Elateridae | UK | Ukbeetles

ELATERIDAE Leach, 1815

Click Beetles

So named for their ability to jump with a distinctive 'click' sound, this very diverse group includes many abundant species which are likely to be found in most habitats.

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POLYPHAGA Emery, 1886

ELATEROIDEA Leach, 1815

1.5-21mm

Introduction

This is a large and cosmopolitan family of about 10000 species in 400 genera and 17 subfamilies, depending upon how some of the groups e.g. Subprotelaterinae Fleutiaux, 1920 or Thylacosterninae Fleutiaux, 1920 are defined, and the modern definition includes some groups formerly regarded as distinct families e.g. Drilini. From some of the examples given below it will be obvious that the family is in a state of flux and that modern molecular techniques are changing the already somewhat fluid state of the classification, both within the family and with regard to other closely related families, and that any system of subfamilies etc, is only going to be temporary. The common name refers to the audible ‘click’ they produce when jumping into the air, they do this from an inverted position by rapidly forcing the Prosternal process into a cavity in the mesosternum, the purpose of which is to escape predators or simply to right themselves when upside down. All elaterids can perform this click as can some eucnemids but here it is much less powerful and any jumping produced tends to be feeble by comparison. The greatest diversity is in tropical regions where they often display brilliant and sometimes metallic colours and patterns; some are bioluminescent and some may reach 75mm in length. Adults inhabit a wide range of biotopes; the majority of temperate species are occur in woodland or wooded environments although many also occur in open situations; grassland, steppes and agricultural situations etc., some are associated with wetland habitats e.g. Actenicerus sjaelandicus (Muller, O.F., 1764) and many species worldwide occur at altitudes up to the alpine zone. Adults of most species are short-lived and have a correspondingly short season although during this time they may be locally very common; spring and summer are the best times to sample them. Many temperate species are diurnal but there are some common and widespread species that will only be found nocturnally e.g. Athous campyloides Newman, 1833 is active after dark on trunks and logs in open situations, and Stenagostus rhombeus (Olivier, 1790) will occasionally be found by sweeping foliage or flowers but on summer evenings as the light fades they may be seen in flight, often in numbers, around wooded borders. Adult elaterids should be searched for among foliage and on the flowers of trees, shrubs and herbaceous plants, by sweeping all kinds of grassland, under bark or among accumulated wood debris in tree hollows,

especially when these are exposed after strong winds, leaf litter and tussocks may be very productive in the winter as may be flood refuse, or under logs and stones or among gravel. Adults of many species will occur at light or flight interception traps in wooded areas, and both diurnal and nocturnal species are attracted to fermenting fruit and beer traps. Some species e.g. Elater ferrugineus Linnaeus, 1758 have been surveyed using pheromones. Adults generally are phytophagous, consuming tender buds and young leaves, flower parts, nectar and pollen etc. but many also consume other insects and their larvae or eggs, or even dead insects and it is thought that females of the majority of species consume food of animal origin before ovipositing. Some species are long-lived and overwinter under bark etc. as adults, and in such species mating occurs early in the year soon after they become active. Species overwintering as larvae, which generally occurs underground, appear later in the spring and mate in early summer. The life cycle of many temperate species takes a year or two but this varies depending upon temperature etc. and a four year cycle is not uncommon.

Description

Although there is great diversity in the family the general form of the adults will quickly be appreciated and recognized, both in the field and in specimens or from pictures. The elongate form etc. is also displayed by some eucnemids, sometimes so closely that they are almost indistinguishable, and this is certainly the case with the world fauna; there has been much shuffling of groups between the families in the past and some are still assigned tentatively. In general the eccentric placement of the second antennomere upon the first will distinguish eucmenids. Similarly some throscids have a similar body form but here the antennae are clubbed.

