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Cerambycidae · ūsuočiai

  • longhorn beetles, long-horned beetles, longicorns
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Most of the text below is from now defunct site www.ukbeetles.co.uk, where it was published under a CC BY 4.0 License.

Around the World

This is one of the largest families of the Coleoptera with about 35000 described species in 4000 genera and ten subfamilies, but the classification remains fluid because each subfamily varies widely and there are generally species in each group which defy the overall description, and this applies even at the family level. They are a very diverse group but in general, with due acknowledgment to the families outlined at the end of this page, they are recognizable. It is also a family where the life history of many species is understood, firstly because many are reared by collectors from samples of host material taken from the field and kept indoors, and secondly because many of the members are pest species of commercially important plant products, especially timber, and so research into their biology receives regular funding. Thus cerambycid faunas tend to be rather dynamic because of the worldwide movement of timber etc. and in many temperate areas the ‘occasionally imported’ list is lengthy compared with that of many other groups. The family is cosmopolitan, occurring from sea-level to about 4000 m and in a very wide range of habitats although in temperate regions they are generally insects of wooded areas. They range in size from a few millimetres to some of the largest species of Coleoptera; the Titan beetle, Titanus giganteus (Linnaeus, 1771), a Neotropical Prionid, is generally considered the largest, if not the heaviest, at up to 16.7 cm. The world’s longest species in absolute terms i.e. including the antennae is the New Guinea species Batocerus kibleri (Schwarzer, 1925) the antennae of which can measure 20 cm. Most cerambycids are between 8 and 50 mm and vary in form from cylindrical to flat, and from elongate to short-oval and broad. Many species worldwide are dull-brown or black but bright, and often very spectacular. Cryptic or mimetic colouration is common and many are metallic, even in temperate regions. Many species are crepuscular or nocturnal and cryptically coloured while, probably the great majority, are diurnal and exhibit a very wide range of colours and patterns; and some exhibit mimicry of ants, bees and wasps, in colour, morphology and behaviour. Ostensibly the defining feature of the group are the long antennae which are generally at least half as long as the body but usually much longer, sometimes ridiculously so, and in general they are longer in the male; though seemingly unwieldy, even the longest antennae are delicate and versatile organs, and this can only be appreciated by observing such species as the Timberman, Acanthocinus aedilis (Linnaeus, 1758) in the wild.

Ecology

Cerambycids are mostly xylophagous and phytophagous and are associated with a very wide range of plants; in temperate regions mostly trees but more generally grasses, including bamboo, herbaceous plants, cacti and succulents. The larvae develop within all parts of the host; leaves, twigs and branches, seeds, trunks and roots, and they may continue to develop after timber has been processed, there are records of adult longhorns emerging from furniture and structural timber after remaining dormant for two decades. Some species are pests in forest plantations, orchards and among nursery stock, they generally attack damaged or weakened plants and then greatly accelerate the damage, and a large number of species develop in dead wood, fallen timber, decaying logs, fence-posts etc. and they are important decomposers in forest ecosystems. Adult longhorns are generally short-lived and have a brief season, in temperate regions from late spring to early summer, most fly well and may be observed around flowers in wooded areas, some are slow-moving and tend to remain around the host material while others can move very quickly and disperse long distances, they these can often be observed feeding upon bark, foliage, flower parts and pollen etc. Some are flightless and have the elytra fused, these are generally terrestrial, live on grasses or herbaceous plants and disperse only short distances, the populations are prone to fragmentation and so they tend to be speciose e.g. the Palaearctic genus Dorcadion (Dalman, 1817). Most species take between one and three years to complete the life-cycle although in warmer climates this may be complete in two or three months. The life history of many species is typical; the females oviposit in damaged wood, bark-crevices or in the soil around the roots, in fallen timber or in herbaceous stems etc. and the larvae emerge after a week or two and immediately begin to feed upon the host material, either among the softer cambium or by boring into stems, some bore directly into roots or into the soft xylem of decaying logs etc., as they grow they bore deeper into the wood producing often characteristic tunnels, or up and down herbaceous stems, but in general they remain near the surface. Pupation occurs within the host or in an earthen cell among the roots, and adults eclose either in the autumn and remain in place until the following season or in the spring and emerge directly. Among those emerging in the autumn are species of Cerambyx (Linnaeus, 1758), Molorchus (Fabricius, 1792), Pogonocherus (Dejean, 1821), Acanthocinus (Dejean, 1821), Mesosa (Latreille, 1829) and Phytoecia cylindrica (Linnaeus, 1758).

