OEDEMERIDAE Latreille, 1810

False Oil Beetles

A characteristic group, active on flowers or nocturnally. Species such as the thick-legged flower beetle (O. nobilis) will quickly become familiar, while others are very local and rare. 

POLYPHAGA Emery, 1886 

TENEBRIONOIDEA Latreille, 1802

4

4

10

5-13mm

Suborder:   

Superfamily:

Tribes:

Genera:  

Species:  

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Around the World

The Oedemeridae is a cosmopolitan family of about 1500 described species in 80 genera and 3 subfamilies. The vast majority of the species are included within the Oedemerinae Latreille, 1810 and are of a characteristic general appearance which will soon be recognized by anybody familiar with the fauna of a particular area e.g. even the U.K. fauna will give a good idea of the overall form of the group. The other two subfamilies are much smaller and of more limited distribution. The Polypriinae was only recently added to the group by Lawrence in 2005 and includes 2 genera, all species lack elytral costae and the claws have a strong basal tooth, they differ fundamentally from other Oedemerids in genitalia structure. The monotypic Dasytomima Lawrence, 2005 includes D. rachelae Lawrence, 2005 a rather atypical, although recognizably Oedemerid, mottled brown species with a sculptured pronotum and elytra, long erect pale setae among the fine and dense recumbent pubescence across the dorsal surface and, unique among the family, interfacetal setae. The species occurs on grassland in Tasmania and southern Queensland. The genus Polypria Chevrolat, 1874 includes 3 New World species; P. cruxrufa Chevrolat, 1874, the Red-cross Oedemerid, so named after the elytral markings, occurs in the southern U.S.A. and Central America while P. lateralis Pic, 1902 and P. brevipennis Pic, 1902 occur in Brazil. The placement of this genus remains uncertain and it has variously been included within the Salpingidae, Mycteridae and Melandryidae. Calopidinae Costa, 1852 includes a single tribe, Calopodini Costa, 1852 and two genera. They are distinguished by the antenna being placed upon a tubercle within the deep emargination of the eye and the mesocoxae being separated by a posterior process of the mesosternum. Calopus Fabricius, 1775 includes two species; C. angustus LeConte, 1851 is Nearctic while C. serraticornis (Linnaeus, 1758) occurs throughout central, northern and Eastern Europe extending to the Caucasus and Siberia. They are drab brown or testaceous insects distinguished within the tribe by their bifid mandibles, elytral costae and large size, >15.5mm. They inhabit wooded areas and develop in a range of conifer species, the adults are nocturnal and attracted to light. Sparedrus Dejean, 1821 is a large genus of about 40 species distributed throughout the Holarctic, Oriental and Neotropical zones, t he greatest  diversity is in Asia and  only two species  occur in the 

United States, both of which are rare. Most species have a restricted distribution and many occur in the India, Pakistan and Nepal regions. Three species occur in Europe; S. testaceus Hope, 1797 is widespread although local and rare from northern Italy east through the Balkans to Greece, S. orsinii Costa, 1852 is endemic to Italy and Sicily, and S. lencinae Vázquez, 1988 occurs in a few mountain localities in south-eastern Spain. The species occur in woodland where they develop in a range of hard and soft woods, adults are mostly nocturnal and are attracted to light. They are generally smaller than Calopus, lack elytral costae and have the mandibles entire at the apex. No members of the subfamily have been recorded in the U.K.

Genera of the Oedemeridae Latreille, 1810 have been variously classified into two subfamilies; Nacerdinae Mulsant, 1858 which includes two tribes, the Ditylini Mulsant, 1858 and the Nacerdini Mulsant, 1858, and the Oedemerinae which includes the Stenostomini Mulsant, 1858, Asclerini Gistel, 1856 and the Oedemerini Latreille, 1810. However, the limits of the various genera have yet to be resolved fully and another system, which places all the genera within tribes of the Oedemerinae, is also in use; the Ditylini includes the Holarctic Ditylus Fischer von Waldheim, 1817, the Australian Agasma Newman, 1850, the (mostly)old world genera Diplectrus Kirsch, 1866, Ascleranoncodes Pic, 1915 and Chrysanthia Schmidt, 1844, and the new world genera Diasclera Reitter, 1913, Heliocis Arnett, 1951, Eumecomera Arnett, 1951 (sometimes included in Asclerini) and Sisenes Champion, 1889. The Nacerdini Mulsant, 1858 includes three old world genera, all of which are represented in Europe; Nacerdes Dejean, 1834, Opismea Reitter, 1880 and Agoncodes Dejean, 1834. Stenostomatini Mulsant, 1858 includes three species of Stenostoma Latreille, 1810 which occur in the Mediterranean area. Oedemerini Latreille, 1810 includes two genera represented in the western Palaearctic; Oedemera Olivier, 1789 and Oncomera Stephens, 1829 (sometimes a subgenus of Oedemera) and the Asian and Oriental Dryopomera Fairmaire, 1897. The remaining genera are included in the Asclerini Semenov, 1894.

