CERYLONIDAE Billberg, 1820
​Minute Bark Beetles
Includes three widespread saproxylic species and one established stored product pest. A second species associated with stored products is dubiously included on the British list.
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
2
2
5
1.5-2.5mm
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Introduction
These small beetles are unusual, though not unique e.g. see Eucinetidae, among the coleoptera in that most larvae and some adults possess piercing and sucking mouthparts. They have long been included as a group within the Colydiidae but they are very distinct from that family. Cerylonidae includes about 450 species in 52 genera and 5 subfamilies. They occur throughout the world but are most diverse in the tropics and wooded areas of the subtropics and the family includes a large number of local and island endemics.
Loeblioryloninae Slipinski, 1991 includes 11 species of the single genus Loebliorylon Slipinski, 1991 from Asia (Nepal and Bengal) and Southeast Asia (Thailand, Malaysia and Indonesia). They are atypical of the family and very characteristic species; elongate and discontinuous in outline with the entire dorsal surface strongly rugose and punctured, the pronotum is quadrate and broadest anteriorly and the elytra broadest behind the shoulders and strongly narrowed to a transverse apex. Each elytron with two strongly raised longitudinal carina. The legs are long and robust with broad femora, flattened tibiae which are expanded towards the apex and tiny tarsi.
Murmidiinae Jacquelin du Val, 1858 includes 3 genera. Botrodus Casey, 1890 includes 2 species from Mexico and North Vietnam. The monotypic Mychocerinus Slipinski, 1991 is Nearctic. Murmidius Leach, 1821 is a widespread genus with species from the Holarctic, Southeast Asia, Africa and the Neotropical zones, 2 stored product pests have been recorded from the U.K., M. segregatus Waterhouse, C. O., 1876, originally described from Rodrigues Island, and the cosmopolitan M. ovalis (Beck, 1817).
Euxestinae Grouvelle, 1908 includes 11 genera and about 70 species and is almost cosmopolitan. Some genera are restricted to a particular region e.g. Hypodacnella Slipinski, 1988 (10 spp.) and the monotypic Protoxestus Sen Gupta, 1973 from Australia, or Euxestoxenus Arrow, 1925 with about a dozen African species, while others are more widespread e.g. the pan-tropical Euxestus Wollaston, 1858 with about 20 species, of which one, E. peregrina (Belon, 1885), has been recorded from France. Metacerylon Grouvelle, 1906 includes 15 species from the Neotropical, African and Australian zones.
Ostomopsinae Sen Gupta & Crowson, 1973 is monogeneric with 2 species from Central America and the Seychelles.
Ceryloninae Billberg, 1820 is by far the largest subfamily with 36 genera and more than 380 species. Many groups are of restricted distribution and there are several monotypic endemics e.g. Coccilon Hinton, 1942 from Borneo, Neolapethus Sen Gupta & Pal, 1985 from Sri Lanka, and Ivieus Slipinski, 1991 and Pakulukia Slipinski, 1991 from Ecuador. The 5 species of Glyptolopus Erichson, 1845 are Neotropical and the 4 species of Australiorylon Slipinski, 1988 are Australian. Among the larger genera are Afrorylon Slipinski, 1980 with 13 species, and Elytrotetrantus John, 1941 with 40 species, both from Africa, Axiocerylon Grouvelle, 1918 with more than 25 species from Southeast Asia, Philothermopsis Heinze, 1944 with 25 species from Asia, Australia and Africa, and Philothermus Aubé, 1843 with more than 80 species, which is pantropical and also represented in the Nearctic and Asia and contains many island endemics including 18 from Madagascar. Cerylon Latreille, 1802 includes about 75 species and is pantropical, extending into the Holarctic, and with many island endemics.
Ecology
Most species are saproxylic, occurring under bark on both coniferous and broad-leaved trees in all stages of decay including fallen branches and decaying logs in just about any situation where both adults and larvae are thought to feed on fungal hyphae and spores etc. and slime-moulds. Some African species inhabit the borings of scolytids etc. probably developing on the fungi growing within. Some members of the Euxestinae are associated with fungus-cultivating termites, and a few species of Ceryloninae and Euxestinae are myrmecophilous. Murmidius ovalis is a cosmopolitan pest of stored foodstuffs contaminated with yeast or moulds.
