Cerylonidae

Cerylon histeroides, copyright Dick Belgers.

Belongs within: Coccinelloidea.

The Cerylonidae are a group of small beetles found under bark of rotten logs and in decaying leaf litter where they probably feed on fungal hyphae and spores (Lawrence & Britton 1991). Robertson et al. (2015) excluded the subfamilies Murmidiinae and Euxestinae from the Cerylonidae, restricting the family to a clade including Ceryloninae and Ostomopsis. Ostomopsis is a distinctive genus with the antennal club emarginated laterally and bearing specialised sensilla, serrulate pronotal edges, and the apical flange of the elytra expanded (Robertson et al. 2015).

Minute, mysterious bark beetles

To re-iterate the point: the world is home to an awful lot of small brown beetles. Because of their tiny size and contingent obscurity, the habits of many of these small brown beetles remain little known. Case in point: the minute bark beetles of the Cerylonidae.

Cerylonids are typically minute, oval to elongate beetles (most are less than two millimetres in length) that are blackish or brownish in coloration, with a shiny body surface that often lacks conspicuous pubescence (Thomas 2002). The antennae are short with a compact club and inserted laterally on the head with insertions exposed. Tarsi are usually four-segmented (three-segmented in Ostomopsis) and the abdomen has five free ventrites. Cerylonids are found more or less worldwide but are most diverse in the tropics. As suggested by their vernacular name of ‘minute bark beetles’, they are typically found under bark or within leaf litter.

Ostomopsis sp., copyright Jim McClarin.

The exact scope of the family has been subject to some revision. Authors have differed over the years as to where exactly to draw the line between cerylonids and related small beetle families, most notably the Bothrideridae. A molecular phylogenetic analysis of the cerylonids and related families by Robertson et al. (2015) found the Cerylonidae in the broader sense to be non-monophyletic. As a result, a number of subfamilies previously treated as cerylonids were moved elsewhere, with Cerylonidae being cut back to just two: Ceryloninae and the isolated genus Ostomopsis (there’s also Loebliorylon, which has also been assigned its own subfamily close to Ceryloninae but was not analysed by Robertson et al.) Features shared by these two taxa include the lack of a median fleck on the hind wing, a narrow and parallel-sided intercoxal process between the fore coxae, and features of the ovipositor. Ceryloninae are further distinguished from other beetles by a crenulate margin on the last abdominal ventrite, absence of a frontoclypeal suture on the head, and a needle-like tip to the maxillary palps together with long, slender, blade- or needle-like laciniae and galeae on the maxillae themselves. The larvae of cerylonines have distinctive stylet-like mandibles that are either endognathous or contained within a tubular beak. Unfortunately, the larvae of Ostomopsis are as yet unknown.

Mychocerus astrolabei, copyright Udo Schmidt.

As indicated above, the exact habits of cerylonids are largely unknown. Thomas (2002) notes that they ‘apparently feed on fungi’ but that does raise questions about the exact function of the mouthparts. These seem to be modified in cerylonines for some sort of piercing behaviour. Are they also using them to stab unfortunate micro-animals that share their concealed environment? Or are they using them to pierce the outer surface of spores to gain access to the fluids within?

Systematics of Cerylonidae

Characters (from Lawrence & Britton 1991): Broadly ovate to narrowly elongate, slightly to strongly flattened, red to brown to black in colour (occasionally bicoloured), subglabrous or sparsely clothed with erect hairs. Antenna eight- to eleven-segmented, club almost always one- or two-segmented and compact (exceptionally three-segmented); fore coxae globose, trochantins concealed, fore coxal cavities open or closed internally and externally; mid coxae moderately to widely separated, cavities closed; hind coxae almost always widely separated; tarsi tri- or tetramerous; abdomen with five visible ventrites, all free, femoral lines often present on metasternum and/or ventrite 1. Larva elongate to broadly ovate and disc-like with lateral tergal processes on all thoracic and most abdominal segments and usually with granulate or tuberculate dorsal surface clothed with variously modified setae.