The only truly cosmopolitan genus is Nacerdes Dejean, 1833; as well as being represented by many species across the Holarctic region, Southeast Asia and Africa, one species; N. melanura (Linnaeus, 1758) has been transported worldwide by human activity. Most areas are relatively rich in genera, and many genera, while widespread, are restricted to particular zones e.g. Bawlipalpus Brown, 1880 and Thelyphassa Pascoe, 1876 from New Zealand, the exclusively African Asclerosibutia Pic, 1914, Ditylomorphila Ŝvihla, 1985, Diltylomorphus Ŝvihla, 1986, and Zabriola Fairmaire, 1901 which contains four species including a Madagascan endemic, and the Southeast Asian Ascleranoncodes Pic, 1915, Falsonadanus Pic, 1943, and Pseudonerdanus Pic, 1923. More widespread genera include the pantropical Copodita Leconte, 1866 and the Holarctic Ditylus Fischer von Waldheim, 1817. New world genera include Hypasclera Kirsch, 1866, Oxacis Leconte, 1866, Rhinoplatia Horn, 1868 and Vasaces  Champion, 1889. Alloxacis Horn, 1868 includes several Neotropical species as well as endemics in Jamaica and The Galapagos. Chrysanthia W. Schmidt, 1844, Ischnomera Stephens, 1832 and Oedemera Olivier, 1789 are widespread Palaearctic genera while several Asian genera extend into Southeast Asia and Australia e.g. Ascleropsis Seidlitz, 1899, Diplectrus Kirsch, 1866, Dryopomera Fairmaire, 1897 and Indasclera  Ŝvihla, 1980, and the large genus Probosca W. Schmidt, 1846 occurs in Asia as well as Africa. Many genera are of much more limited occurrence e.g. Chitona W. Schmidt, 1844 is represented by about ten species in Mediterranean North Africa, as is Alloxantha Seidlitz, 1899 with plenty of endemics; three from Iran, Four from the Canary Islands and one each from Algeria and Saudi Arabia. Monosigynes Vasquez, 2004 contains four species from Equatorial Guinea. The family is also rich in monotypic endemic genera e.g. Colobostomoides  Ŝvihla, 1983 from Iran, Dainsclera  Ŝvihla, 1997 from China, Diplectroides Champion, 1889 from Colombia, Heliocis Arnett, 1951 from the U.S.A., Hypascleroides Ŝvihla, 1986 from Yemen, Hyperoselaphus Mizota, 1999 from Japan and Southeast Asia, Idgiomimula Blaire, 1926 from Tanzania, Melanonthia Blair, 1926 from South Africa, Nacerdochroides  Ŝvihla, 1986 from Indonesia, Paraessinia Ŝvihla, 1986 from several Indian Ocean islands, Pterosessinia Ŝvihla, 1986 from Namibia and Pythoplesius Kolbe, 1903 from Patagonia. A very interesting genus, from a biogeographical point of view, is Sessinia Pascoe, 1863 with about fifteen species variously distributed in New Zealand, Madagascar, New Guinea, Ethiopia and the Philippines.                                        