Description
Cerylonidae is a very diverse group that is difficult to characterize in terms of morphological features that apply to the whole family. All are small, 0.8-4.5mm and moderately to strongly flattened, variously elongate e.g. Cerylon to almost circular e.g. Euxestoxenus, and continuous or discontinuous in outline. Species of several genera e.g. Euxestus or Hypodacne are smooth, convex and oval and might be mistaken for Phalacrids etc. All are drab, black to brown or red in colour and glabrous or nearly so, long pubescence being present in only a few. Head proportionally small and deeply inserted into the thorax, generally to the level of the eyes; concave or flattened to weakly convex in a few e.g. Philothermus Aubé, 1843. Frontoclypeal suture present (Murmidiinae, Ostomopsinae and Euxestinae) or absent (Ceryloninae and Loeblioryloninae) and often with a transverse occipital ridge. Labrum unmodified and transverse to elongate, or elongate and pointed in piercing species, mandibles with 2 or 3 apical teeth, a prosthecal fringe and a prominent mola, or modified and sharp or blade-like in piercing species. Maxillary and labial palpi geniculate, in many with the terminal segment reduced. Antennae generally short and inserted laterally in front of the eyes, the insertions visible from above, 6-11 segmented, with less than 11 in most species; basal segment enlarged, intermediate segments transverse to quadrate, and with a 1-3 segmented club. The pedicel is mounted ventrally on the basal segment. Pronotum transverse to quadrate, rarely slightly elongate, broadest at the base and narrowed anteriorly, or broadest about the middle and evenly curved or sinuate so that the base is narrower than the elytra across the shoulders, evenly convex and smooth or, often, with a pair of basal fovea or an antennal cavity behind the anterior angle, sometimes bordered and narrowly explanate laterally e.g. Philothermus. Basal margin straight e.g. in Cerylon, to strongly sinuate e.g. in Mychocerus Erichson, 1845. Punctation varies from fine and sparse to strong and moderately dense. Prosternum long anterior to small and rounded coxal cavities, anterior angles and hypomera with antennal cavities in some species. Anterior coxae open or closed posteriorly, moderately to widely separated and with concealed lateral extensions, the prosternal process often broad and flat. Mesocoxal cavities transverse, closed laterally by sterna and moderately to widely separated. Metacoxae transverse and sometimes widely separated, metasternum sometimes with femoral lines and often produced around the mesocoxae. Wings often well-developed but lacking a radial cell. Abdomen with 5 free sternites, the first much longer than the others and often with femoral lines. Spiracles present on segments 1-5 or 1-7 in Euxestinae. Apical margin of the terminal segment crenulate in Murmidiinae, Ostomopsinae and Ceryloninae. Scutellum visible, usually small, and quadrate to elongate and pointed. Elytra completely covering the abdomen and continuously rounded apically, smoothly rounded to almost parallel-sided, and with well-developed epipleura which are broad at the base and usually continue to the apex. Shoulders evenly convex, not prominent, and sometimes with a small tooth. Each with up to 8 impressed and complete striae which are variously punctured, and flat to convex or carinate interstices which are smooth or only finely punctured, glabrous to finely pubescent, rarely with outstanding pubescence e.g. Ostomopsis neotropicalis Lawrence & Stephan, 1975. Lateral margins usually bordered, and sometimes e.g. in Euxestoxenus Arrow, 1925, narrowly explanate. Legs short and slender with elongate trocanters and weakly thickened femora, short and stout tibiae which are only weakly expanded apically and generally with 1 or 2 apical spurs. Tarsi 4-4-4 or 3-3-3; segments simple or, rarely, the basal segment is lobed. Claws simple.
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Larvae are flattened and elongate to oval with the head inclined to strongly hypognathous and without impressed frontal sutures. Antennae short and 3-segmented with sensory appendages on segment 2 longer than the terminal segment. Mouthparts normal or adapted to piercing. Legs short and with a single stiff seta. Prothorax large and often covering the head. Abdominal segment 9 short and with or without urogomphi.
A key to the UK species can be found HERE.
UK Species
The U.K. list includes 5 species in 2 genera. Our 3 species of Cerylon are saproxylic, occurring under bark, while Murmidius ovalis (Beck, 1817) is a pest of stored foodstuffs, particularly rice. The 2 genera are obvious from their general appearance.
