Litostilbus Guillebeau, 1894

Gimmel, Matthew L., 2013, <strong> Genus-level revision of the family Phalacridae (Coleoptera: Cucujoidea) </ strong>, Zootaxa 3605 (1), pp. 1-147 : 46-47

8. Litostilbus Guillebeau, 1894

( Figs. 3f ; 12 ; 38g –i )

Litostilbus Guillebeau 1894 a: 283 . Type species: Sphaeridium testaceum Fabricius 1792 , fixed by original designation. Pseudolitochrus Liubarsky 1993 a: 16 . Type species: Phalacrus festivus Motschulsky 1858 , fixed by original designation. Syn.

nov.

Type material. Sphaeridium testaceum Fabricius : three specimens associated with handwritten label “testaceum,” one here designated lectotype to stabilize the species and generic name, sex unknown, right elytron missing, previous (unpublished) lectotype label turned upside down, label added “ LECTOTYPE \ Sphaeridium \ testaceum Fabricius \ des. M.L. Gimmel 2010 [red label]” ( ZMUC), straight pinned. Two paralectotypes, identified as Hydrophilidae and Cerylonidae by Warren E. Steiner, Jr., each with label “ PARALECTOTYPE \ Sphaeridium \ testaceum Fabricius \ det. M.L. Gimmel 2010 [yellow label]” ( ZMUC). All specimens are from “Americae meridionalis Insulis” (= Saint Thomas, Virgin Islands) and collected by “Dom. Smidt” according to original description.

Phalacrus festivus Motschulsky : holotype, sex unknown, “ Phalacrus \ festivus \ Motsch. \ Ind. or. [handwritten, yellow label] // Pseudolitochrus \ festivus Mots. \ det. Lyubarsky 1993 // Holotype \ Phalacrus \ festivus Mots. \ det. Lyubarsky ” ( ZMUM), card mounted.

Diagnosis. Recognized by the large scutellar shield, elytron with one to three striae and spectral iridescence, presence of a protibial ctenidium, mesocoxal cavities not contiguous, and metatarsomere I longer than II.

Description. Small to large, total length 1.8–3.3 mm. Dorsal color testaceous to piceous, New World forms sometimes nebulously bicolored, a few southeast Asian forms strikingly so ( Fig. 38g –i ). Tibial spur formula 2-2-2, tarsal formula 5-5- 5 in both sexes.

Head. Not constricted behind eyes. Eyes medium-sized; facets convex; interfacetal setae absent; weakly emarginate medially; without posterior emargination; periocular groove absent; with transverse setose groove ventrally behind eye. Frontoclypeus not or barely emarginate above antennal insertion; clypeal apex arcuatetruncate. Antennal club 3-segmented, club symmetrical; antennomere XI weakly turbinate ( Fig. 12b ). Mandible ( Fig. 12a ) with apex tridentate; retinaculum absent; mandible without ventral ridge. Maxillary palpomere IV fusiform, elongate, nearly symmetrical; galea short, rounded; lacinia with two stout spines. Mentum with sides divergent toward apex; labial palpomere III fusiform. Labrum with apical margin arcuate. Gular sutures short, barely evident .

