THANEROCLERIDAE Chapin, 1924 

False Chequered Beetles

The single British species, Thaneroclerus buquet, has been only very rarely recorded in the UK as a pest of stored food products.

POLYPHAGA Emery, 1886

CLEROIDEA Latreille, 1802

THANEROCLERUS Lefebvre, 1838 

T. buquet (Lefebvre, 1835) 

4.5-6.5mm

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Introduction

Closely related to the Cleridae, and often still to be found in the literature as a subfamily of that group, but differing most obviously in the narrow middle and hind tarsi which lack bilobed segments, the long claw segment, mandibles with a deep basal notch, abdominal sternites ventrally bordered and the genitalia; the tegmen lacks a phallobasic apodeme.  The family includes very few species but is cosmopolitan in distribution; two tribes are recognized of which one, Zenodosini Kolibá, 1992 includes the single Nearctic species Zenodosus sanguineus (Say, 1835), a predatory saproxylic beetle widespread in the USA and Canada. Thaneroclerini Chapin, 1924 includes at least 6 genera in 3 subtribes; about 6 species occur in Australasia and about 10 are Palaearctic although only Thaneroclerus buquet (Lefebvre, 1835) extends to Europe, 2 species occur in Central America and at least one, Isoclerus triimpressus (Pic, 1936) has been introduced and is now established in Brazil.  Most species are known from only a very few specimens and are of very limited distribution e.g. of the Palaearctic species there are Indian and Japanese endemics.

Description

The species are small, 2.5-8mm and often distinctively coloured or patterned and will generally be recognized as clerids but differ as outlined above; Zenodosini differs from the Thaneroclerini in having the front coxal cavities transverse and open behind, a normally developed ninth abdominal segment and 5-segmented tarsi, although in the latter tribe there are species with 4-segmented and 5-segmented tarsi. From our UK point of view the only species of interest is the cosmopolitan Thaneroclerus buquet. Thaneroclerus Lefebvre, 1838 includes 5 further species, all from the Old World; T. impressus Pic, 1926 from North Vietnam, and T. aino (Lewis, 1892), T. dermestoides (Klug, 1842), T. tabacci (Matsumura, 1935) and T. quasitardatus (Corporaal, 1939) from Asia.  Within the family Thaneroclerus is distinguished by the following characters. Entire dorsal surface with fine pale pubescence. Head transverse and convex with longitudinal wrinkles, emarginate frons and coarsely-faceted and rather flat eyes. Antennae 11-segmented with a loose, three-segmented club. Terminal maxillary palpomere cylindrical and tapering, terminal  labial  palpomere  broadly  triangular.  Gular  sutures  parallel  and

long. Pronotum variously narrowed anteriorly and posteriorly, bordered laterally and with 3 variably deep and wide depressions. Prosternum process dilated apically behind round and closed coxal cavities. Front and middle coxae spherical. Middle coxal cavities closed by the meso- and metasternum. Wings variously developed, with a radial cell but lacking an anal cell. Elytra elongate and parallel-sided or slightly dilated towards the apex, impressed adjacent to the suture and randomly and quite finely punctured, continuously rounded apically and completely covering the abdomen. Legs short and robust, tarsi 5-segmented; basal front tarsal segments bilobed, tarsi otherwise without lobed segments, claw segment long and dilated apically, claws smooth and without basal teeth.

Thaneroclerus buquet (Lefebvre, 1835)

Originally native to India this species is now cosmopolitan having been spread with the international trade in foodstuffs etc. it was first reported from the New World during the 1920’s and now occurs sporadically throughout that region including many Caribbean Islands, and further afield it is regularly reported from Europe, Asia, Africa and Australasia etc. Outside of tropical and warmer regions it is unlikely to become established but generally persists in areas where large volumes of produce are handled or stored. Both adults and larvae are predators of other insects among a very wide range of stored products e.g. coffee and cocoa beans, tobacco, spices and herbs, nuts, flour, tubers, dried fruit and a range of cereals and grains. The the range of prey species is also very wide and includes beetles from a range of families including Anthribidae Billberg, 1820 (Araecerus fasciculatus DeGeer, 1775, the coffee-bean weevil), Ptinidae Latreille, 1802 (Lasioderma serricorne (Fabricius, 1792), the tobacco beetle), Tenebrionidae Latreille, 1802 (Tribolium ferrugineum (Fabricius, 1781), a flour beetle, and Curculionidae (Sitophilus oryzae (Linnaeus, 1763), the rice weevil) etc. and because these species are all cosmopolitan pests of stored products, T. buquet may occur worldwide wherever these pests are established; typically they occur in warehouses and grain storage facilities. In the UK it is recorded only occasionally as an accidentally imported and transient species, on one occasion among imported root ginger, and it is only doubtfully included on the British list of species.

Adults are very distinctive due to the elongate form, clubbed antennae and the form of the pronotum. 4.5-6.5mm. Entirely dark brown or reddish-brown with fine pale pubescence. Head and pronotum densely and quite finely punctured; the punctures slightly elongate, elytra less densely but slightly more strongly punctured. Pronotum almost parallel-sided in the anterior half then roundly tapering to a sub-basal constriction, lateral and basal margins finely bordered, surface with a variable median longitudinal impression and several generally ill-defined lateral impressions. Elytra elongate, about 1.8:1, and slightly widened towards the apex, randomly punctured and with a longitudinal impression extending from near the base to at least the middle where the suture is variously but usually conspicuously raised.

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