The Western Palaearctic Fauna, with Special Reference to the UK

This will be no more than a brief look at the European fauna as much more detail will be given in the various pages. The European longhorn fauna includes about 700 species in about 6 subfamilies; the higher-order classification will be found to vary as some subfamilies will be listed as tribes e.g. the Necydylinae (Latreille, 1825) is often listed as a tribe of the Lepturinae (Latreille, 1802). Diversity is greatest in warmer regions and decreases from south to north along a temperature gradient. Turkey has about 600 species but is in some sense ‘well-placed’ between Asia, The Middle-East and Europe, while Italy has about 275, Croatia 220, Germany 195, France 250, Denmark about 75, Scandinavia more than a hundred and the U.K. about 70. These figures include the native or established species but all European countries have extensive lists of occasionally recorded species, both from surrounding countries and from those imported with timber etc. from farther afield; about 70 of these ‘occasional’ have been recorded in the U.K. or about the same number as the established species. These figures are in line with saproxylic groups generally where diversity is always greatest at southern and middle latitudes. Most northern European species, certainly those from the U.K. form parts of much wider European or Eurasian distributions and a few e.g. Rhagium inquisitor (Linnaeus, 1758), Callidium violaceum (Linnaeus, 1758) and Judolia sexmaculata (Linnaeus, 1758) are Holarctic.

As with many other saproxylic groups many xylophagous longhorns are in decline and have been for some decades, mostly due to the destruction of forested areas or their commercial management, and this continues today. Only two species are protected by law, Rosalia alpina (Linnaeus, 1758) and Cerambyx cerdo (Linnaeus, 1758), neither of which occur in the U.K. Economic loss due to pest species is not so serious as in some other parts of the world but nonetheless a few species are noteworthy; Hylotrupes bajulus (Linnaeus, 1758), the House Longhorn, causes occasional and sometimes severe damage to property but this has declined over recent decades as new constructions materials are less prone to attack, species of Monochamus (Dejean, 1821) and Tetropium (Kirby, 1837) can cause serious damage in conifer plantations, and amenity trees and shrubs are attacked by a wide range of genera including Cerambyx (Linnaeus,1758), Callidium (Fabricius, 1775), Arhopalus (Audinet-Serville, 1834) and Asemum (Eschscholtz, 1830) but again such species are in general decline due to ‘improvements’ in environmental management e.g. the removal of fallen timber and damaged trees. A much greater threat is posed by invasive foreigners; in recent years two species in particular pose a serious threat, Anoplophora glabripennis (Motschulsky, 1853), the Asian Longhorn, and A. chinensis (Forster, 1771), the Citrus longhorn, both native to China and polyphagous on various hardwoods, have become established throughout Europe, at the moment (2017) only in scattered local populations but they are extremely invasive and damaging, and they have caused serious damage in various Nearctic regions. Another destructive invasive, Callidiellum villosulum (Fairmaire, 1900), the Brown Fur Longhorn which is another Chinese native, has recently been recorded established on Malta. Between 1990 and 2010 nineteen foreign species have become established in Europe and if this is a consequence of changing climate then perhaps we can look forward to many more.

With the exception of a few iconic species such as Rosalia and Cerambyx the U.K. fauna, while only ten percent that of Europe, is a fair representation of the wider fauna. Many species are common along the northern coasts of Europe e.g. Spondylis buprestoides (Linnaeus, 1758), an invasive and sometimes destructive species, and it is baffling why they have not become established here, and some that hold only a tenuous place on our U.K. list e.g. Dinoptera collaris (Linnaeus, 1758) are common and often abundant on the continent. On the other hand the widespread European Stictoleptura cordigera (Fussli, 1775) has recently become established in the south of England and so our fauna may be undergoing some modern changes. The destruction of woodland habitats across Europe since the twentieth century occurred much more thoroughly hundreds of years previous in the U.K. and ever since our countryside management has been appalling and so it is perhaps no wonder that our cerambycid fauna has become impoverished; many of those on our list are rare and local. One genus that occurs throughout central and southern Europe but is notably absent from the U.K. is Dorcadion (Dalman, 1817) - a very speciose group of terrestrial and flightless longhorns, they are associated with herbaceous plants and some have been pests of cereal crops, they live in colonies in open situations which become easily separated and local populations develop in isolation leading to rapid differentiation and speciation, in Russia there are more than 150 species occurring in steppe habitats and so it might be imagined that parts of the U.K. would form ideal habitats. Some formerly common and widespread species have declined drastically over recent decades due to habitat loss and modification e.g. D. fulginator (Linnaeus, 1758) is now generally endangered and extinct in some areas e.g. Luxembourg.

