Micridium Motschulsky 1869
Creators: name: Darby, Michael
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Ptiliidae
Micridium

description: Genus Micridium Motschulsky, 1869
Micridium Motschulsky, 1869. Type species Trichopteryx vittata Motschulsky, 1845.
Dilinium Casey, 1924. Type species Dilinium rhodeanum Casey, 1924. Synonymised by Johnson (2001). Micridina Johnson, 1969. Type species Micridina hilli Johnson, 1969. 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). 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). Mentum either +/– square widened at anterior margin (Figs. 39–41) or straight sided and clearly narrowed towards base (Figs. 33–38). Submentum usually with 3, rarely 4 setae. Scutellum base curved with or without two or more basal pits (Figs. 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), and anteriorly to the mesoventral collar, the anterior extension sometimes widened and split medially to form two separate carinae (Fig. 59). Mesocoxae either almost contiguous (Figs. 48, 49, 50, 56) or separated by as much as +/– half their width (Figs. 47, 53, 57, 58). 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) or angled strongly (Fig. 53) or slightly (Figs. 49, 55).
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); 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.
description: Published as part of 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, pp. 233-254 in Zootaxa 4242 (2) on pages 236-237, DOI: 10.11646/zootaxa.4242.2.2, http://zenodo.org/record/376374