The body form is generally convex, usually slender to broadly oval and tapering or rounded towards the apex, the largest European species is Paracalais parreissi (Laibner, 2000) and the largest of all are species of the African genus Tetralobus Lepeletier & Serville, 1828. The majority of temperate species are below 20mm while the longest U.K. species is Stenagostus rhombeus (Olivier, 1790) at 21mm. The colouration is generally drab; black to pale brown and sometimes with various red to yellow markings and some are metallic, in tropical regions there are many vividly coloured and beautiful species and some are bioluminescent with pale markings to the pronotum or the elytra indicating the source of the light. Many species are pubescent, generally finely so on the dorsal surface, and this may be dark or pale, sometimes forming patterns on the elytra. Some have scales e.g. Agrypnus Eschscholtz, 1829 and these often form striking colour patterns. Most species are punctured dorsally with various punctation to the head and pronotum and punctured striae on the elytra. The cuticle is often reticulate or variously microsculptured and has very fine micropunctures which may be granulate. The head is retracted into the thorax, usually to about the posterior margin of the eyes, and prognathous or, rarely, hypognathous, and convex, as in Agriotes Eschscholtz, 1829 or flat, as in Athous Eschscholtz, 1829. The vertex is very variable but often bears longitudinal carina or other surface structures, the frontoclypeal suture is absent and the labrum is free. The clypeus forms an angle with the frons and is sometimes bilobed, the two parts being divided by a longitudinal keel. The eyes are generally large and protruding with small facets. The biting mandibles are well-sclerotized and either pointed or divided into various apical teeth and the base has a brush of dense hairs, they are proportionally small and mostly hidden under the labrum. The antennae are inserted under the elevated lateral margin of the frons in front of the eyes, they are generally 11-segmented but have 12 , and may be simply filiform, serrate , pectinate or bipectinate, or flabellate. The pronotum is generally elongate to quadrate and convex, sloping down to a flattened posterior margin and with strong impressions towards the base. The dorsal surface may be strongly sculpted or impressed e.g. in the Nearctic genus Pityobius LeConte, 1853, or the Neotropical Balgus Fleutiaux, 1920. The hind angles are variously produced and often have a ridge or ridges along the dorsal surface of the extensions. Punctation is random; the size and spacing varies and a mixture of sizes may be present. The lateral margins are usually simple, without teeth or serrations etc. but see e.g. semiotinae, and straight or sinuate; narrowing from the hind angles to the anterior margin. The promesothoracic ‘click’ mechanism is generally well-developed; the Prosternal process extending behind the procoxae and fitting into a deep mesocoxal cavity, the anterior margin of the process is usually produced forward to form a variously reflexed mentum. The notosternal sutures are complete, well-impressed or grooved and form lateral antennal cavities. The procoxal cavities are separate and the coxae do not project below the prosternum. The hind wings are usually well-developed and most species are strong fliers. The abdomen has 5 ventrites, the first four being fused. The elytra completely cover the abdomen, have well-developed humeri and 9 usually punctured and impressed striae although this varies and some may be present as a row of punctures or, especially the lateral striae, may be missing altogether. Interstices vary from flat to very convex, in temperate species they are at most only weakly convex, they sometimes have keels and are variously microsculptured; transversely rugose, reticulate, tuberculate and usually very finely punctured. They are usually of equal width although this varies and in some, e.g. species of Agriotes, wider and narrower interstices may alternate. Deflexed epipleura are present at least basally and extend variously along the lateral edge, the apices may be completely or separately rounded, truncate, sinuate or with one or two spines, or they may be produced individually or as a pair into a point. The aedeagus is trilobed; the parameres often with apical hooks. The legs are

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Sexual dimorphism in Anostirus castaneus (Müller, O.F., 1764)

generally proportionally long and either slender or robust; the pro- and mesocoxae are round and globose and the metacoxae transverse, flat and mostly hidden under expanded femoral plates. Tarsi 5-5-5; the segments often simple, variously lobed and sometimes with ventral pubescent pads. The claws are either simple, toothed at the base or serrate, and a short empodium bears apical setae.

Sexual Dimorphism

Most temperate species do not show specific differences but when placed in series it is often obvious that females are more convex, longer and broader so that the outline is a little more rounded, and the antennae are often shorter. Sometimes the elytra are relatively broader posteriorly in the female e.g. in many Agriotes, the head and pronotum may be more transverse e.g. in some Cidnopus, or the hind angles of the pronotum may be shorter e.g. in Anostirus. In many there are differences in the antennal segments e.g. in Ctenicera where the female has serrate segments and the male pectinate. In some species the sexes are differently coloured e.g. in Sericus brunneus (Linnaeus, 1758) the female has a patterned pronotum whereas the male is unicolourous. Many species show differences between the sexes in various abdominal structures.

