Micridium Motschulsky, 1869

Darby, Michael, 2017, Taxonomic review of the genera Micridium Motschulsky, 1869 and Micridina Johnson, 1969 (Coleoptera: Ptiliidae) with eleven new species including the first records from South America and Madagascar, Zootaxa 4242 (2), pp. 233-254 : 236-237

publication ID	https://doi.org/10.11646/zootaxa.4242.2.2
publication LSID	lsid:zoobank.org:pub:0DD1868D-4EF5-4FB7-AEE9-372644800A79
DOI	https://doi.org/10.5281/zenodo.6045179
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scientific name	Micridium Motschulsky, 1869
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Genus Micridium Motschulsky, 1869 View in CoL

Micridium Motschulsky, 1869 View in CoL . Type species Trichopteryx vittata Motschulsky, 1845 .

Dilinium Casey, 1924 View in CoL . Type species Dilinium rhodeanum Casey, 1924 View in CoL . Synonymised by Johnson (2001). Micridina Johnson, 1969 View in CoL . Type species Micridina hilli Johnson, 1969 View in CoL . Syn. nov.

Diagnosis. Narrow, moderately convex, somewhat shining and finely pubescent insects, distinguished by the possession of carinae following the line of the mesoventral/mesepiventral suture (Figs. A, 47–60). Reticulation cells oriented to follow the same line occur not uncommonly in other members of the family but without forming distinct parallel sided carinae. When the suture is more marked a single line is usually present as in some members of the Nanosellini and Discheramocephaliini which are quickly separated from Micridium by the criteria distinguishing those tribes. ( Hall 1999; Grebennikov 2008; Grebennikov 2009; Darby 2016).

Additional non-diagnostic characters are as follows: antennae with 11 antennomeres, 1 & 2 enlarged to form a pedicel, 3–8 either ovoid or elongate, 9–11 a loosely jointed club, 10 & 11 with sensillae either single or branched ( Figs. 42–46 View FIGURES 42 – 46 ). Pronotum with or without a pair of linear depressions (never with either a single median linear depression or three linear depressions) and either additionally or independently with or without groups of setal pits. ( Figs. 17–32 View FIGURES 17 – 32 ). Mentum either +/– square widened at anterior margin ( Figs. 39–41 View FIGURES 33 – 41 ) or straight sided and clearly narrowed towards base ( Figs. 33–38 View FIGURES 33 – 41 ). Submentum usually with 3, rarely 4 setae. Scutellum base curved with or without two or more basal pits ( Figs. 100–101 View FIGURES 100 – 101 ). Elytral humeri with or without semi–circular setal pits, sutural margin entire.

Mesoventrum with two carinae following the lines of the mesoventral/mesepiventral sutures (Fig. A). Mesoventral keel sometimes extending between the mesocoxae for a short distance onto the metaventrum ( Fig. 48, 56 View FIGURES 47 – 60 ), and anteriorly to the mesoventral collar, the anterior extension sometimes widened and split medially to form two separate carinae ( Fig. 59 View FIGURES 47 – 60 ). Mesocoxae either almost contiguous ( Figs. 48, 49, 50, 56 View FIGURES 47 – 60 ) or separated by as much as +/– half their width ( Figs. 47, 53, 57, 58 View FIGURES 47 – 60 ). Mesoventral collar, extending onto the humeri which, if present, are either rounded or, more often, toothed. Mesepiventrum with or without distinct reticulation, posterior angles smoothly rounded ( Figs. 50, 56, 58 View FIGURES 47 – 60 ) or angled strongly ( Fig. 53 View FIGURES 47 – 60 ) or slightly ( Figs. 49, 55 View FIGURES 47 – 60 ).

Metaventrum with or without clear reticulation, with distinct metepiventral sutures running posteriorly from the sides of the mesoventrum parallel to the lateral margins or turning inwards posteriorly, either short, or long sometimes reaching the metacoxae ( Figs. 61–71 View FIGURES 61 – 71 ); the posterior intercoxal process with two small teeth at the corners (Fig. 95), lacking in some males which possess a fringe of 4–30 flattened setae sometimes extending as far as the posterior margin of the metacoxal plates ( Figs. 91–94, 96–99).

Abdomen with six visible ventrites. Pygidium composed of tergites IX and X which are not fused, X with a strong apical tooth (Fig. 102).

Wings of usual ptiliid form either present or absent.

References

Casey, T. L. (1924) Additions to the known Coleoptera of North America. In Memoirs on the Coleoptera. Uol. 11. Lancaster Press, Lancaster, Pa., 347 pp.

