Stilbus Seidlitz, 1872

Gimmel, Matthew L., 2013, <strong> Genus-level revision of the family Phalacridae (Coleoptera: Cucujoidea) </ strong>, Zootaxa 3605 (1), pp. 1-147 : 38-42

6. Stilbus Seidlitz, 1872

( Figs. 2c ; 10 ; 38b, c )

Olistherus Seidlitz 1872: 157 . Type species: Silpha atomaria Linné 1767 , fixed by subsequent designation. [junior homonym of Olistherus Agassiz, 1846 ]

Stilbus Seidlitz 1872: 35 . Type species: Anisotoma testacea Panzer 1797 , fixed by subsequent designation. [replacement name for Olistherus Seidlitz, 1872 ]

Eustilbus Sharp 1888: 253 . Type species: Anisotoma testacea Panzer 1797 , fixed by objective synonymy with Stilbus Seidlitz. [unjustified replacement name for Stilbus Seidlitz, 1872 ]

Stilboides Guillebeau 1894 a: 282 . Type species: Stilboides sublineatus Guillebeau 1894 , fixed by original designation. [synonymized with Stilbus Seidlitz by Švec (2003: 101)]

Microstilbus Guillebeau 1894 a: 283 . Type species: Phalacrus nitidus Melsheimer 1844 , fixed by original designation.

Type material. Silpha atomaria Linné : type in LSUK, not seen .

Anisotoma testacea Panzer : types not seen.

Stilboides sublineatus Guillebeau : syntype, male, genitalia dissected, “Grouvelle [handwritten] // St. Domingue [handwritten] // Museum Paris \ collection genérale // HOLOTYPE [red label] // sublineatus Guilb. [handwritten] // Stilbus SUBLINEATUS (Guilb.) \ Svec det. 1992” ( MNHN). Guillebeau mentioned four examples in his original description, and this specimen would probably best be considered a lectotype. This will be addressed in a future publication.

Phalacrus nitidus Melsheimer : 3 syntypes, lectotype here designated, with the following labels: “[blue disc] // nitidus \ M. \ Pa. [handwritten] // LECTOTYPE \ Phalacrus \ nitidus Melsheimer \ des. M.L. Gimmel 2010 [red label]” ( MCZ). Three paralectotypes ( MCZ): one belongs to Leiodidae (Colenis) with the labels “Melsh. // [red square, placed on pin by S. Henshaw]”, and two paralectotypes are mounted on the same pin with the label “Melsh.”, each with label added “ PARALECTOTYPE \ Phalacrus \ nitidus Melsheimer \ det. M.L. Gimmel 2010 [yellow label]”. The lectotype is designated to prevent future doubts about the name.

Diagnosis. May be recognized by the divergent, angulate or one-branched metaventral postcoxal lines, single elytral sutural stria, metatarsomere I shorter than II with joint between them flexible, prosternal process angulate when viewed laterally and with row of stiff setae at apex, ventral lobe of the eye not expanded, mandible without a ventral ridge, and the tegmen with parameres fused to basal piece.

Description. Very small to medium-sized, total length 1.1–2.5 mm. Dorsal color reddish-testaceous to piceous, often with elytral apices paler ( Fig. 38b, c ). Tibial spur formula 2-2-2, tarsal formula 5-5- 4 in both sexes.

Head. Not constricted behind eyes. Eyes small to medium sized; facets flat; interfacetal setae absent; not emarginate medially; without sharp posterior emargination; periocular groove present; with transverse setose groove ventrally behind eye. Frontoclypeus ( Fig. 2c ) emarginate above antennal insertion; clypeal apex arcuatetruncate. Antennal club 3-segmented, club weakly asymmetrical, antennomere XI not constricted ( Fig. 10b ). Mandible ( Fig. 10a ) with apex bidentate; with retinaculum; mandible without ventral ridge. 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; without or with weakly developed scutellar lobe. 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 (often long) spinelike setae at apex. Protrochanter without setae; protibia without ctenidium on kickface ( Fig. 10c ). Scutellar shield small. Elytron without spectral iridescence; one sutural stria present; discal striae unimpressed, but sometimes represented by rows of faint, round punctures; without transverse strigae; lateral margin with row of tiny, sawtooth-like setae. Mesoventral plate ( Fig. 10f ) notched anteriorly, extending posteriorly to metaventrite, dividing mesoventral disc in two, procoxal rests indistinct or absent; mesanepisternum with incomplete transverse carina; mesocoxal cavities moderately widely separate, separated by less than half width of a coxal cavity. Mesotarsomere III bilobed. Metaventral process ( Fig. 10f ) not extending anteriorly beyond anterior level of mesocoxae; metaventral postcoxal lines diverging from mesocoxal cavity margin, usually angulate behind, often with a spur ( Fig. 10f ), branches occasionally not meeting or inner branch absent, rarely arcuate and smoothly rounded; discrimen short, extending less than halfway to anterior margin of metaventral process, or absent; metendosternite ( Fig. 10g ) 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 absent; metatibial foreface with apical ctenidium roughly perpendicular overall to long axis of tibia; spurs cylindrical, longest spur distinctly shorter than width of tibial apex; metatarsomere I shorter than metatarsomere II, joint between I and II flexible ( Fig. 10d ). Hind wing ( Fig. 10e ) 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 unbranched apically; CuA 2 and MP 3+4 without distal remnants; r4 absent; flecks present in apical field just distal to rp-mp2; short 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; ventrite III with toothed process medially in a few Nearctic forms; spiracles apparently absent from segment VII. Male with aedeagus upright in repose; tegmen ( Fig. 10h ) with symmetrical anterior margin, parameres fused to basal piece, parameres sometimes with medial longitudinal division; penis ( Fig. 10i ) variable, with endophallic spicules, often with large sclerites, apex with weak to strong median projection; spiculum gastrale V-shaped, with arms free. Female ovipositor weakly sclerotized, palpiform.