Larvae

Elaterid larvae are phytophagous or predaceous, or a mixture of both, and live in decaying wood, leaf-litter, insect nests and among roots underground. The majority of species develop over two years and in general they are considered beneficial as many feed on plant pests e.g. species of Athous Eschscholtz, 1829, Dalopius Eschscholtz, 1829 and Stenagostus Thomson, C.G., 1859 etc. Species of Selatosomus Stephens, 1830 and Prosternon Latreille, 1834 predate sawfly larvae and pupae but their effect is probably insignificant as predation rates are low and they are not considered suitable as biocontrol agents. Some species, however, are serious pests of agricultural crops and ornamental grass etc. In arboriculture the larvae of Ectinus aterrimus (Linnaeus, 1761) develop in beech seeds and acorns in central Europe and outbreaks of adults are controlled with pheromone traps. Larvae of the predominant pest species develop underground and are known as wire-worms, they include species of Athous, Agriotes, Melanotus and Adrastus, and they may take from 3 to 5 years, depending upon conditions, before they are fully grown. They can destroy areas of perennial grass in parkland and gardens etc. and they infest a wide range of crops including potato and beet tubers, corn, wheat, maize and strawberry as well as rapidly growing crops like lettuce and spinach. They also

Athous haemorrhoidalis (Fabricius, 1801) larvae

http://data.nhm.ac.uk/dataset/collection-specimens

carry and spread bacterial and viral diseases between plants. As few as 5 larvae per metre can reduce crop yield by 5%. During the early stages of plant growth they damage or destroy seeds and consume emerging radicals and cotyledons, then as the larvae grow they continue to feed upon the roots. They locate plants by following carbon dioxide gradients in the soil, their cylindrical shape allowing them to move quickly and they readily utilize pre-existing burrows to move between plants. Outbreaks are controlled by deep ploughing and crop rotation but pesticides are used against serious infestations although the larvae are known to have a remarkable ability to recover from insecticide exposure. Applying insecticides to the soil in strips between crops has proved effective, as have poison-baited plants, pheromone traps and parasitic fungi. The occurrence of some species depends upon soil type and climatic conditions. Adults of many species feed on fresh foliage, stems and flower buds and can become pests when large populations develop as has happened with some species of Athous among cereal crops on the continent. Elaterid larvae are long and slender, parallel-sided and either cylindrical or flattened; most are shiny and smooth but some have prominent tubercles, specialized setae or transverse carina on the body segments and many are finely pubescent. The head is prognathous with the labrum fused to the anterior edge of the frontoclypeal plate so forming a median and variously toothed projection. Antennae 3-segmented with a convex swelling on the second segment, the mandibles symmetrical, variously toothed and lacking ventral lobes. The thoracic segments have sclerotized plates dorsally and ventrally. The legs are 5-segmented including a claw-like pretarsus. The terminal abdominal segment is often produced and angled down and serves in locomotion, the form is very variable; in some e.g. Agriotes Eschscholtz, 1829, Dalopius Eschscholtz, 1829 and Melanotus Eschscholtz, 1829 it is pointed whereas in e.g. Selatosomus Stephens, 1830 and Cidnopus Thomson, C.G., 1859 it is bifid due to a deep caudal notch.

Classification

It has been very difficult to find a general consensus on the subdivisions of the Elateridae and so what follows is a brief description of the major groups that are generally considered to be valid.

