LAEMOPHLOEIDAE Ganglbauer, 1899

Flat Beetles

These small, flat beetles are occasionally encountered on dead wood and under bark, both at night and during the day. A number of species occur in stored products.

POLYPHAGA Emery, 1886 

CUCUJOIDEA Latreille, 1802

3

9

1.3-5mm

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Around the World

This is a cosmopolitan family of about 450 species included in 40 genera but at present there is no higher order classification above the level of the genus, it was formerly included in the family Cucujidae Latreille, 1802 and almost all of the species were included in the genus Laemophloeus Dejean, 1835 but defining the limits of this genus has hampered more recent revisionary work on the family but as currently defined it includes 28 species; 6 Palaearctic, 9 Nearctic and 16 Neotropical. The greatest diversity is in tropical regions although temperate species will give a good idea of the family as a whole; 58 species occur in the Nearctic region and 20 or so in Europe. The distribution of the family is interesting; species range from cosmopolitan, some of which are pests, to island endemics. The genus Cucujinus Arrow, 1920 includes two subgenera; Cucujinus s.str. includes 3 African species while Paracucujinus Lefkovitch, 1962 includes 2 species from Madagascar, one of which, C. coquereli Grouvelle, 1899, is endemic to Reunion Island. Nipponophloeus Sasaji, 1983 includes one species restricted to Japan and one distributed through Japan and Russia. Caulonomus Wollaston, 1862 includes the single species C. rhizophagoides Wollaston, 1862 which is endemic to The Canary Islands. Heterojinus Sen Gupta & Mukhopadhyay, 1978 includes the single Indian species H. semilaetanus (Grouvelle, 1913), and the only species of Rhinolaemus Steel, 1954, R. maculatus Steel, 1954, known from only a single specimen, is endemic to Fiji. Brontolaemus Sharp, 1885 includes four species endemic to Hawaii. In some cases the distribution is very uncertain e.g. the single species of Blubos Lefkavitch, 1962, B. matris Lefkavitch, 1962 is known from one specimen collected in the Congo more than 60 years ago. Some genera have a wide distribution e.g. Cryptolestes Ganglbauer, 1899 includes about 50 species and is cosmopolitan, Laemophloeus Dejean, 1835 with about 30 species is Holarctic and Neotropical, Leptophloeus Casey, 1916 with 27 species is cosmopolitan and Parandrita LeConte & Horn, 1880 is Nearctic and Neotropical and includes one  species from  Hawaii. Several  genera occur  throughout the 

New World e.g. Charaphloeus Casey, 1916 with 20 species, Deinophloeus Sharp, 1899 with 5 species and Rhabdophloeus Sharp, 1899 with 5 species, while some are confined to the Neotropics e.g. Odontophloeus Thomas, 1984 with 4 species or Phloeipsius Casey, 1916 with a single species. Genera occurring only in Africa include Gannes Lefkovitch, 1962 with 2 species, and the four species of Mariolaemus Lefkovitch, 1962. The 5 species of Passandrophloeus Kessel, 1921 occur in Africa and Asia while the 9 species of Lathropus Erichson, 1845 are wholly Palaearctic.

Ecology

Most of the species are saproxylic both as adults and larvae, occurring under the bark of both deciduous and coniferous trees, and are thought to be fungivores although some occur in the galleries of other bark beetles and are predaceous. Some are synanthropic and have been pests of a very wide range of stored food products, especially cereals, grains and dried fruit; among the most serious of these belong to the genus Cryptolestes Ganglbauer, 1899, more especially C. ferrugineus (Stephens, 1831), C. pusilloides (Steel & Howe, 1952), C. pusillus (Schönherr, 1817) and C. turcicus (Grouvelle, 1876) all of which are cosmopolitan.