Immature stages. Larval characters of Stilbus were illustrated and discussed in Steiner (1984) and Lawrence (1991).

Bionomics. Members of this genus are commonly swept from grassy areas. Specific feeding habits are unknown, but they probably are generalist mold feeders, much like members of Acylomus . They are strongly attracted to lights at night.

Distribution and diversity. A cosmopolitan genus, nearly coextensive with the distribution of the family as a whole, but apparently not well represented in the Australian region. This genus has been excellently treated for the Palearctic region ( Švec 1992, including species now placed in Acylomus ) and the Afrotropical region ( Švec 2003), although much work still remains to be done, especially in the latter region. The exceedingly rich New World fauna has yet to receive a needed modern revision.

Included species (71):

Stilbus abbreviatus Casey, 1916 ( Distribution : United States) (type!)

Stilbus aequalis ( Sharp, 1888) (Distribution: Guatemala) (type!)

Stilbus angulatus Champion, 1925 (Distribution: subsaharan Africa) (type!)

Stilbus angulicaput ( Scott, 1922) (Distribution: Seychelles) (type!)

Stilbus angustus Casey, 1916 ( Distribution : United States) (type!)

Stilbus apertus Casey, 1916 ( Distribution : United States) (type!)

Stilbus apicalis (Melsheimer, 1846) (Distribution: Canada, United States) (type!)

Stilbus apicipennis (Brèthes, 1924) , comb. nov. ( Phalacrus ) ( Distribution : Argentina) (type!)

Stilbus aquatilis (LeConte, 1856) (Distribution: United States) (type!)

Stilbus atomarius ( Linné, 1767) (Distribution: Palearctic region)

Stilbus australis ( Brèthes, 1922) , comb. nov. ( Phalacrus ) (Distribution: Argentina)

Stilbus avunculus Flach, 1889 (Distribution: China, Japan)

Stilbus belfragei Casey, 1916 ( Distribution : United States) (type!)

Stilbus bipustulatus Champion, 1925 ( Distribution : Japan) (type!)

Stilbus brevisternus (Guillebeau, 1893) (Distribution: Vietnam) (type!)

Stilbus brunnescens ( Motschulsky, 1858) , comb. nov. ( Olibrus ) (Distribution: Sri Lanka)

Stilbus cinctus (Fauvel, 1903) (Distribution: New Caledonia)

Stilbus compactus Lyubarsky, 2003 (Distribution: Thailand)

Stilbus convergens Casey, 1890 ( Distribution : United States) (type!)

Stilbus coxalis Švec, 1992 (Distribution: Japan)

Stilbus daublebskyorum Švec, 2003 (Distribution: Guinea)

Stilbus dollmani Champion, 1925 ( Distribution :? Zimbabwe) (type!)

Stilbus ferrugineus Švec, 1992 (Distribution: Azerbaijan)

Stilbus fidelis Casey, 1916 ( Distribution : United States) (type!)

Stilbus finitimus Casey, 1916 ( Distribution : United States) (type!)

Stilbus floridanus Casey, 1890 ( Distribution : United States) (type!)

Stilbus galvestonicus Casey, 1916 ( Distribution : United States) (type!)

Stilbus gossypii (Brèthes, 1912) (Distribution: Argentina)

Stilbus guillebeaui Hetschko, 1928 ( Distribution : Indonesia) (type!)

Stilbus japonicus Švec, 1992 (Distribution: Japan)

Stilbus limatus Casey, 1916 ( Distribution : United States) (type!)