AGRYPNINAE Candéze, 1857

The size of this subfamily has changed over recent decades as many genera have been transferred to the Adelocerini Candéze, 1857 (Pyrophorinae). On the other hand the Pyrophorini Candéze, 1863 is sometimes included as a tribe of the Agrypninae. In the narrow ‘modern’ sense the subfamily includes 9 tribes and more than 1000 species. The group is dominated by the cosmopolitan genus Agrypnus Eschscholtz, 1829 with about 500 species, more than 60 of which are Palaearctic but only 2 occur in Europe, the northern Mediterranean A. crenicollis (Ménétriés, 1832) and A. murinus (Linnaeus, 1758) which is widespread including the U.K. The widest diversity is in tropical and sub-tropical regions although they are relatively poorly represented in the Neotropics. Most members of the subfamily are either covered with scales or have dorsal patterns produced by scales. They are mostly robust and broadly-oval species with relatively short antennae which are serrate from the fourth segment .The Prosternal suture is modified into a deep antennal groove and the mid-coxal cavity is closed by the mesosternum and the metasternum. The tarsal claws have at least one hair at the base. Adults occur under bark, among wood pulp or leaf litter and among vegetation generally although many prefer open grassland, scrub or dunes. Many are crepuscular or nocturnal and may be found by sweeping at any time of the day or night. In general little is known of their biology but larvae of many are known to occur under bark or among decaying wood, under stones or debris, among leaf litter or in the soil among roots and some are known to be predaceous. Many feed on the roots of various plants including grasses, and some damage crops e.g. larvae of the Australasian Agrypnus variabilis (Candéze, 1857), known as the sugarcane wireworm, feeds on the roots of various crops but especially sugarcane, damaging seeds and consuming radicals and emerging leaves, they sometimes occur in huge numbers and then are controlled by insecticides. One group deserves attention; the genus Alaus Eschscholtz, 1829 includes more than 20 species of large elaterids, 25-45mm long, distributed throughout the New World and Australasia and known as Eyed click beetles or Eyespot beetles. They are so called because of their striking circular pronotal maculae. Adults are mostly crepuscular and may occur at light in large numbers, they feed on nectar and sap etc. while the larvae are predatory in decaying wood. They pupate underground and adults occur from April to June in temperate regions. Other striking species may be found among the Hemirhipini Candéze, 1857, a group including 21 genera and more than 450 species. Species of Lycoreus Candéze, 1857 are spectacular e.g. L. corpulentus Candéze, 1889, the one-eyed Madagascan click beetle or L. goudti (Laporte de Castelnau, 1836). The tribe also includes the genus Calais Laporte de Castelnau, 1836 with more than 70 species, some of which occur in southern Europe; see the African species C. tortrix (Candéze), commonly known as the Harlequin click beetle. Following recent research this subfamily now includes the very atypical elaterid group Drilini Blanchard, 1845, which inludes the British Drilus flavescens (Fourcroy, 1785).

CARDIOPHORINAE Candéze, 1859

This is a large and cosmopolitan subfamily including at least 1100 described species in 40 genera and 2 tribes although the validity of these is questionable; the Nyctorini Semenov & Pjatakora, 1936 includes the single genus Nyctor Semenov & Pjatakora, 1936 and is often considered synonymous with the Cardiophorini Candéze, 1860. Most species occur in tropical Africa; about 120 species in 5 genera are Nearctic while 7 genera are Palaearctic of which 3 occur in central Europe. The least diverse region is Australia. Many species are localized to areas of sandy soils or ancient woodland and so are rare or threatened although only one, Cardiophorus gramineus Scopoli, 1763 is protected in Europe. The adults can be abundant in sandy or desert regions and can occur in huge numbers at light traps, they frequent flowers and are considered important pollinators in some regions. The larvae are very distinctive with a slender and cylindrical body and peculiar externally toothed mandibles and for this reason many are considered to be predacious although the Nearctic Horistonotus uhleri (Horn, 1871), known as the sand wireworm, is known to be a serious pest in the eastern United States, feeding upon the roots of a wide range of crop species. Most develop in areas with sandy soils, often in wooded situations, and some are saproxylic. Adults are characterized by the longitudinally convex head with steeply declined mouthparts and the convex frons which has the anterior margin entire. The pronotum is wrinkled along the base, the prosternal process short, truncate anteriorly and raised above the coxae. The Prosternal suture is closed anteriorly and margined by a narrow line. The scutellum is cordate. The claws are sometimes denticulate but never have setae at the base.

The U.K. fauna is very poor with 4 species of Cardiophorus Eschscholtz, 1829 and a single species of Dicronychus Brullé, 1832. Cardiophorus is the largest genus in the subfamily with more than 600 species; more than 210, all in the nominate subgenus, occur in the Palaearctic of which about 60 are European. Two species occur in the U.K: C. assellus Erichson, 1840 is very local and mostly coastal in southern England and Wales, and there are a few coastal records from Devon, Cornwall and south Wales of C. vestigialis Erichson, 1840. A further 2 species are included in our checklist but are either of very doubtful occurrence or are long extinct: C. gramineus (Scopoli, 1763) was listed by Stephens in 1830 with a few scattered records from England, and C. ruficollis (Linnaeus, 1758) was listed by Stephens in 1830 as occurring in London and Norfolk. There have been no records of either since that time. Dicronychus includes about 40 Palaearctic species of which about 20 occur in Europe, D. equisetioides Lohse, 1976 occurs very locally around the north Devon and Somerset and south Wales coasts.