The majority of European longhorns are saproxylic; in Germany about 50% of species develop in softwood while about 26 develop in hardwoods, other species develop in a range of herbaceous plants although only two such species occur in the U.K., Phytoecia cylindrica (Linnaeus, 1758) and Agapanthia villosoviridescens (DeGeer, 1775), in each case members of much larger European genera. Most are active during May and June although some are later e.g. Prionus coriarius (Linnaeus, 1758), while others may occur earlier depending upon the season e.g. Clytus arietis (Linnaeus, 1758) and Acanthocinus aedilis (Linnaeus, 1758). A few occur year round and may be active during mild spells through the winter e.g. species of Pogonocherus (Dejean, 1821). They may be collected by searching bark and logs etc. or flowers and sap in wooded areas, some have characteristic flight behaviour e.g. Pachytodes cerambyciformis (Schrank, 1781) hovers above flowers like a bee while Clytus darts quickly between flowers like a wasp. Keeping an eye along woodland margins or around solitary trees near wooded areas may reveal specimens in flight e.g. Leptura aurulenta (Fabricius, 1792) or species of Tetropium (Kirby, 1837). Some crepuscular species e.g. Prionus, Arhopalus (Audinet-Serville, 1834) and Asemum (Eschscholtz, 1830) may be seen in flight as the light fades, and many of these are attracted to light e.g. this is the easiest way to find Phymatodes testaceus (Linnaeus, 1758). Both phytophagous and saproxylic species are generally associated with a wide range of hosts, although our U.K. phytophages generally occur on umbels, and many genera occur on either hardwoods or softwoods but a few species within widely polyphagous genera may show a very restricted host range or even monophagy e.g. in the U.K. Semanotus russicus (Fabricius, 1776) is partial to hedging conifers, while Oberea oculata (Linnaeus, 1758) develop in species of Salix. On the other hand species of Monochamus (Dejean, 1821), a Holarctic and African genus of more than 160 species, mostly attack conifers. Some may choose an unlikely range of hosts e.g. Pogonocherus hispidus (Linnaeus, 1758) usually develops in ivy but has also been recorded from Cornus (Dogwood), Corylus (Hazel), Ilex (Holly) and Euonymus (European spindle). In general the Cerambycinae and Lamiinae choose hardwoods while Spondylidinae choose conifers. Some groups choose both types of wood e.g. Rhagium (Fabricius, 1775) and Oxymirus (Mulsant, 1863). Timber in all stages of decay may host cerambycids, even healthy trees although they will seek out damaged areas of bark, generally low down on the trunk or among the roots, and fallen timber and logs in an advanced stage of decay will often be found to host them. It is the larvae that damage the wood as many species take two or three years to develop, tunnelling through the outer layers of xylem and going deeper as the surface is obliterated. Adults do feed but their effects are minimal; Lepturinae generally feed on flowers when they assemble to mate although some species e.g. Stenocorus meridianus (Linnaeus, 1758) and Stictoleptura rubra (Linnaeus, 1758) only occasionally visit flowers. Many Lamiinae as well as Cerambycinae visit flowers to feed and in particular may be found on umbels and blossom, among the more common of such species are Clytus arietis, species of Tetrops (Stephens, 1829) and Phytoecia (Dejean, 1835). Most Lamiinae are bark and stem feeders; adults of Acanthocinus aedilis and Saperda populnea (Linnaeus, 1758) etc. may be observed chewing into bark, often prior to oviposition, while Cerambyx species will feed upon sap as well as fallen fruit. Foliage feeders include Lamia textor, and species of Leiopus (Audinet-Serville, 1835) and Phytoecia (Dejean, 1835). Some species of Leiopus as well as Stictoleptura rubra have been observed feeding upon fungi fruiting among bark crevices.