Stilbus ludibundus Casey, 1916 ( Distribution : United States) (type!)

Stilbus ludovicianus Casey, 1916 ( Distribution : United States) (type!)

Stilbus merkli Švec, 1992 (Distribution: Russia)

Stilbus misellus (Guillebeau, 1894) (Distribution: Indonesia) (type!)

Stilbus modestus Casey, 1890 ( Distribution : United States) (type!)

Stilbus mollis ( Sharp, 1888) (Distribution: Guatemala) (type!)

Stilbus nanulus Casey, 1890 ( Distribution : United States) (type!)

Stilbus nitidus (Melsheimer, 1846) (Distribution: United States) (type!)

Stilbus notabilis (Fall, 1901) (Distribution: United States) (type!)

Stilbus oblongus ( Erichson, 1845) (Distribution: Palearctic region)

Stilbus obscurus Casey, 1890 ( Distribution : United States) (type!)

Stilbus obtusus (LeConte, 1856) (Distribution: Mexico, United States) (type!)

Stilbus ochraceus Casey, 1916 ( Distribution : United States) (type!)

Stilbus olearis Lyubarsky, 2003 (Distribution: Nepal)

Stilbus orbicularis Lyubarsky, 2003 (Distribution: Nepal)

Stilbus pallidus Casey, 1890 ( Distribution : United States) (type!)

Stilbus pannonicus Franz, 1969 (Distribution: Palearctic region)

Stilbus piceus ( Boheman, 1858) , comb. nov. ( Olibrus ) (Distribution: United States)

Stilbus placidus ( Sharp, 1888) (Distribution: Mexico) (type!)

Stilbus posticalis ( Sharp, 1888) , comb. nov. ( Olibrus ) ( Distribution : Guatemala, Mexico) (type!)

Stilbus probatus Casey, 1916 ( Distribution : United States) (type!)

Stilbus prudens Casey, 1916 ( Distribution : United States) (type!)

Stilbus pubicoxis (Guillebeau, 1893) (Distribution: Vietnam) (type!)

Stilbus pusillus (LeConte, 1856) (Distribution: United States) (type!)

Stilbus seriatus (Guillebeau, 1894) (Distribution:? Brazil) (type!)

Stilbus sharpi (Guillebeau, 1892) (Distribution: Africa, Middle East) (type!)

Stilbus shastanicus Casey, 1916 ( Distribution : United States) (type!)

Stilbus simplex Lyubarsky, 1998 (Distribution: Namibia)

Stilbus sphaericulus Casey, 1916 ( Distribution : United States) (type!)

Stilbus sternosetosus ( Lyubarsky, 1998) (Distribution: Namibia)

Stilbus subalutaceus Casey, 1890 ( Distribution : United States) (type!)

Stilbus sublineatus (Guillebeau, 1894) (Distribution: Haiti) (type!)

Stilbus substriatus (Guillebeau, 1894) (Distribution: Indonesia) (type!)

Stilbus testaceus (Panzer, 1797) (Distribution: Palearctic region)

Stilbus trisetosus Casey, 1916 ( Distribution : United States) (type!)

Stilbus truncatus Švec, 1992 ( Distribution : Morocco) (type!)

Stilbus univestis (Guillebeau, 1894) (Distribution: Cuba) (type!)

Stilbus viduus Casey, 1890 ( Distribution : United States) (type!)

Stilbus yezoensis Hisamatsu, 1985 (Distribution: Japan)

Stilbus zotti Švec, 2003 (Distribution: Guinea)

Discussion. Based on the original description, Olibrus piceus , described from San Francisco, California, USA by Boheman (1858), possesses the characters of Stilbus , in particular the single sutural stria and rows of slight punctures on the elytra. I have tentatively moved it to this genus.

Enough characters were illustrated in Brèthes (1922: Fig. 2 ), including prosternal process apically with stiff setae, metaventral postcoxal lines with a single branch and extending to posterior margin, and hind tarsal structure to move his species Phalacrus australis to Stilbus .

The species decribed as Stilbus libidinosus Lyubarsky, 2003 , cannot belong to this genus. The tegmen has hinged parameres (see Fig. 24 , Lyubarsky 2003). Additionally, this species has arcuate metaventral postcoxal lines (see Fig. 23 in Lyubarsky 2003). I am provisionally transferring this species to Acylomus .

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 10. Stilbus nr. apicalis, male. (a) Right 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 23. Tolyphus (Tolyphus) granulatus, male. (a) Left mandible, dorsal; (b) left antenna (scale bar = 0.5 mm). (c) Left protibia and tarsus, dorsal; (d) right 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 24. Antennogasmus cordatus, 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 = 1.0 mm). (g) Metendosternite (scale bar = 1.0 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.