<==Cerylonidae [Cerylonides, Dolosidae, Pleosomidae]
| i. s.: Pakalukia napo Ślipiński 1991B14
| GlyptolopusB14
| LoebliorylonRS15
|--Ostomopsis Scott 1922T02 [OstomopsinaeMW15]
| `--O. neotropicalis Lawrence & Stephan 1975T02
`--CeryloninaeMW15
| i. s.: Cerylonopsis alienigenusLB91
| Cautomus mirabilisLB91
| Aculagnathus [Aculagnathidae]B74
| `--A. mirabilisB70
|--Philothermus Aubé 1843RS15, T02 (see below for synonymy)
| `--P. glabriculusMW15
`--+--Mychocerus Erichson 1845RS15, T02 (see below for synonymy)
| `--M. discretusRS15
`--+--Cerylon Latreille 1802RS15, T02 [incl. Aphardion Gozis 1886T02]
| |--*C. terebrans [=Lyctus terebrans]L02
| |--C. alienigerumB70
| |--C. castaneusT02
| |--C. histeroides [=Cis (Cerylon) histeroides]G20
| `--C. unicolorRS15
`--+--Australiorylon longipilisRS15, LB91
`--+--AfrorylonRS15
`--PhilothermopsisRS15

Mychocerus Erichson 1845RS15, T02 [incl. Brachylon Gorham 1898T02, Decalapethus Dajoz 1978T02, Lapecautomus Sen Gupta & Crowson 1973T02, Lapethus Casey 1890T02, Lytopeplus Sharp 1895T02]

Philothermus Aubé 1843RS15, T02 [incl. Batufia Dajoz 1978T02, Caecodium Dajoz 1974T02, Cerylcautomus Sen Gupta & Crowson 1973T02, Comalon Dajoz 1974T02, Kenyalon Dajoz 1974T02, Madacerylon Dajoz 1980T02, Neoglyptoides Dajoz 1976T02, Neoglyptus Dajoz 1974T02, Pologlyptus Dajoz 1974T02, Pseudophilothermus Dajoz 1973T02]

*Type species of generic name indicated

References

[B14] Bouchard, P. (ed.) 2014. The Book of Beetles: A lifesize guide to six hundred of nature’s gems. Ivy Press: Lewes (United Kingdom).

[B70] Britton, E. B. 1970. Coleoptera (beetles). In: CSIRO. The Insects of Australia: A textbook for students and research workers pp. 495–621. Melbourne University Press.

[B74] Britton, E. B. 1974. Coleoptera (beetles). In: CSIRO. The Insects of Australia: A textbook for students and research workers. Supplement 1974 pp. 62–89. Melbourne University Press.

[G20] Goldfuss, G. A. 1820. Handbuch der Naturgeschichte vol. 3. Handbuch der Zoologie pt 1. Johann Leonhard Schrag: Nürnberg.

[L02] Latreille, P. A. 1802. Histoire Naturelle, générale et particulière des crustacés et des insectes vol. 3. Familles naturelles des genres. F. Dufart: Paris.

[LB91] Lawrence, J. F., & E. B. Britton. 1991. Coleoptera (beetles). In: CSIRO. The Insects of Australia: A textbook for students and research workers 2nd ed. vol. 2 pp. 543–683. Melbourne University Press: Carlton (Victoria).

[MW15] McKenna, D. D., A. L. Wild, K. Kanda, C. L. Bellamy, R. G. Beutel, M. S. Caterino, C. W. Farnum, D. C. Hawks, M. A. Ivie, M. L. Jameson, R. A. B. Leschen, A. E. Marvaldi, J. V. McHugh, A. F. Newton, J. A. Robertson, M. K. Thayer, M. F. Whiting, J. F. Lawrence, A. Ślipiński, D. R. Maddison & B. D. Farrell. 2015. The beetle tree of life reveals that Coleoptera survived end-Permian mass extinction to diversify during the Cretaceous terrestrial revolution. Systematic Entomology 40 (4): 835–880.

[RS15] Robertson, J. A., A. Ślipiński, M. Moulton, F. W. Shockley, A. Giorgi, N. P. Lord, D. D. McKenna, W. Tomaszewska, J. Forrester, K. B. Miller, M. F. Whiting & J. V. McHugh. 2015. Phylogeny and classification of Cucujoidea and the recognition of a new superfamily Coccinelloidea (Coleoptera: Cucujiformia). Systematic Entomology 40: 745–778.

[T02] Thomas, M. C. 2002. Cerylonidae Billberg 1820. In: Arnett, R. H., Jr, M. C. Thomas, P. E. Skelley & J. H. Frank (eds) American Beetles vol. 2. Polyphaga: Scarabaeoidea through Curculionoidea pp. 363–365. CRC Press.

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