Grebennikov, V. V. (2008) How small can you go: Factors limiting body miniaturization in winged insects with a review of the pantropical genus Discheramocephalus and description of six new species of the smallest beetles (Pterygota: Coleoptera: Ptiliidae). European Journal of Entomology, 105, 313 - 328.

Grebennikov, V. V. (2009) Discheramocephalini, a new pantropical tribe of featherwing beetles (Coleoptera: Ptiliidae): description of new taxa and phylogenetic analysis. Systematic Entomology, 34, 113 - 136. https: // doi. org / 10.14411 / eje. 2008.039

Hall, W. E. (1999) Generic Revision of the Tribe Nanosellini (Coleoptera: Ptiliidae: Ptiliinae). Transactions of the American Entomological Society, 12, 39 - 123.

Johnson, C. (1969) A new genus and species of Ptiliidae (Col) from Tamana Cave, Trinidad. Entomologist, 102, 145 - 148.

Johnson, C. (2001) Notes of Palearctic Ptiliidae (Coleoptera). Entomologists's Gazette, 52, 129 - 137.

Motschulsky, V. (1845) Ueber die Ptilien Russlands. Bulletin de la Societe Imperiale des Naturalistes de Moscou, 18 (4), 504 - 539, pls. 9 - 10.

Motschulsky, V. (1869) Enumeration des nouvelles especes de Coleopteres rapportes de ses voyages. 6 - ieme Article. Bulletin de la Societe Imperiale des Naturalistes de Moscou, 41, 170 - 201, pl. 8.

Figures

FIGURES 42 – 46. Micridium antennae. 42. M. quadridens sp. n. showing more rounded antennomeres on shorter antennae. 43. M. thayerae sp. n. 44. M. elegans sp. n. showing more elongate antennomeres. 45. M. johnsoni sp. n. x 2000 antennomeres 9 – 11 showing single sensillae on 10 & 11. 46. M. foveatum sp. n. x 1800 antennomeres 10 & 11 showing branched sensillae.

FIGURES 17 – 32. Micridium pronotums. 17. M. quadridens sp. n. x 605. 18. M. inornatum sp. n. x 590. 19. M. boliviense sp. n. x 625. 20. M. newtoni sp. n. x 695. 21. M. foveatum sp. n. x 830. 22. M. johnsoni sp. n. x 790. 23. M. elegans sp. n. x 810. 24. M. thayerae sp. n. x 650. 25. M. halidaii (Matthews) x 770. 26. M. hilli (Johnson) x 740. 27. M. oweni sp. n. x 575. 28. M. attenboroughi sp. n. x 675. 29. M. angulicolle (Fairmaire). 30. M. rhodeanum (Casey) 31. M. vittatum Motschulsky 32. M. lineatum Le Conte.

FIGURES 33 – 41. Micridium mentums. 33. M. oweni sp. n. x 1420. 34. M. attenboroughi sp. n. x 1840. 35. M. boliviense sp. n. x 1280. 36. M. elegans sp. n. x 1320. 37. M. proprium sp. n. x 2360. 38. M. quadridens sp. n. x 1900. 39. M. johnsoni sp. n. x 1600. 40. M. foveatum sp. n. x 1220. 41. M. thayerae sp. n. x 1160.

FIGURES 100 – 101. Micridium scutellums. 100. M. newtoni sp. n. x 695. 101. M. halidaii (Matthews) x 1640. FIGURE 102. Micridium foveatum sp. n. apical point of pygidium.

FIGURES 47 – 60. Micridium mesoventra. 47. M. inornatum sp. n. x 540. 48. M. quadridens sp. n. x 710. 49. M. boliviense sp. n. x 695. 50. M. attenboroughi sp. n. x 870. 51. M. proprium sp. n. x 920. 52. M. newtoni sp. n. 53. M. johnsoni sp. n. x 655. 54. M. thayerae sp. n. x 860. 55. M. halidaii (Matthews) x 615. 56. M. oweni sp. n. x 585. 57. M. elegans sp. n. x 705. 58. M. hilli (Johnson) x 760. 59. M. foveatum sp. n. x 1300. 60. M. rhodeanum (Casey) x 545.

FIGURES 61 – 71. Micridium metepiventral sutures. 61. M. johnsoni sp. n. x 530. 62. M. thayerae sp. n. x 505. 63. M. attenboroughi sp. n. x 670. 64. M. foveatum sp. n. x 735. 65. M. quadridens sp. n. x 710. 66. M. elegans sp. n. x 730. 67. M. oweni sp. n. x 585. 68. M. hilli (Johnson) x 760. 69. M. halidaii (Matthews) x 615. 70. M. newtoni sp. n. x 710. 71. M. rhodeanum (Casey) x 545.