Xanthocomus Guillebeau, 1893

Gimmel, Matthew L., 2013, <strong> Genus-level revision of the family Phalacridae (Coleoptera: Cucujoidea) </ strong>, Zootaxa 3605 (1), pp. 1-147 : 42-43

7. Xanthocomus Guillebeau, 1893

( Figs. 2m ; 11 ; 38d, e )

Xanthocomus Guillebeau 1893 a: 291 . Type species: Xanthocomus striatus Guillebeau 1893 , fixed by subsequent designation. Leptostilbus Casey 1916: 71 . Type species: Leptostilbus rutilans Casey 1916 , fixed by subsequent designation ( Gimmel 2011:

2). [synonymized with Xanthocomus Guillebeau by Gimmel (2011: 2)]

Type material. Xanthocomus striatus Guillebeau : two syntypes, including one dissected male, here designated as a lectotype to stabilize the species and generic names, “Caracas // Simon // Museum Paris, collection genérale // TYPE // [unpublished lectotype label, turned over] // GENITALIA IN DMHF — WATER SOLUBLE MEDIUM // striatus Guilb. // LECTOTYPE \ Xanthocomus \ striatus Guillebeau \ des. M.L. Gimmel 2011 [red label]” ( MNHN). Paralectotype, also “Caracas // Simon…”, with label attached “ PARALECTOTYPE \ Xanthocomus \ striatus Guillebeau \ det. M.L. Gimmel 2011 [yellow label]” ( MNHN).

Leptostilbus rutilans Casey : lectotype, point-mounted male with genitalia dissected out and mounted in DMHF on an acetate card on the same pin, “ Brownsville \ Texas \ Wickham // CASEY \ bequest \ 1925 // rutilans 7 \ PARATYPE USNM \ 48982 [epithet and numbers handwritten] [red label] // LECTOTYPE \ Leptostilbus \ rutilans Casey \ des. M.L. Gimmel 2010 [red label]” ( USNM) .

Diagnosis. May be recognized by the divergent, arcuate metaventral postcoxal lines, single elytral sutural stria, metatarsomere I shorter than II and joint between them more or less rigid, prosternal process angulate when viewed laterally and with row of stiff setae at apex, mandible with a ventral ridge, the obliquely oriented setose groove behind eye ventrally, the tegmen with parameres hinged to basal piece, and the elongate, usually reddish-colored habitus.

Description. Small to large, total length 1.6–3.4 mm. Dorsal color dark reddish to reddish-testaceous ( Fig. 38d, e ). Tibial spur formula 2-2-2, tarsal formula 5-5- 5 in females, 5-5- 4 in males.

Head. Not constricted behind eyes. Eyes small to medium sized; facets flat; interfacetal setae absent; weakly emarginate medially; without sharp posterior emargination; periocular groove present; with obliquely oriented setose groove ventrally behind eye ( Fig. 2m ). Frontoclypeus emarginate above antennal insertion; clypeal apex arcuate-truncate. Antennal club 3-segmented, club weakly asymmetrical, antennomere XI not constricted ( Fig. 11b ). Mandible ( Fig. 11a ) with apex bidentate; with retinaculum; mandible with ventral ridge and deep pocket. Maxillary palpomere IV fusiform, inner edge swollen medially; galea short, rounded; lacinia with two stout spines, often with associated tuft of setae . Mentum with sides divergent toward apex; labial palpomere III fusiform. Labrum with apical margin arcuate to truncate. Gular sutures long .

Thorax. Pronotum with or without obvious microsetae; with scutellar lobe absent or weakly developed. Prosternum anteriorly with marginal setae distributed in two patches, setae normal; procoxal cavity with anterolateral notchlike extension; prosternal process angulate in lateral view, not conspicuously setose preapically, with row of spinelike setae at apex. Protrochanter without setae; protibia without ctenidium on kickface ( Fig. 11c ). Scutellar shield small. Elytron without or with moderate spectral iridescence; one sutural stria present; discal striae unimpressed, but usually represented by rows of distinct, round punctures; without transverse strigae; lateral margin with row of tiny, sawtooth-like setae. Mesoventral plate ( Fig. 11f ) notched anteriorly, extending posteriorly to metaventrite, dividing mesoventral disc in two, forming distinct procoxal rests; mesanepisternum with incomplete transverse carina; mesocoxal cavities widely separate, separated by more than half width of a coxal cavity. Mesotarsomere III bilobed. Metaventral process ( Fig. 11f ) not extending anteriorly beyond anterior level of mesocoxae; metaventral postcoxal lines diverging from mesocoxal cavity margin, arcuate and smoothly rounded; discrimen short, extending less than halfway to anterior margin of metaventral process; metendosternite ( Fig. 11g ) with anterior tendons moderately separated, ventral process intersecting ventral longitudinal flange behind anterior margin. Anterior margin of metacoxa with emargination sublaterally; metacoxal plate with transverse line present or absent; metatibial foreface with apical ctenidium roughly perpendicular overall to long axis of tibia; spurs cylindrical, longest spur shorter than width of tibial apex, spurs sometimes weakly modified in males; metatarsomere I distinctly shorter than metatarsomere II, joint between I and II rigid ( Fig. 11d ). Hind wing ( Fig. 11e ) with distinct, ovate anal lobe; leading edge with complete row of long setae at level of RA +ScP; AA 3+4 not apparent; cubitoanal system sometimes branched apically; CuA 2 and MP 3+4 without distal remnants; r4 present or absent; flecks absent from apical field distal to rp-mp2; long transverse proximal sclerite and additional weak, irregular sclerite present just distal to end of radial bar.