Description

Although very variable longhorns are generally recognizable as the elongate and cylindrical or flattened form is distinctive, certain Tenebrionoidea groups include superficially similar species but here the form of the tarsi and the tarsal formula are different. The basic form of the Lamiinae, Cerambycidae and Lepturinae will soon become familiar. Most species are finely pubescent but this often matches the colour of the underlying cuticle and so it is often not obvious. The head is always visible from above; in some groups it is partially recessed into the prothorax so that the temples are not, or only narrowly, visible e.g. Prioninae and Lamiinae, while in others, typified by the Lepturinae, it is freely articulated beyond the anterior pronotal margin. Among the European fauna the Lamiinae are distinctive with the head vertically inclined (hypognathous), in the Lepturinae it lies about in line with the plane of the body (orthognathous) while in the Cerambycinae it is oblique, these orientations soon become familiar and most species can be placed in the field. The eyes are well-developed, especially in nocturnal species where they are larger and more coarsely faceted, they usually follow the contour of the head or are only weakly convex and they are most prominent from above in Lepturinae. The shape varies from oval to reniform or narrow and curved around the antennal insertions; in extreme cases e.g. Tetropium, they may be completely divided. The mandibles are robust and heavily sclerotized, generally broad and triangular in form, sharp internally and often bifurcate apically. The maxillary palpi are four-segmented with the terminal segment varying from securiform to cylindrical and truncate; the labial palpi are three-segmented and generally at least to some extent expanded to securiform. The vertex and frons are flat to weakly concave or convex and there is often a median longitudinal furrow or carinae between the eyes, the clypeus is well-sclerotized and separated from the frons by a distinct suture and the labrum is freely articulated and generally covered by the clypeus; it is often only visible by the fringe of long setae lying along the anterior margin. The antennae are in some sense the defining character of the group, they are typically long or very long and thin, often reaching to the elytral apex or beyond although in some groups they are short and rather broad e.g. Clytus, and in Spondylis they are more-or-less moniliform. In most groups they are 11-segmented although in the male of Prionus and in species of Agapanthia they have twelve. The basal segment is long, broad and often curved or expanded towards the apex, and sometimes elongate-pyriform, the second is short and quadrate to transverse, often globular and sometimes simply cylindrical, the remainder; 3-11 are usually elongate, sometimes extremely so, and cylindrical or expanded towards the apex but the morphology varies widely from strongly serrate in Prionus to very elongate in Acanthocinus, in most species they are pubescent from the second or third segment and in some tropical species they have elaborate arrangements of setae towards the apex of various segments, a condition approached in Rosalia. The pronotum varies from simply cylindrical or barrel-shaped to campanulate with produced posterior angles, in many it is flattened dorsally and there may be surface structure as e.g. in Hylotrupes. With the exception of the Prioninae the lateral margins are not bordered but there may be tubercles, spines or small teeth. The surface is usually punctured, often strongly so, and microsculptured. The prosternum is transverse and deep with a distinct and very variable process that extends beyond the coxae which are round to transverse-oval in shape; the prosternal epimera and episterna vary in shape but are generally proportionally small. The mesosternum is small, variable and produced posteriorly into a rounded or truncate process which is often incised to receive the produced anterior margin of the metasternum. In most groups the elytra cover the abdomen but there are many exceptions e.g. Necydalinae (Latreille, 1825), Molorchus (Fabricius, 1792) or Glaphyra (Newman, 1840), they are either broadest at the shoulders and narrow towards the apex, or are parallel or nearly so, only rarely do the broaden posterior to the middle e.g. in Stenostola (Dejean, 1835). The apex may be rounded, oblique or truncate and in some groups e.g. Pogonocherus (Dejean, 1821) it has teeth or spines at the angles. They vary from cylindrical to flattened; the surface is randomly punctured and usually smooth i.e. without distinct striae although in Spondylis there are longitudinal ridges. In most species the hind wings are well-developed and flight is strong. In most species the legs are long and slender although in many Spondylidinae and Lamiinae they are short and robust. The coxae project above the surrounding cuticle and vary from conical or globular to transverse-cylindrical with the meta-coxae reaching the elytral epipleura, and the cavities may be open or closed posteriorly. The femora are generally long and sub-parallel or distinctly thickened beyond the middle and in many cases strongly clavate. The tibiae are usually simple, although variously grooved in Lamiinae, and straight with two small spurs on the inner apical angle, in some Spondylidinae they are toothed along the external margin. The tarsi are 5 segmented although the fourth segment is often small or rudimentary or hidden within the bilobed third segment; this Chrysomelid arrangement of simple basal segments and a deeply bilobed third is a good guide to the group when compared to superficially similar Tenebrionoid families. In many species the basal segment, especially on the meta-tarsi is very long compared to the others. Sexual dimorphism is common among the family and often manifest in general habitus, antennal length, body proportions, and many females have a prominent and heavily sclerotized ovipositor.

Most Cerambycid larvae are pale and soft-bodied, never darkened or heavily-sclerotized, they are elongate and usually cylindrical or nearly so but flattened forms do occur, the mandibles are short and robust, generally triangular or curved, the legs short or much reduced, and abdominal ampullae are always present although sometimes very small, and they lack segmented urogomphi. Many larvae develop over several years and grow disproportionally large compared with their adult forms.