DENTICOLLINAE Stein & Weise, 1887

This is a cosmopolitan and very large group of about 2000 species included in 9 tribes and more than 230 genera. Five tribes are represented in the Palaearctic region of which four are European and two occur in the U.K. The widest diversity is in the Asian and Oriental regions. They vary considerably in detail e.g. the protruding eyes of Denticollis or the developed antennae of Ctenicera but overall they are typical elaterids; mostly drab although there are many metallic species, elongate, fusiform and variously convex and most species are to some extent, some densely so, pubescent. Distinct from two of the other large subfamilies, Elaterinae and Melanotinae, by the prognathous and flat head with mouthparts at most only weakly declined. From the Hypnoidinae they are distinguished by the mesepisternum bordering, or very nearly bordering, the coxal cavity; in the Hypnoidinae they are well separated. Their ecology is very diverse with many root-feeders and pest species, saproxylics as well as species with more specific requirements such as wetlands or woodlands. Beyond this generalization most groups must be considered separately as there is much overlap with other groups, especially the Elaterinae. The classification will be found to vary, even among recent authors. The U.K. fauna is fairly representative of the group and includes the following tribes:

Ctenicerini Fleutiaux, 1936

Actenicerus Kiesenwetter, 1858 is a Holarctic genus of about 30 species, more than 20 are Palaearctic and of these one occurs in the U.K. Anostirus Thomson, C.G., 1859 includes about 40 Palaearctic species and several more from Asia, a single species occurs in the U.K. Ctenicera Latreille, 1829 is a widespread Holarctic, Afrotropical and Australian genus with 9 Palaearctic species. Two occur in the U.K. Calambus Thomson, C.G., 1859 includes a single widespread Palaearctic species. Aplotarsus Stephens, 1830 includes 8 Palaearctic species and of these 2 are Holarctic. Three species are European of which 2 occur in the U.K. Paraphotistus Kishii, 1966 includes about 20 Palaearctic species of which two occur in the U.K. Prosternon Latreille, 1834 includes 8 Palaearctic and 6 Nearctic species. A single species occurs in the U.K. Selatosomus Stephens, 1830 is a Holarctic and Oriental group of about 70 species classified into five subgenera of which 4 are Palaearctic and another is Nearctic. Three species occur in the U.K.

Denticollini Stein & Weise, 1877

The genus Denticollis Piller & Mitterpacher, 1783 is sometimes considered to be the only genus of this tribe. It contains four Nearctic and more than 30 Palaearctic species. A single species occurs in the U.K. Cidnopus Thomson, C.G., 1859 is a Holarctic genus containing 18 species, 7 are European of which one occurs in the U.K. Kibunea Kishii, 1966 Includes the Eurasian K. minuta (Linnaeus, 1758), which occurs in the U.K., and 3 species in Japan. Limoniscus Reitter, 1905 includes 5 Palaearctic species of which 2 occur in Europe and one is listed as British, The Violet Click Beetle. Athous Eschscholtz, 1829 is a very large Holarctic, Oriental and Neotropical genus with about 300 species in 10 subgenera; 5 species of 3 subgenera occur in the U.K.

Hemicrepidiini Champion, 1894

Diacanthous Reitter, 1905 is Holarctic with 7 species. Only a single species occurs in Europe, including the U.K. Stenagostus Thomson, C.G., 1859 includes 10 Palaearctic species; 2 occur in Europe and a single species in the U.K. Hemicrepidius Germar, 1839 is Holarctic and Neotropical in distribution; 34 species are Holarctic and 22 occur in the Palaearctic region. Of the 4 European species, one occurs in the U.K.