Thorax. Pronotum with microsetae present, distinct; with scutellar lobe absent or weakly developed. Prosternum anteriorly with continuous row of marginal setae, setae normal; procoxal cavity with anterolateral notchlike extension; prosternal process angulate in lateral view, conspicuously setose preapically, without row of spinelike setae at apex. Protrochanter without setae; protibia with ctenidium on kickface, extending from about one-half to three-quarters length of tibia ( Fig. 12c ). Scutellar shield large, width at base greater than length of eye. Elytron with spectral iridescence; with two or three sutural striae, rarely with one; disc with rudimentary striae or rows of punctures; with moderate to strong transverse strigae; lateral margin with row of tiny, sawtooth-like setae. Mesoventral plate ( Fig. 12f ) notched anteriorly, not extending posteriorly to metaventrite, forming procoxal rests; mesoventrite sunken medially, not setose; mesanepisternum with complete transverse carina; mesocoxal cavities separated by slightly less than half width of a coxal cavity. Mesotarsomere III not bilobed. Metaventral process ( Fig. 12f ) not extending to anterior level of mesocoxae; metaventral postcoxal lines not separated from mesocoxal cavity margin; discrimen long, extending about halfway to anterior margin of metaventral process; metendosternite ( Fig. 12g ) with anterior tendons moderately separated, ventral process intersecting ventral longitudinal flange at anterior margin. Anterior margin of metacoxa with emargination sublaterally; metacoxal plate with transverse line; metatibial foreface with apical ctenidium roughly perpendicular overall to long axis of tibia; spurs cylindrical, longest spur subequal to or distinctly longer than width of tibial apex; metatarsomere I longer than metatarsomere II, joint between I and II rigid ( Fig. 12d ). Hind wing ( Fig. 12e ) with distinct, ovate anal lobe; leading edge with incomplete row of long setae at level of RA +ScP; AA 3+4 extremely weak, crossvein to Cu absent; cubitoanal system unbranched apically, but curving distally; CuA 2 and MP 3+4 with distal remnants; r4 absent; flecks absent from apical field distal to rp-mp2; long transverse proximal sclerite and faint triangular sclerite present just distal to end of radial bar.

Abdomen. Abdominal ventrite I without paired lines or calli; spiracles present and apparently functional on segment VII. Male with aedeagus upright in repose; tegmen ( Fig. 12h ) with asymmetrical anterior margin and parameres hinged to basal piece, parameres without medial longitudinal division; penis ( Fig. 12i ) long, slender, with small paired sclerites, apex bilobed; spiculum gastrale V- or U-shaped, arms connected by broad sclerotized lamina. Female ovipositor weakly sclerotized, palpiform ( Fig. 3f ).

Immature stages. Unknown.

Bionomics. These beetles have been taken by beating, in Malaise traps, and at lights. One long series from the Bahamas was collected from the trunk of Coccoloba diversifolia Jacq. (Polygonaceae) at night.

Distribution and diversity. Two described species from the West Indies and south Florida (probably synonymous), at least one undescribed species from Central and South America, and three described species from southeast Asia. The stunningly marked southeast Asian forms, like their New World counterparts, seem to show a high degree of intraspecific variation in both size and coloration, and the actual number of species will not be known until a careful taxonomic revision of this genus is undertaken.

Included species (5):

Litostilbus borneensis (Lyubarsky, 1994) , comb. nov. ( Pseudolitochrus ) (Distribution: Indonesia)

Litostilbus festivus ( Motschulsky, 1858) , comb. nov. ( Pseudolitochrus ) (Distribution: southeast Asia) (type!)

Litostilbus malayanus (Champion, 1925) , comb. nov. ( Pseudolitochrus ) ( Distribution : Indonesia, Philippines) (type!)

Litostilbus testaceus (Fabricius, 1792) (Distribution: West Indies) (type!)

Litostilbus tristriatus (Casey, 1890) , comb. nov. ( Ochrolitus ) ( Distribution : USA (Florida )) (type!)

Discussion. While Liubarsky (1993 a) was correct in separating Motschulsky’s Phalacrus festivus from other Old World species by erecting a new genus for it (and later [ Lyubarsky 1994 b] two other species), he did not compare his genus to any New World forms. The New World Litostilbus are structurally almost identical to the southeast Asian Pseudolitochrus , and I have reflected this by synonymizing the two names. Casey’s Ochrolitus tristriatus also belongs here, and may be synonymous with the Fabricius species.

Figures

FIGURE 3. Key characters for Phalacridae. (a) Prosternal process of Acylomus aciculatus Sharp (scale bar = 0.5 mm). (b) First abdominal ventrite of Malagophytus steineri Gimmel. Ovipositor of (c) Phalacrus sp.; (d) Phalacropsis dispar (LeConte); (e) Olibrus aeneus (Fabricius); (f) Litostilbus testaceus (Fabricius) (scale bars = 0.5 mm).

FIGURE 12. Litostilbus testaceus, 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.