubescent and this varies from fine recumbent hairs to stiff and dense erect setae, colouration is generally rather drab but many have red or yellow markings and some are brilliantly coloured and metallic. The dorsal surface is usually finely and uniformly punctured and only a very few have distinct elytral striae or carinae, typically they are evenly convex and lack major structures, tubercles or depressions and in most the elytra are abbreviated leaving various abdominal segments exposed. All possess rather short antennae with a compact and distinct club, and this is often the best clue to the family. The following description covers the family generally-there are exceptions in exotic genera- but our UK fauna is diverse and a familiarity will allow much of the northern temperate fauna (and much else) to be recognized to family level; nitidulids are a diverse group that are difficult to key to the family level or encapsulate within a description but rather straightforward to become familiar with through looking at pictures or a reference collection. Head usually transverse and devoid of major structure; prognathous to moderately declined and with moderately to strongly convex and entire to weakly emarginate eyes, and temples that converge towards the base. Clypeus truncate to emarginate, frontoclypeal suture weakly impressed or absent, and the labrum is free (except in Cryptarchinae), transverse and apically bilobed. Mandibles usually unidentate; lacking dorsal cavities or tubercles but with a well-developed molar and subapical tooth. Mentum transverse and apically emarginate. Apical segment of labial palpi fusiform. Antennae 11-segmented with a short and broad basal segment and well-defined and compact 3-segmented club, usually mounted laterally in front of the eyes, the insertions often concealed by a lateral expansion of the frons. Pronotum transverse to quadrate, only rarely elongate, widest at the middle or towards the base and as broad as the elytra across the shoulders, laterally bordered and often explanate, sometimes very widely so. Pronotal angles usually well-defined; anterior angles often produced forward, posterior angles rounded to slightly acute, basal margin straight, weakly rounded or bisinuate. Surface weakly to strongly convex and without major structure although in many there are basal fovea or weakly depressed or flatted areas. Prosternum about as long as a procoxal cavity, with a well-developed and diverse process, procoxal cavities round or nearly so and closely to widely separated and generally closed although open in Cryptarchinae and Amphicrossinae. Scutellum usually relatively large, flat and apically acute or rounded. Elytra transverse to elongate (up to 2X longer than wide), strongly to weakly rounded laterally and continuously or separately rounded or truncate apically so leaving the at least the pygidium exposed. Epipleurs usually strongly developed towards the base but often incomplete, disc usually randomly punctured but in some with up to 10 punctured striae, but without a scutellary striole, these sometimes alternating with variously developed longitudinal carinae. Hind wings in most cases are well-developed although usually with a reduced venation. Abdomen with 5 free ventrites, the basal 2 subequal in length, intercoxal process acute to broadly rounded and sometimes with curved or angled post-coxal lines. Legs short and robust; procoxae round and variously projecting, mesocoxae transverse and usually broadly separated, metacoxae transverse and widely separated, trocanters exposed and obliquely joined to broad femora and unarmed femora, tibiae moderately to strongly broadened towards the apex; pro- and mesotibiae variously crenulate or toothed externally, in Meligethes the protibial teeth afford excellent identification characters . Tarsi 5-segmented in both sexes; the basal segments usually dilated and setose ventrally, in e.g. Pocadius Erichson, 1843 and Soronia Erichson, 1843 they are simple, the fourth segment almost always the smallest but not enclosed by the lobes of the third., claws simple or with a basal tooth.
Many species are attracted to the sap exuded by trees in response to local damage on areas of otherwise healthy bark, they are attracted by various volatiles and tend to remain for long periods, often feeding in numbers where the sap runs along crevices, and very often several species will be present alongside one another. Otherwise the habits are varied and species will be found under bark, on flowers, especially blossom in the spring, on fruit, decaying fungi, among decaying vegetation or at any fermenting plant tissue and a few (e.g. species of Nitidula Fabricius, 1775 or Omosita Erichson, 1843) occur at carrion. Only a few species have become pests of crops or stored products, they are generally a only a nuisance but large numbers can prove economically damaging because of the adult and larval feeding habits and also because they are recognized as vectors of pathogenic fungi; among the most notorious of these are various Carpophilus and Glischrochilus which occur sporadically among stored fruits etc. the strawberry sap beetle, Stelidota geminata (Say, 1825) and the yellowish-brown sap beetle Epuraea luteolus (Erichson, 1843) attack both dried and growing fruits whereas the dried fruit beetle, Carpophilus hemipterus (Linnaeus, 1758) attacks stored fruit and various Carpophilus attack stored as well as growing grains etc. The small hive beetle, Aethina tumida Murray, 1867, is a destructive pest in honey-bee hives and also ruins stored honey, the destruction is caused by larvae which destroy combs and caps, ruin honey by defacation and leaving discarded moultings etc. and by introducing fungi which may ferment the honey, other species are also becoming invasive in hives but predation is rare among Nitidulids; many fungivorous species have been observed to consume larvae etc. under bark but it is unknown among larvae and among the few known exclusively predatory adults are various Pityophagus Schuckard, 1839 which predate bark-beetle larvae, Cychramtodes murrayi Reitter predates the coccid Cryptes baccatus (Maskell, 1892), and Amphicrossus japonicus Reitter, 1873 breeds in water-filled bamboo stems where it predates mosquito larvae. A very few species are associated with ants and termites.
