Stenotarsus exiguus Gorham

Arriaga-Varela, Emmanuel, Zaragoza-Caballero, Santiago, Tomaszewska, Wioletta & Navarrete-Heredia, Jose Luis, 2013, Preliminary review of the genus Stenotarsus Perty (Coleoptera: Endomychidae) from México, Guatemala and Belize, with descriptions of twelve new species, Zootaxa 3645 (1), pp. 1-79 : 12-13

Stenotarsus exiguus Gorham

(Figs. 15, 55, 91, 116, 144, 159, 184, 202–203, 246, 258)

Stenotarsus exiguus Gorham, 1890: 141 . Blackwelder 1945: 439; Strohecker 1953: 52; Shockley et al. 2009a: 81.

Diagnosis. This species is easily distinguished by its small size, and homogeneous dark brown coloration (Fig. 15), the metatrochanters lobed distally, metafemur with very long setae (almost half length of metafemur), and metatibia stout, clearly sinuate in males ( Fig. 159 ), less sinuate in females ( Fig. 184 ).

Description of males. Body 3.40–3.92 mm long, distinctly small, short oval, moderately convex (Fig. 15), 1.66–1.75X as long as wide, 2.83–3.00X as long as high. Uniformly dark brown, except antennomeres 8–11, which are black. Moderately densely covered with rather long, suberect, golden setae.

Head: Clypeus transverse, 2.0X wider than long. Terminal labial palpomere narrow, acuminate, narrowly truncate apically. Interocular distance 0.62–0.68X as wide as head. Antenna rather short and slender ( Fig. 55 ), 0.37X as long as body; scape 1.5X as long as wide, 1.5X longer than pedicel; pedicel 0.1X longer than wide; third antennomere 1.5X as long as wide, 0.9X as long as pedicel; fourth to seventh subequal to third; eighth as long as wide, as long as pedicel; antennal club 0.45X as long as total antennal length, with segments almost symmetrical; ninth antennomere widening apically, 1.1X as long as wide, 1.7X as long as pedicel; tenth widening apically, as long as wide, 1.8X as long as pedicel; terminal antennomere subrectangular, 1.5X as long as wide, 3X as long as pedicel.

Prothorax: Pronotum ( Fig. 91 ) widest at base, transverse, 2.0–2.1X wider than long; 1.78–1.84X wider at base than at front angles; 2.07–2.20X wider than head. Sides weakly convergent in basal half then rounded to front angles. Front angles produced, right-angled, slightly rounded at tip. Hind angles weakly acute. Anterior margin narrow, arcuate medially. Lateral margins raised, wide, narrowing posteriorly in basal half; width of margin at base 1/4 of the distance between basal pore and hind angle; area between marginal line and pronotal edge flat. Disc moderately convex, finely and moderately closely punctate; lateral sulci rather deep, short, slightly convergent. Basal pores small, somewhat elongate. Basal sulcus absent medially. Pronotal base slightly lobed medially. Prosternal process narrow at base, slightly widened posteriorly, slightly narrower than longitudinal procoxal diameter apically.

Pterothorax: Scutellum triangular, small, 1.35–1.45X wider than long, 0.13X as wide as pronotum. Elytra length 2.25–2.60 mm; 1.09–1.16X longer than wide; 2.93–3.20X longer and 1.30X wider than pronotum; ovoid, widest at basal third, then roundly convergent to moderately acuminate apex. Moderately densely punctate with foveolate punctures moderately large and deep, separated by 1.5–4.0 diameters ( Fig. 116 ), sparser and shallower near elytral apex and near scutellum. Humerus rather prominent. Epipleuron at base 0.85X as wide as intercoxal process of metaventrite. Mesoventrite deeply excavated in front; bearing small setose pore laterally, near anterior margin; mesoventral process slightly wider than longitudinal coxal diameter, lacking medial carinae. Metaventrite moderately convex, without modifications on anterior margin; with pair of small setose pores posterior to each mesocoxa. Metepisternum with small setose pore.

Legs: short, distinctly stout ( Figs. 144 , 159 ). Trochanters unarmed, metatrochanter with posterior margin lobed distally. Meso and metafemora moderately widened at midlength, unarmed, metafemur as long as mesofemur, bearing distinctly long setae, 0.3–0.5X as long as femur. Meso- and metatibiae markedly stout; metatibia scarcely shorter than metafemur, 0.29–0.32X as long as elytra, weakly widening apically, sinuate, unarmed. Metatarsus 0.57–0.62X as long as metatibia; second tarsomere 2.5X wider apically as fourth tarsomere at midlength.

Abdomen: ventrite I slightly shorter than metaventrite and distinctly shorter than ventrites II–V combined, with sparse coarse foveolate punctation, without protuberances. Ventrite V almost twice as long as IV, with apex briefly truncate. Ventrite VI rounded apically. Tergite VIII slightly truncate. Aedeagus with median lobe short and stout, curved, weakly constricted in apical third, in ventral view ( Fig. 203 ); narrowing apically, in lateral view ( Fig. 202 ). Tegmen with tegminal plate moderately large.

