Scydmaeninae

Microscydmus, copyright Edenis.

Belongs within: Staphylinidae.
Contains: Euconnini.

The Scydmaeninae, ant-like stone beetles, are a group of minute beetles found in habitats such as leaf litter or moss, or in association with ants or termites (O'Keefe 2001). Though long treated as their own family, more recent phylogenetic studies have established that they are derived within the Staphylinidae and they are now treated as a subfamily within that larger grouping.

Characters (from O'Keefe 2001, as Scydmaenidae): Body elongate, slender to ovoid; slightly to very convex, 0.6–2.7 mm long; often distinctly constricted between head and pronotum and between pronotum and elytra, usually light to dark brown, sometimes black in color; often densely pubescent on head, pronotum, and elytra, pubescence usually long. Head short and broad to ovoid; deflexed; usually distinctly constricted between vertex and occiput; occiput formed into a “neck”; clypeofrontal region moderate in length, slightly narrowed anteriorly. Eyes anterior, median, or posterior; moderate in size or absent. Antennae inserted anterior to eyes, antennal insertions adjacent to widely separated; antennae composed of scape, pedicel and nine flagellomeres; antennal club composed of distal three to five antennomeres, from indistinct to distinct in form. Mandibles usually planar, subtriangular with large basal area, narrowed to acute incisor, subapical teeth usually absent. Maxillary palpus composed of four palpomeres; palpomere III large, clavate; palpomere IV variable, distinctly smaller than III; apices of lacinea and galea densely covered with long setae. Labial palpus composed of three palpomeres; mentum large. Thorax with pronotum distinctly wider than head, usually with fovea or transverse furrow along posterior margin. Scutellum small, visible, occasionally hidden. Elytra ovoid, convex to rectangular, flat; humeri varied in form with 0-2 basal foveae in broad basal impression; elytral apices usually entire, occasionally truncate or fused. Hind wings, if present, well-developed. Legs relatively short to moderate in length; procoxae projecting beyond prosternum, procoxal cavities open; mesocoxal cavities closed; trochanters relatively large and sublinear or rounded triangular; femora strongly clavate in distal half; protibiae and mesotibiae usually with dense patches of setae at distal end. Prosternum varied from subquadrate to very narrow before conical, contiguous procoxae, pubescence varied. Mesosternum usually raised, sometimes densely setose, bearing mid-ventral carina separating otherwise contiguous mesocoxae. Metasternum long, broad, occasionally carinate or medially excavate; metacoxae round to transverse, conical, widely separate to contiguous. Abdomen with six visible sternites. Male genitalia with median lobe bulbous, large, to elongate, to reduced, lightly sclerotised, distinctly curved, parameres long, slender, articulated on dorsal surface of aedeagus, occasionally absent. Ovipositor composed of paired, fused or unfused dorsolateral paraprocts, triangular dorsal proctiger, paired elongate ventral valvifers, paired elongate gonocoxae; gonostyli absent; spermatheca present, variable in shape from elongate, slender to spherical, accessory gland sometimes present.