Denticollis linearis (Linnaeus, 1758)

ELATERINAE Leach, 1815

This is a large and cosmopolitan group of more than 3000 species included in 9 tribes and about 200 genera with the greatest diversity in Oriental and Neotropical regions. About 330 species of 20 genera and 4 tribes occur in the Nearctic region and of the 8 tribes and 60 Palaearctic genera 7 tribes and 22 genera are European; the U.K. fauna comprises 11 genera and about 30 species in 5 tribes and includes some of our most common e.g. Agriotes Eschscholtz, 1829, and impressive species e.g. Elater Linnaeus, 1758. The group is, as ever, undergoing extensive taxonomic revision and is very likely to change both in detail and extent. They are very typical ‘click beetles’ with a long and relatively straight or only weakly curved outline and convex or only weakly flattened dorsal and ventral surfaces. Dorsal pubescence tends to be fine and regular and many are strikingly coloured although with a few exceptions the U.K. fauna is rather drab in this respect. The dorsal surface is generally smooth or only moderately granulate or tuberculate and lacks any major structural modification. The head is mostly prognathous to opisthognathous with the vertex convex and the mouthparts directed downwards, the clypeus is either separated from the frons and articulated, or it is fused to the frons which forms two strong lateral keels. The mesocoxal cavity is bordered by the mesepimeron, mesosternum and metasternum, the mesepisternum touching the anteriolateral margin. The margins of the longitudinal mesosternal groove, which may be only poorly developed, are either level with the cuticle or raised above it. The anterior mesonotal margin is emarginate anteriorly. Among the European fauna only Synaptus and Adrastus have pectinate claws. The biology of the group is typical of the family with many saproxylic and subterranean developing species. The following is a brief look at the U.K. fauna. Adrastus Eschscholtz, 1829 is a Palaearctic genus of about 25 species; of the 20 European species 2 extend to the U.K. They occur among vegetation in the spring and have root-feeding larvae. The monotypic Palaearctic Synaptus Eschscholtz, 1829 occurs locally in southern England and Wales in wetland marginal environments. The large and mostly Holarctic genus Agriotes Eschscholtz, 1829 includes more than 150 species of which 30 occur in Europe and 6 extend to the U.K. The larvae are root-feeders and some species are agricultural pests. Dalopius marginatus (Linnaeus, 1758) is the only European member of a Holarctic genus of about 65 species, it is widespread and common in the U.K. Ampedus Dejean, 1833 is a cosmopolitan genus of about 330 species in many, not always well-defined, subgenera, about 65 species of 2 subgenera occur in Europe and 13 species are British. Most occur in woodland environments with larvae developing in decaying wood or under bark etc. Identification is often very difficult and new species are constantly being added, not always sensibly. Brachygonus du Bysson, 1912 includes 5 Palaearctic species of which one, B. ruficeps (Mulsant & Guillebeau, 1855) has been recorded from a single Berkshire locality. Of the 5 Palaearctic species of Ischnodes Germar, 1844, I. sanguinicollis (Panzer, 1793) is British; it is a local and rare insect occurring in southeast England. Megapenthes Kiesenwetter, 1858 is a cosmopolitan genus of more than 200 species and of the 7 Palaearctic species only one occurs in Europe including the U.K., the saproxylic M. lugens (Redtenbacher. 1842). The Palaearctic and Oriental Procraerus Reitter, 1905 includes 15 species, 2 of which occur in Europe and one, P. tibialis (Boisduval & Lacordaire, 1835) is a rare saproxylic species of southern England. Elater Linnaeus, 1758 includes 50 species and is almost cosmopolitan; 3 occur in North America and of the 7 Palaearctic species only is European, extending to the U.K. The greatest diversity is in the Oriental region. The Holarctic genus Sericus Eschscholtz, 1825 includes 9 species of which 4 are Palaearctic and one, S. brunneus (Linnaeus, 1758) occurs in the U.K. Panspaeus guttatus Sharp, 1877 is a recent introduction from New Zealand to the U.K. it is known from a few sites in Surrey and there is a single record from Cornwall.

Elater ferrugineus Linnaeus, 1758

HEMIOPINAE Fleutiaux, 1941

This is a small group of three genera of Asian and Oriental beetles. Included are 15 species of Hemiops Castelnau, 1833, 6 species of Parhemiops Candéze, 1878 and 3 species of Plectrosternum Lacordaire, 1857.

MOROSTOMINAE Dolin, 2000

A small group Including 26 species in 8 genera, all of which are endemic to Madagascar. All are quite distinctive due to the well-developed maxillary and labial palps; in some cases these are very elongate and thickened, see e.g. the genus Mocquerysia Fleutiaux, 1899, or species of Diplophoenicus Candéze, 1895 which have 12-segmented flabellate antennae.