Abdomen. Abdominal ventrite I without paired lines or calli; spiracles apparently absent from segment VII. Male with aedeagus upright in repose; tegmen ( Fig. 11h ) with symmetrical anterior margin, parameres hinged to basal piece, parameres with medial longitudinal division; penis ( Fig. 11i ) slender, with endophallic spicules, often with large sclerites, apex with three or five small points; spiculum gastrale V-shaped, with arms free. Female ovipositor weakly sclerotized, palpiform.

Immature stages. Unknown.

Bionomics. Members of this genus have been swept from grassy meadows. They probably feed on microfungi growing on dead grasses.

Distribution and diversity. Occurring from the northern United States (Massachusetts to Michigan and Wisconsin) south to Argentina. They are a conspicuous faunal element in the West Indies.

Included species (11):

Xanthocomus attenuatus (Casey, 1890) , comb. nov. ( Stilbus ) ( Distribution : USA) (type!)

Xanthocomus badius Guillebeau, 1893 ( Distribution : Venezuela) (type!)

Xanthocomus distinctus ( Sharp, 1888) , comb. nov. ( Leptostilbus ) ( Distribution : Guatemala) (type!)

Xanthocomus floralis Guillebeau, 1894 ( Distribution : Cuba) (type!)

Xanthocomus gracilis ( Sharp, 1888) , comb. nov. ( Stilbus ) ( Distribution : Belize, Guatemala) (type!)

Xanthocomus grouvellei Guillebeau, 1894 (Distribution: Haiti)

Xanthocomus rufescens Guillebeau, 1894 ( Distribution : Brazil) (type!)

Xanthocomus rufus Guillebeau, 1893 ( Distribution : Venezuela) (type!)

Xanthocomus rutilans ( Casey, 1916) (Distribution: USA, Central America, South America, West Indies) (type!)

Xanthocomus striatus Guillebeau, 1893 ( Distribution : Venezuela) (type!)

Xanthocomus vicinus Guillebeau, 1893 ( Distribution : Venezuela) (type!)

Discussion. The species of this genus were recently revised for North America ( Gimmel 2011). Recent examination of types nominally described in Stilbus in the Casey collection has revealed three new synonymies:

Stilbus attenuatus Casey, 1890 = Xanthocomus concinnus ( Casey, 1916) ; Stilbus thoracicus Casey, 1916 ; Stilbus quadrisetosus Casey, 1916 , syn. nov.

The valid name for this species becomes Xanthocomus attenuatus ( Casey, 1889) .

The species of Xanthocomus from south of the United States are still in need of revision.

Figures

FIGURE 2. Key characters for Phalacridae. (a) Schematic of dorsal characters showing small scutellar shield and two sutural striae. (b) Schematic of dorsal characters showing large scutellar shield and one sutural stria. Frontal view of head capsule of (c) Stilbus; (d) Phalacrus; (e) Tolyphus. (f) Maxillary palpus of Megistopalpus. Labial palpus of (g) Grouvelleus; (h) Phalacrinus (scale bar = 0.5 mm); (i) Phaenocephalus (scale bar = 0.2 mm). Dorsal view of head capsule of (j) Phaenocephalus; (k) Phalacrinus; (l) Acylomus (scale bars = 0.5 mm). Ventral view of head capsule of (m) Xanthocomus; (n) Nesiotus.

FIGURE 11. Xanthocomus striatus, male. (a) Left mandible, dorsal; (b) left antenna (scale bar = 0.5 mm). (c) Left protibia and tarsus, dorsal; (d) left metatibia and tarsus, ventral (scale bar = 0.5 mm). (e) Hind wing (scale bar = 1.0 mm). (f) Meso- and metaventrite, ventral (scale bar = 0.5 mm). (g) Metendosternite (scale bar = 0.5 mm). (h) Tegmen, ventral; (i) penis, ventral (scale bar = 0.5 mm).

FIGURE 38. Photographs. Nesiotus n.sp.: (a) dorsal. Stilbus nr. apicalis, male: (b) dorsal; (c) ventral. Xanthocomus sp.: (d) dorsal; (e) ventral. Pseudolibrus sp.: (f) dorsal. Litostilbus testaceus: (g) dorsal; (h) ventral. Litostilbus sp., southeast Asia: (i) dorsal.