<==Scydmaeninae [Anisosphaeridae, Scydmaenidae, Scydmaenides] B14
    |  i. s.: Adrastia MW15
    |         Phagonophana B70
    |         Heterognathus myrmecophilus B70
    |         Syndicus [Syndicini] LB91
    |         Palaeostigus Newton 1982 GN09
    |           `--P. bifoveolatus (Boheman 1851) GN09
    |         Palaeoleptochromus GN09
    |--Hapsomela [Hapsomelinae, Hapsomelitae] GN09
    |--Mastigitae [Mastiginae] GN09
    |    |--Leptomastacini GN09
    |    |--Mastigini GN09
    |    `--Clidicini GN09
    |         |--Clidicus AY04
    |         `--Papusus Casey 1897 O01
    |              `--P. macer O01
    `--Scydmaeinitae GN09
         |  i. s.: Cephenniini GN09
         |           |--Coatesia LB91
         |           |--Neseuthia LB91
         |           |--Chelonoidum Strand 1935 [=Chelonoides Croissandeau 1894] O01
         |           |    `--C. corporosum O01
         |           `--Cephennium Müller & Kunze 1822 O01
         |                |--C. anophthalmicum O01
         |                `--C. thoracicum (Müller & Kunze 1822) B14
         |         Plaumanniolini GN09
         |         Chevrolatia Jacquelin du Val 1850 O01 [Chevrolatiini GN09]
         |           |--C. amoena LeConte 1866 B14
         |           `--C. occidentalis B14
         |         Leptoscydmus Casey 1897 O01 [Leptoscydmini GN09]
         |           `--L. caseyi O01
         |--Scydmaenini LB91
         |    |--Palaeoscydmaenus LB91
         |    |--Ceramphis Casey 1897 O01
         |    |    `--C. deformata O01
         |    `--Scydmaenus Latreille 1802 GN09 (see below for synonymy)
         |         |--S. angustatus Lucas 1846 E12
         |         |--S. hellwigii [=Pselaphus hellwigii] L02
         |         |--S. motschulskii O01
         |         |--S. myrmecophilus LB91
         |         |--S. nanus Lucas 1846 E12
         |         `--S. schaumii Lucas 1846 E12
         `--+--+--Euconnini GN09
            |  `--+--Cephennodes Reitter 1884 GN09
            |     `--Eutheiini O01
            |          |--Eutheia Stephens 1830 [=Euthia Agassiz 1847; incl. Euthiopsis Müller 1925] O01
            |          |--Euthiconus Reitter 1881 [incl. Ascydmus Casey 1897, Euthiodes Brendel 1893] O01
            |          |    `--E. lata O01
            |          `--Veraphis Casey 1987 GN09
            |               `--V. cristata O01
            `--Cyrtoscydmini MW01
                 |--Neuraphus MW01
                 |--Parascydmus Casey 1897 O01
                 |--Brachycepsis Brendel 1889 O01
                 |    `--B. subpunctatus O01
                 |--Catalinus Casey 1897 O01
                 |    `--C. angustus O01
                 |--Lophioderus Casey 1897 O01
                 |    `--L. arcifer O01
                 |--Taphroscydmus Casey 1897 O01
                 |    `--T. californicus O01
                 |--Stenichnus Thomson 1859 GN09 [incl. Cyrtoscydmus Motschulsky 1870 O01]
                 |    |--S. perforatus O01
                 |    `--S. turbatus Casey 1897 GN09
                 `--Microscydmus Saulcy & Croissandeau 1893 O01
                      |--M. (Microscydmus) [incl. Opresus Casey 1897] O01
                      |    `--M. misellus O01
                      |--M. (Delius Casey 1897) O01
                      |    `--M. (D.) robustulus O01
                      `--M. (Neladius Casey 1897) O01
                           `--M. (N.) tenuis O01

Scydmaenus Latreille 1802 GN09 [incl. Acholerops Casey 1897 O01, Eumicrus LaPorte 1840 O01, Microstemma Motschulsky 1858 O01]

*Type species of generic name indicated

REFERENCES

[AY04] Austin, A. D., D. K. Yeates, G. Cassis, M. J. Fletcher, J. La Salle, J. F. Lawrence, P. B. McQuillan, L. A. Mound, D. J. Bickel, P. J. Gullan, D. F. Hales & G. S. Taylor. 2004. Insects ‘Down Under’—diversity, endemism and evolution of the Australian insect fauna: examples from select orders. Australian Journal of Entomology 43 (3): 216–234.

[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.

[E12] Evenhuis, N. L. 2012. Publication and dating of the Exploration Scientifique de l’Algérie: Histoire Naturelle des Animaux Articulés (1846–1849) by Pierre Hippolyte Lucas. Zootaxa 3448: 1–61.

[GN09] Grebennikov, V. V., & A. F. Newton. 2009. Good-bye Scydmaenidae, or why the ant-like stone beetles should become megadiverse Staphylinidae sensu latissimo (Coleoptera). European Journal of Entomology 106: 275–301.

[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 2^nd 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.

[MW01] Molleman, F., & D. E. Walter. 2001. Niche segregation and can-openers: scydmaenid beetles as predators of armoured mites in Australia. In: Halliday, R. B., D. E. Walter, H. C. Proctor, R. A. Norton & M. J. Colloff (eds) Acarology: Proceedings of the 10^th International Congress pp. 283–288 Publishing: Melbourne.

[O01] O’Keefe, S. T. 2001. Scydmaenidae Leach, 1915. In: Arnett, R. H., Jr & M. C. Thomas (eds) American Beetles vol. 1. Archostemata, Myxophaga, Adephaga, Polyphaga: Staphyliniformia pp. 259–267. CRC Press: Boca Raton.

Last updated: 27 January 2019.