MELANOTINAE Candéze, 1859

This is a large group of about 400 species included in 10 genera occurring throughout the world with the exception of the Neotropical region, the greatest diversity is in the Oriental region and only two genera occur in the Palaearctic of which only Melanotus Eschscholtz, 1829 occurs in central and northern Europe. The group is sometimes included in the Elaterinae with Melanotus is included in the subtribe Melanotina Candéze, 1859 of the Ampedini Fleutiaux, 1947. Melanotus includes the majority of the members with more than 300 described species distributed throughout the Holarctic, Oriental and Afrotropical regions; 50 occur in the United States and about 20 are recorded from Europe. They are either saproxylic or develop in the soil feeding upon roots etc. and some species are serious crop pests e.g. M. communis Gyllenhal, 1817 occurs throughout the world wherever corn crops are grown and in the United States it is a serious pest of corn, sugarcane, sweet potato and sorghum etc. Adults of Melanotus are often large and drab, black to brown and distinctly pubescent. The anterior margin of the frons is entire and the mouthparts are steeply declined forward, the antennae are serrate from the fourth segment. The pronotum is wrinkled along the base and has distinct ridges above the produced hind angles; the Prosternal process is narrowed apically and inclined towards the body posterior to the coxae. The Prosternal sutures are wide, weakly curved at the centre and deepened anteriorly. Claws pectinate. The group is represented in the U.K. by 3 species of Melanotus although M. castanipes (Paykull, 1800) has only recently been separated from M. villous (Geoffroy in Fourcroy, 1785). M. castanipes and M. villosus are widespread, occurring in decaying wood and under bark throughout the year and on flowers in the summer. M. punctolineatus (Pelerin, 1829) is a very local species of southeast England, developing at the roots of grasses etc. in sandy situations.

NEGASTRIINAE Nakame & Kishii, 1856

Includes about 400 species in 2 tribes and more than 25 genera and there are many more waiting to be described, especially from tropical and sub-tropical areas. With the exception of Australia they occur worldwide; there are about 150 Palaearctic species in 15 genera, and 35 species in 8 genera occur in the United States. The U.K. fauna is relatively small with 7 species included in 4 genera. Many develop in wetland situations and some occur at high latitudes and altitudes. The almost worldwide genus Zorochrus Thomson, C.G., 1859 includes more than 100 species, 50 of which are Palaearctic and 2 occur in the U.K. they are small, mostly wetland species whose larvae develop in marginal sand and gravel or among vegetation or roots etc. Most are broadly oval and drab, often with pale markings to the elytra. The 40 or so Holarctic and Oriental species of Quasimus Des Gozis, 1886 are unusual among the group in having randomly punctured elytra rather than striae. The tribe is distinguished among the family by the following combination of characters. The frons is entire, not notched, and the mouthparts project forward and down. Antennae serrate. Pronotum oval with the margins smooth, never cordate, and the base lacking impressions. The Prosternal process is long and narrow, and the Prosternal sutures arcuate. Mesepimeron and mesepisternum separated from the mesocoxae by the meso- and metasternum. Claws simple or only feebly toothed or flanged, and without basal setae.

PITYOBIINAE Hyslop, 1917

Before being raised to the subfamily level this group was included as a tribe of the Dendrometrinae Gistel, 1848, but following modern molecular analysis it is now considered as a tribe of the Denticollinae. It Includes 20 species in 8 genera, distributed through Australasia and the New World. All are saproxylic with predatory larvae. Two species of Pityobius occur in the United States including P. anguinus LeConte, 1853, known as the Bipectinate Click Beetle, a reference to the antennal structure. Some genera e.g. the Australian Parablax (Schwarz, 1906) include strikingly coloured species. Definitely worth a look.