Description

Most of the species are tiny, 1-3mm but some tropical species can reach 5mm and, despite the wide morphological variation, they soon become recognizable due to the characteristic broad head and pronotum and the usually obvious raised lines on the forebody and often the elytra. Shape very variable, most species are oval to elongate and very flat although e.g. the African Mestolaemus longicornis Lefkovitch, 1962 is unusual in having short and almost round elytra, and a few genera e.g. Leptophloeus Casey, 1916 or Dysmerus Casey, 1884 are long and almost cylindrical being adapted to living in galleries rather than under bark. Most are drab brown to black although there are many colourful, or at least maculate, species e.g. the Palaearctic Laemophloeus monilis (Fabricius, 1787), the Nearctic L. fasciatus Melsheimer, 1884 or species of the Nearctic genus Rhinophloeus Sharp, 1899. The head is generally comparatively large and transverse although in the Nearctic and African Nartheticus LeConte, 1861 it is very elongate and in Rhinolaemus maculatus Steel, 1954 from Fiji the head is produced in front of the eyes. The mandibles are large, robust and often produced anteriorly, sometimes e.g. in Rhinolaemus Steel, 1954 very strongly so, with 2 or more variously developed apical teeth and sometimes a sub-apical tooth. The maxillary palps are 4-segmented and the labial palps are 3-segmented and in each case the terminal segment is the longest. Eyes very variable, usually convex and protruding, in Odontophloeus Thomas, 1984 species very well defined, and in some species e.g. members of the widespread genus Narthecius LeConte, 1861, flattened, in many species they are asymmetric and have large facets. There is at least one lateral carina beside the eyes – typical of the family – and the frons is often expanded, sometimes very widely so, for example Dysmerus basalis Casey, 1884. A frontoclypeal suture is sometimes present, for example in species of Placonotus Macleay, 1871, and the labrum is large; the anterior margin rounded to truncate or strongly emarginate, some species have a long and well-developed rostrum, for example members of the Neotropical genus Rhinomalus Gemminger in Harold, 1870. The antennae are 11-segmented, or rarely 10-segmented, and always well-developed and vary in form, for example very long and filiform in Mestolaemus longicornis Keftovitch, 1962, or shorter and filiform in, for example Rhobdophloeus horni Sharp, 1899, indistinctly clubbed, for example in Leptophloeus angustulus (LeConte, 1866) or distinctly clubbed, for example in the new-world genus Lathropus Erichson, 1845. They are often sexually dimorphic, varying in length or the proportion of various segments, or otherwise modified, for example the basal segments in males of tropical species of Cryptolestes Ganglbauer, 1899; in C. calabozus Thomas, 1988 or C. unicornis (Reitter, 1876), but probably most developed in C. diemensis (Blackburn, 1903) where the basal segment is large and arcuate; almost semicircular. Temples variable, sometimes long but almost always strongly constricted. Pronotum quadrate to elongate, generally broadest in front of the middle and strongly narrowed towards the base, the anterior and posterior angles are usually well-formed and sometimes produced. The surface is variously punctured, often strongly so, but the cuticle is generally smooth between, and there is at least one sub-lateral carina. The lateral margins vary greatly; Often smoothly sinuate but sometimes denticulate, for example in Mestolaemus Lefkovitch.... or the Palaearctic Laemophloeus monilis (Fabricius, 1787), in Odontophloeus Thomas, 1984 the lateral margin has four large teeth. Scutellum transverse to triangular. Prosternum broad and flattened with a broad process, the coxal cavities variable. Mesosternum short and broad, the coxal cavities broadly separated and usually opened laterally. Metasternum elongate, usually with a complete median longitudinal line. Anterior coxae obliquely transverse, mid coxae round and globular, hind coxae transverse. Elytra covering the abdomen and usually rounded at the apex, the humerus well-developed. Surface smooth to randomly punctured, or with variously developed striae, longitudinal carinae, pubescence or rows of stiff setae, but never with a scutellary striole. Femora well-developed, tibiae robust; often swollen and usually with strong equal or unequal apical spines, especially to the pro- and meso-tibiae. Tarsi in males usually 5-5-5, sometimes 5-5-4, in females 5-5-5; basal segments short. Claws well-developed.

The larvae are elongate, in most cases strongly flattened, narrowed both anteriorly and posteriorly, and with prominent urogomphi. Most species live under dead, decaying and fungoid bark or xylem, mostly on broadleaf trees, but occasionally on conifers. Some are synanthropic, occurring in food-processing and warehouse facilities. The larvae of some Cryptolestes species are unique among insects in having prosternal silk glands with which they spin a cocoon.

UK Species

Thirteen species are included on the British list, including seven species of Cryptolestes Ganglbauer, 1899:

  • C. capensis (Waltl, 1834) Stored products.

  • C. duplicatus (Waltl, 1839) Beneath deciduous bark. Scattered records, southern England. Especially London.

  • C. ferrugineus (Stephens, 1831) Stored products. Widespread throughout England and Wales.

  • C. pusilloides (Steel & Howe, 1952) Stored products. Southern England, Hampshire.

  • C. pusillus (Schönherr, 1817) Stored products; also in the wild. ‘Flat Grain Beetle’.  A few records from eastern England.

  • C. spartii (Curtis, 1834) From Cytissus (Broom). Scattered, south-East England.

  • C. turcicus (Grouvelle, 1876) Stored products.

  • Laemophloeus monilis (Fabricius, 1787) A few scattered records from southern England.

  • Leptophloeus clematidis (Erichson, 1846) Native, in Xylocleptes  galleries in Clematis vitalba. Thames basin and south-east coast.

  • L. janeti (Grouvelle, 1899) Occasional import from Africa in stored products.

  • L. alternans Erichson, 1846 Discovered in Surrey in 2015. Bark beetle galleries in conifers.

  • Notolaemus unifasciatus (Latreille, 1804) Scattered through southern and eastern England.

  • Placonotus testaceus (Fabricius, 1787) From Berks and east Suffolk, in deciduous woodland.

Cryptolestes capensis

C. duplicatus

C. pusilloides

C. spartii

C. turcicus

Notolaemus unifasciatus

Leptophloeus clematidis

L. janeti

L. alternans

Placonotus testaceus

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