Thyreocephalus scutellaris ( Sharp, 1885 )

Márquez, Juan & Asiain, Julieta, 2016, Taxonomy of the Mexican species of Thyreocephalus Guérin-Méneville (Coleoptera: Staphylinidae, Xantholinini), Zootaxa 4169 (2), pp. 251-285 : 262-263

Thyreocephalus scutellaris ( Sharp, 1885)

( Figs. 2 c, d, 5d, 6e, 9d, 11d, 13a)

Saurohypnus scutellaris Sharp, 1885: 502 .

Thyreocephalus scutellaris Smetana, 1977: 348

Total body length 10.8–13.9 mm. Body black, except elytra, almost posterior half of fifth visible abdominal segment, all sixth and genital segment reddish; antennomeres 3–11, maxillary and labial palps, and tarsi reddish brown.

Head subrectangular, with lateral margins almost parallel, 1.25 times longer than wide and 1.13 times wider than pronotum ( Fig. 2 c). Dorsal surface moderately convex, with umbilicate punctures moderately dense, punctures separated by three times or more their width, almost homogeneously distributed, although sparse on the front (area between frontal sutures) and toward lateral and posterior borders ( Fig. 2 c). Several fine punctures also are present. Ventral surface with fine and umbilicate punctures as on the dorsal surface, distributed almost homogeneously ( Fig. 2 d). Eye as long as 0.25 times the cephalic length. First antennomere 1.65 times as long as next two combined, third antennomere 1.25 times longer than second, fourth almost quadrate, 5–10 slightly transverse. Labrum with two pairs of apical teeth, lateral pair most acute and central pair quadrate and wide ( Fig. 5 d). Mandibles 0.55 times as long as the cephalic length, left mandible with basal tooth not visible, right mandible with only one tooth. Neck with a small sunken area with pyramidal to triangular shape ( Fig. 2 c).

Pronotum 1.17 times wider at anterior corners than at posterior corners. Scutellum black, with six fine punctures and microsculpture as wavy lines. Elytra almost as long as pronotum, with dense punctures almost homogeneously distributed, except for a smooth belt parallel to lateral margin.

Prosternal sclerite divided longitudinally by a fine midline. Prosternum reddish at anterior third and remainder black; posteromedian carina reduced to a short impressed line that is united to the intercoxal process ( Fig. 6 e). Mesosternum with central carina and rugose microsculpture. Metasternum with pale and long setae as dense as on abdomen.

Abdomen densely setose. First four visible abdominal tergites with a sunken area slightly deep parallel to anterior border. Aedeagus small, length 0.85 mm; base of median lobe oval; apical area of median lobe 0.25 times the total length; parameres symmetrical, longer (0.40 times as long as median lobe); internal sac few visible, slender and short ( Figs. 9 d, 11d).

Variation. In addition to the variation in the total body length, the reddish color on the fifth visible abdominal segment can be more or less than the apical half. The paler coloration of the last three visible abdominal segments can be orange, reddish or brown. Legs (except tarsi) and antennomeres 2 and 3 can be brown to reddish brown. The density of punctures on the dorsal and ventral surface of the head can be slightly variable. The proportion length/ width of the head can be from 1.21 to 1.30 times, and the cephalic width respect to the pronotum width from 1.06 to 1.33 times. The fine punctures on the scutellum varies from 5–7 punctures, but commonly there are six punctures. The aedeagus length varies from 0.85 to 0.95 mm.

Diagnosis. This species is distinguished from the remaining Mexican species by relatively small body size, the small and pyramidal shaped of the sunken area on the neck, the reddish color of the last two visible abdominal segments and apical half of the fifth, as well as the size and form of the aedeagus.

Discussion. Casey (1906) described Saurohypnus dugesi apparently based on just one specimen, he commented: "This species, sent me many years ago, appears to differ from scutellaris , the type of the genus, in having the tip of the abdomen red and in its somewhat smaller size. The scutellum has five or six coarse close-set punctures as in scutellaris ". Later Smetana (1977) transferred the species to Thyreocephalus . However, after the examination and comparison of the lectotype of T. scutellaris with remaining specimens (17 from four Mexican states), all identified as T. dugesi by us and by J. L. Navarrete-Heredia (according to the labels), we do not find specific differences of the morphological variation included previously (body size and color). Moreover, dissections revealed that the aedeagus was the same in the lectotype and the remaining dissected specimens. Unfortunately, we do not have an opportunity to study the type of T. dugesi to propose it as a junior synonym of T. scutellaris with certainty. As we are unable to distinguish T. scutellaris from T. dugesi , and with the possibility that the last one can be synonymous with the first one, we do not include taxonomic information for T. dugesi in this work.