Description

2.5-26mm although the majority are between 7 and 18mm. Elongate species with a characteristic appearance; 2.5-4.5X as long as wide, parallel sided or nearly so, and flattened , dorsal surface smooth or only moderately sculptured, generally pubescent to some extent, usually very finely so. Often metallic green, bronze or blue but many are uniformly testaceous to black; some are bicoloured, mottled or strikingly maculate. Head prognathous, sometimes strongly produced, often with distinct temples but generally not abruptly constricted to the base. Eyes flat to strongly convex and often emarginate anteriorly. Antennae usually filiform with most segments elongate; the second tends to be small in most groups and in some the middle segments are expanded e.g. Pseudolycus ater Pic, 1931 segments 3-7 are enlarged while in Dohrina miranda Newman the male has segments 5-8 expanded, mostly 11-segmented; 12-segmented in Nacerdes, and sometimes the terminal segment is constricted so giving the appearance of being 12 segmented, inserted in a pit or on a tubercle, or both, in front of the eyes or within the emargination, antennal grooves absent. Frontoclypeal suture usually absent, head often produced and rostrum-like anterior to the eyes, a feature which, combined with the narrow pronotum and broad shoulders, gives a distinctive appearance to most members of the family, anterior margin of the clypeus truncate or weakly curved, labrum free; transverse to elongate, sometimes expanded towards the apex, truncate to emarginate. Mandibles robust; transverse to elongate, with one or two apical teeth and often with an internal subapical mola. Apical segment of the maxillary palpi cylindrical and often truncate to cultriform, securiform or fusiform. Mentum usually strongly transverse. Pronotum slightly transverse to distinctly elongate; generally widest in the anterior half and narrowed towards the base, anterior angles usually rounded, sometimes distinctly angled but never produced. Anterior and posterior margins bordered, often strongly so, lateral margins almost always absent. Dorsal surface variously sculptured; often with a transverse depression and a lateral constriction, and often deeply depressed in front of the posterior margin, the cuticle often, or usually, rugose and punctured. Prosternum wide and flat or weakly convex anterior to the coxae, coxal cavities transverse to round and touching or nearly so, externally open and sometimes with narrow lateral extensions, the process very narrow and not extending far, if at all, posterior to the coxae, often incomplete. Procoxae convex and extending below the level of the prosternum. Scutellum flat; usually elongate and triangular or sometimes rounded or truncate apically. Elytra elongate; 3-6X longer than the pronotum, parallel to weakly dilated apically or separately narrowed so that the wings and parts of the abdomen are exposed, apices entirely or separately rounded. Each elytron generally with 3 or 4 (including the sutural) longitudinal costae, the outer sometimes joining the lateral margin in the anterior half, without a scutellary stria, surface generally rugose and randomly punctured. Epipleura generally incomplete; often very narrow or missing posterior to the basal third. Mesocoxae conical and projecting below the mesosternum, the cavities circular to slightly transverse, oblique or strongly oblique, almost always contiguous, the mesoventral process usually incomplete or sharply pointed. Metacoxae transverse, horizontal or oblique, extending laterally to the elytra, contiguous or very narrowly separated. Hind wings usually well-developed and most species are strong fliers. Abdomen with 5 or 6 ventrites; 1 and 2 connate and similar in length, the fifth sometimes emarginate in males, the eighth often deeply emarginate or lobed. Legs long and slender, the junction of the femora and trocanters strongly oblique so that the femora are sometimes in contact with the coxae.  Hind femur sometimes dimorphic, being strongly dilated in males. Tibiae long and parallel although the hind tibiae are sometimes modified in the males of some species; angled externally or produced apically, each with a pair of small apical spurs on the inner apical angle, in Nacerdes the pro-tibiae have only a single spur. Tarsi 5-5-4 with the penultimate segment bilobed and the basal segments often triangular. The penultimate segment, and various others in different species, have a dense covering of adhesive setae ventrally. Claws well-developed, weakly curved and sharp, sometimes expanded or toothed at the base.  The general form of the subfamily will be appreciated from a consideration of the British species.

Ecology

The name of false blister beetles refers to the fact that some species produce cantharidin or similar substances, the same toxins found in the true blister beetles, Meloidae, the susceptibility of humans to blistering varies enormously and most people seem to be unaffected by oedemerids generally but in some areas they are notorious; in Japan they are called poisonous beetles, and in the south-eastern U.S.A., especially around the Florida Keys, the species Oxycopis mcdonaldi (Arnett, 1951) is a nuisance in tourist resorts, they are nocturnal and attracted to light and sometimes occur in large numbers around swimming pools and restaurants etc., and cause blistering and burn-like effects when squashed against the skin. No such problems occur in the U.K. On a more commercial scale the only pest species is Nacerdes melanura (Linnaeus, 1758), the wharf borer. Adults are either crepuscular or nocturnal, in which case they tend to be drab and are attracted to lights, or, as in many metallic species, diurnal and active in sunshine. The biology of only a few species is known, and the detailed knowledge of Nacerdes is the result of its pest status. Adults visit flowers, often in numbers, to feed on pollen prior to mating; some species are monophagous or oligophagous but most feed upon a range of plants and the scent acts as a congregating attractant. Maturation feeding is generally brief but females will not mate until they have fed. After feeding the pollen grains are stored in an intestinal sac where, under enzymic degradation, they germinate and begin to grow, at this stage they are digested and the products are used in oogenesis. Many species, if not most, are saproxylic and lay eggs under bark or among decaying wood, but many use herbaceous plants as hosts, the larvae developing in the stems. After emerging the larvae of many saproxylic species drop to the ground and burrow into the soil to complete their life-cycle feeding on roots. Those developing in herbaceous plants tend to pupate in the stems. Soil dwelling larvae feed externally on roots or within rhizomes etc and pupation occurs in a subterranean cell near the host. Some larvae construct vertical burrows where they live and feed on roots. There is almost always a single generation each year and in temperate zones pupation in the autumn follows summer larval development, adults may eclose in the autumn and pass the winter in a cell before emerging in the spring or they may eclose and emerge in the spring. In many cases the adults will emerge to coincide with the flowering of certain plants.

UK Species

Chrysanthia nigricornis

Oedemera femoralis

Ischnomera caerulea

Oedemera lurida

Ischnomera cinerascens

Ischnomera cyanea

Oedemera virescens

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