PYROPHORINAE Candéze, 1863

In the widest sense this subfamily includes 10 tribes but it is often considered to consist of only the following tribe. The Pyrophorini Candéze includes about 20 genera distributed throughout the Neotropical and the southern Nearctic regions, all of which are bioluminescent. They are typical elaterids, resembling Athous etc. but with pale light-emitting macula above and below the pronotal hind angles, although these may also extend along the lateral margins, and one under the abdomen. When glowing the light is continuous, unlike some lampyrids which can ‘flash’, and the intensity can be controlled by the beetle; increasing when they are alarmed or handled. All the early stages are also luminescent. Adults feed on pollen and nectar etc. and also, to a lesser extent, other insects and they are diurnal as well as nocturnal. Eggs are laid in the soil and the larvae feed on plant roots, litter and other insects. Most species develop slowly over several years and pupate in the ground. The larvae of the Brazilian Pyrophorus nyctophanus Germar, 1841 develop in tunnels near the surface of termite mounds, emerging on to the surface at night for two weeks during the summer in order to attract the dispersing alate termites as they swarm around the mound, these are collected and stored below the surface as a food source.

SEMIOTINAE Jacobson, 1913

According to modern molecular analysis this group is now classified as a tribe of the Denticollinae but we refer to it here as a distinct group because this is how it is referred to in the literature generally. This is a Neotropical group including 2 genera of unmistakable and often strikingly beautiful elaterids. All are elongate with a sharply acuminate elytral apex, elongate pronotum and variously serrate antennae. The size varies from less than 10mm to about 50mm and many have vivid longitudinal streaks of colour on a pale or dark metallic ground. Semiotus Eschscholtz, 1829 contains more than 80 species and is distinguished by the presence of anteriolateral spines on the pronotum; these may be only weakly defined or the margin may be simply sinuate. Semiotinus Pjatakowa, 1941 includes 17 species, 15 of which have been transferred from the previous genus, which are separated by the straight pronotal margin. The species are saproxylic with predatory larvae living among decaying wood etc. Many are known from only a few specimens. The website of the South Dakota State University includes a page of excellent pictures of both remarkable genera, and the monograph by Wells (Wells, S.A., 2007 Revision of the Neotropical Click Beetle genus Semiotus Eschscholtz) includes a large amount of information as well as excellent pictures of these stunning insects. Must see.

SUBPROTELATERINAE Fleutiaux, 1920

This small group includes 5 species of Subprotelater Fleutiaux, 1920 distributed in Northern Australia and various islands north to Japan. They were formerly included in the Eucnemidae and the placement is still doubtful; they are unusual in having antennal grooves along the sides of the pronotal hypomera, as in some Eucnemids, but have a sclerotized and exposed labrum and the fifth abdominal ventrite is free, as in elaterids. The second antennomere seems to be placed centrally upon the first, as in elaterids rather than eucnemids. They are rather small, 4-8.5mm, drab insects with various pale marking to the elytra, and typical of members of either family.

THYLACOSTERNINAE Fleutiaux, 1920

Includes about 45 species within 5 genera but the placement and limits are still to be settled and the group is variously included in the Eucnemidae. All species are tropical; Cussolenis Fleutiaux, 1920 species are Asian and Australasian, Lumumbaia Muona & Vahlera, 2009 are African and Pterotarsus Guérin-Meneville, 1831, Thylacosternus Bonvouloir, 1875 and Balgus Fleutiaux, 1920 are Neotropical. All are intensely interesting; some Balgus species are bioluminescent, emitting light from the thorax while some Cossolenis superficially resemble huge scolytids and some Balgus have very developed tubercles to the pronotum and elytra. Most species have a very unusual antennal structure, sometimes with a distinct scape and distal segments widely pectinate.

CEBRIONIDAE Latreille, 1802

The Cebrionidae Latreille, 1802 was variously classified as a distinct subfamily of the Elateridae but following modern molecular analysis it is now included as two tribes of the Elaterinae; Cebrionini and Aplastini. Depending upon how the group is delimited it now includes about 200 species in 20 genera with the vast majority included in Cebrio Olivier, 1790. With the exception of Australasia they have a worldwide distribution. These are generally broadly elongate beetles with posteriorly produced pronotal hind angles and 11-segmented antennae which may be simply filiform, serrate or pectinate, and prominent curved and sharply-pointed mandibles. Many superficially resemble Melandryids or Tenebrionids. Most species occur in tropical regions, the Neotropics being especially diverse, where the males are often attracted to light. Several species of Cebrio occur in Southern Europe and all seem to be localized e.g. C. brevicornis Olivier, 1790 from Italy or C. nigricollis Laporte, 1838 from Turkey. C. gigas (Fabricius, 1787) occurs in Spain, France and Italy, and for a long time only males were found, females live underground and come to the surface only in the autumn in order to mate.