Our UK fauna includes about 90 species of 15 genera and 5 subfamilies although in many works the Cybocephalidae Jacquelin du Val, 1858 are included as a distinct subfamily. So far as our fauna is concerned they may be distinguished from the superficially-similar Kateretidae by the elytral apex which, in the present family, leaves the pygidium and perhaps the penultimate tergite partially exposed whereas in kateretids at least the terminal two segments are fully exposed, and the antennal club which in kateretids is elongate and loose. Carpophilinae is represented by the very rarely imported Urophorus humeralis (Fabricius, 1798), a pest of stored fruit etc. and 10 species of Carpophilus Stephens, 1830, of which 3 occur only under artificial conditions and a further 4 are only rarely imported; they occur on a very wide range of stored vegetables and fruits, especially where they have started to develop moulds. Three species occur in the wild although only C. marginellus Motschulsky, 1858 is at all likely to be recorded; all are saproxylic and associated with fungi and, occasionally, mouldy fruit. Larvae have sometimes been referred to as predatory on bark beetles but little about their biology in the wild is known. Meligethinae Thomson, C.G., 1859 includes the single European species Pria dulcamarae (Scopoli, 1763) and 36 of the 50 or so European species of Meligethes Stephens, 1829. All are monophagous with larvae developing in unopened buds of various flowers although adults tend to occur on flowers generally. They are univoltine with adults overwintering in soil near to the host. M. aeneus (Fabricius, 1775) is a notorious pest of oilseed rape and other Brassica crops. Many are widespread and common and may be sampled during spring and early summer by sweeping flowers generally; hosts are mainly from the families Cistaceae, Rosaceae, Campanulaceae, Cruciferae, Labiatae, Papilionaceae and Boraginaceae. Epuraeinae Kirejtshuk, 1986 is represented by 20 species of Epuraea Erichson, 1843 although E. melanocephala (Marsham, 1802) will often be found under the genus Micruria Reitter, 1875. Adults may be found in a wide range of situations, at sap, on flowers or among decaying vegetation or bark, but the life-cycles of many are unknown; some occur among coniferous bark and some saproxylics have been observed consuming bark-beetle larvae although these may have been dead and developing mould on which the larvae were feeding, E. aestiva (Linnaeus, 1758) is known to develop in subterranean ant nests and Joy also quotes it as occurring in humble bee nests. Beating or sweeping blossom in the spring will produce a few species in numbers and they will be found when working sap runs and compost etc. Cryptarchinae Thomson, C.G., 1859 includes 3 UK genera; our 2 species of Cryptarcha Shuckard, 1839 occur at sap runs on deciduous trees, Glischrochilus Reitter, 1873 includes 3 large and colourful species which occur at sap or among bark-beetle galleries although through the winter and in the spring and autumn they may be found in numbers among decaying vegetation and fungi. The very distinctive Pityophagus ferrugineus (Linnaeus, 1760) occurs under the bark of coniferous trees. Nitidulinae Latreille, 1802 includes 7 genera and 15 species. Our 4 species of Nitidula Fabricius, 1775 and 3 species of Omosita Erichson, 1843 occur among dry carrion, bones and other decaying organic matter, several have been recorded from occupied bird nests and at least 2; N. bipunctata (Linnaeus, 1758) and O. discoidea (Fabricius, 1775) have been recorded inside where dried meats are stored. Soronia Erichson, 1843 includes 3 UK species although S. oblonga Brisout de Barneville, C., 1863 has only very recently been added to our list and is known from a single specimen, all occur among bark, especially at sap runs, Cossus burrows and among fermenting organic matter, 2 species are widespread and locally common. The rest are associated with various fungi; our 2 species of Pocadius Erichson, 1843 occur in puff balls but may also be found in other dry and powdery fruiting bodies, both are widespread though very local in the south. Cychramus luteus (Fabricius, 1787) is widespread and generally common; it occurs in various fungi but adults visit flowers in the spring and early summer, especially Crataegus blossom and umbels. The widespread though local and rare Thalycra fervida (Olivier, 1790) occurs in hypogean fungi and puff balls. The very rare myrmecophilous species Amphotis marginata (Fabricius, 1781) occurs in the south east of England and is associated the ant Lasius fuliginosus (Latreille, 1798).