Distribution ( Fig. 13 a). Thyreocephalus scutellaris is recorded from Mexico in the states of Chihuahua, Hidalgo, Jalisco, Morelos and Zacatecas ( Table 2 ) ( Sharp 1885, Navarrete-Heredia et al. 2002).

Type material examined of T. scutellaris . Lectotype (male): “ Saurohypnus scutellaris Type D.S. Pinos Altos, Chihuahua . B. Hepburn (on the cardboard plate with the specimens) / Type / Pinos Altos, Chihuahua, Mexico. Buchanan- Hepburn./ B.C.A.Col. 1.2. Saurohypnus scutellaris Sharp. / Sharp Coll. 1905,- 313./ LECTOTYPE Saurohypnus scutellaris Sharp, A. Smetana des. 1977/ Thyreocephalus scutellaris Shp. Smetana det. 1977” ( BMNH).

Additional material examined. “Mexico: Hidalgo, Tepehuacán de Guerrero, Chilijapa , N 21°01.2’ 5.1” , W 98°51.8’ 2,1”, bosque mesófilo de montaña, 1401 m, trampa de intercepción de vuelo #1, 11 a 25-III-2011, J. Márquez col.” (1♂, 1♀, CC-UAEH); " Mexico : Jalisco, Tequila, Volcán de Tequila , bosque mesófilo de montaña, 2350 m, 30-IV-1994, ex hojarasca, H. Fierros col.” (1♂, CZUG) ; “Mexico: Jalisco, Tala, Ahuisculco , 1350 m, bosque tropical caducifolio perturbado, 10-VII a 7-VIII-1996, NTP-80, G. A. Quirozy J. L. Navarrete cols.” (1♀, CZUG) ; “Mexico: Jalisco, Talpa de Allende, La Cumbre , N 20°12’54.76” , W104°45’19.20”, bosque de maple, 1750 m, en tronco, 20-II-2015, M. Vásquez-Bolaños col.” (1♂, CZUG); “ Mexico : Morelos, Tlayacapan , San José de los Laureles , bosque mesófilo de montaña, 1860 m, en hojarasca, 28-V-2000, J. Márquez y J. Asiain cols.” (1♂, CC-UAEH) ; same data as previous, except: “bajo roca de riachuelo, 1-IX-1996, J. Márquez col.” (3♂, MZFC) ; same data as previous, except; “ 1800 m, bosque de pino-encino, zonas 4-5,bajo roca, 1-III-1997, J. Márquez col." (1♀; CC-UAEH) ; same data as previous, except: “ 27-X-1990, col. J. L.Navarrete y G. A. Quiroz / ex ribera del rio #659/ Thyreocephalus dugesi (Csy.) J. L. Navarrete det. 2004” (1♀, JLNH) ; “ Morelos: Tlayacapan, Cerro Tlatoani, 24-XI-1991, bosque tropical caducifolio, bajo roca, J. L. Navarrete y G. A. Quiroz, # 1210” (1♀, JLNH) ; “ Zacatecas: Mezquital del Oro, km 9.38 Mezquital-Malacate , 21°09’01.1” N, 103°25’12.1” W, bosque de sabino, 1326 m, 15-II-2004, V. H. Gómez / Thyreocephalus dugesi (Csy.) J. L. Navarrete det. 2004” (1♀, JLNH) .

Figures

FIGURE 2. Thyreocephalus jalapaensis: a) dorsal view of the head and pronotum; b) ventral view of the head (mandibles excluded). Thyreocephalus scutellaris: c) dorsal view of the head and pronotum; d) ventral view of the head (mandibles excluded). Thyreocephalus cribripennis: e) dorsal view of the head and pronotum; f) ventral view of the head (mandibles excluded). Scale = 2 mm.

FIGURE 5. Dorsal view of the labrum of: a) Thyreocephalus unicolor, b) T. sp. aff. subtilis, c) T. jalapaensis, d) T. scutellaris, e) T. puncticeps, g) T. rufipennis, h) T. halffteri, i) T. arizonicus.

FIGURE 6. Ventral view of the pronotum showing the posteromedian carina (lacking in b) and the postcoxal process in: a) Thyreocephalus puncticeps, b) T. sp. aff. subtilis. Lateral view of the pronotum showing the develop and variation of the posteromedian carina in: c) T. puncticeps, d) T. arizonicus, e) T. scutellaris, f) T. jalapaensis, g) T. unicolor.

FIGURE 9. Ventral view of the aedeagus of: a) Thyreocephalus unicolor, b) T. sp. aff. subtilis, c) T. jalapaensis, d) T. scutellaris, e) T. cribripennis, f) T. rufipennis, g) T. halffteri. Scale = 0.5 mm.

FIGURE 13. Geographic distribution and individual track of: a) T. sp. aff. subtilis (black square) and T. scutellaris (gray circles); b) T. cribripennis (black circle) and T. halffteri (gray squares).