Description of females. Body 3.25–3.90 mm long, 1.70–1.75X as long as wide, 2.57–2.60X as long as high. Antenna 0.35–0.37X as long as body. Pronotum 2.13–2.20X wider than long, 1.91–1.95X wider at base than at front angles, 2.25–2.30X wider than head. Elytra 2.1–2.5 mm long, 1.07–1.13X longer than wide, 2.9–3.1X longer and 1.22–1.31X wider than pronotum. Metatrochanter scarcely lobed distally. Metatibia 0.29–0.30X as long as elytra, stout, scarcely sinuate ( Fig. 184 ). Metatarsus 0.6X as long as metatibia. Ovipositor with proctiger acuminate; coxites markedly wide, without styli ( Fig. 246 ).

Sexual dimorphism. Female metatibiae are narrower and less sinuate ( Fig. 184 ).

Variation. No significant variation was found.

Material examined. Types. Lectotype (present designation) (male): Syntype [round, blue bordered label] / San Juan, Vera Paz, Champion / St.exiguus Gorh [h]/ B.C.A., VII, Stenotarsus [p] exiguus Gorh. [h] (NHM); Paralectotype (female): Syntype [round, blue bordered label] / Rio Hondo, Br. Honduras, Blancaneaux / St. exiguus Gorh [h]/ B.C.A., VII, Stenotarsus [p] exiguus Gorh. [h] (NHM).

Other material. 15.4, Cacao, Trece Aguas / Alta V. Paz, Guatemala / Schwarz & Barber coll. / adumbratus dt. Stroh. (1 male: NMNH); 25.4, Cacao, Trece Aguas / Alta V. Paz, Guatemala / Schwarz & Barber coll. / S. sp. (1 female: NMNH); MEXICO: Motzorongo (1 female, 1 male: MNB); [same data except] Stenotarsus sp. indesct, det. H.F. Strohecker (1 male: MNB).

Distribution. BELIZE: Corozal; GUATEMALA: Alta Verapaz; MEXICO: Veracruz ( Fig. 258 ).

Biological Notes. Altitudinal range: 10–1500 m.

Remarks. This species is recorded from México for the first time.

Figures

FIGURES 158 – 173. Hind legs of male Stenotarsus spp. 158) S. cortesi; 159) S. exiguus; 160) S. globosus; 161) S. guatemalae; 162) S. incisus; 163) S. kafkai; 164) S. latipes; 165) S. lemniscatus; 166) S. marginalis; 167) S. mesoamericanus; 168) S. mexicanus; 169) S. militaris; 170) S. molgorae; 171) S. monterrosoi; 172) S. nigricans; 173) S. oblongulus.

FIGURES 174 – 185. 174 – 183. Hind legs of male Stenotarsus spp. 184 – 185. Hind legs of female Stenotarsus spp. 174) S. ovalis; 175) S. parallelicornis; 176) S. raramuri; 177) S. rubrocinctus; 178) S. rulfoi; 179) S. sallaei; 180) S. shockleyi; 181) S. smithi; 182) S. spiropenis; 183) S. thoracicus; 184) S. exiguus; 185) S. globosus.

FIGURES 54 – 71. Right antennae of Stenotarsus spp. 54) S. cortesi; 55) S. exiguus; 56) S. globosus, S. rubrocinctus; 57) S. guatemalae; 58) S. incisus; 59) S. kafkai; 60) S. latipes; 61) S. lemniscatus; 62) S. marginalis; 63) S. mesoamericanus; 64) S. mexicanus; 65) S. militaris; 66) S. molgorae; 67) S. monterrosoi; 68) S. nigricans; 69) S. oblongulus; 70) S. ovalis; 71) S. parallelicornis.

FIGURES 90 – 104. Pronotum of Stenotarsus spp. 90) S. cortesi; 91) S. exiguus; 92) S. globosus; 93) S. guatemalae; 94) S. incisus; 95) S. kafkai; 96) S. latipes, S. molgorae; 97) S. lemniscatus; 98) S. marginalis; 99) S. mesoamericanus; 100) S. mexicanus; 101) S. militaris; 102) S. monterrosoi; 103) S. nigricans; 104) S. oblongulus.

FIGURES 115 – 125. Surface of elytron of Stenotarsus spp. 115) S. cortesi; 116) S. exiguus; 117) S. globosus; 118) S. kafkai; 119) S. lemniscatus; 120) S. ovalis; 121) S. militaris; 122) S. raramuri; 123) S. rulfoi; 124) S. shockleyi; 125) S. spiropenis.

FIGURES 144 – 157. Structure of hind legs of Stenotarsus spp. 144 – 149 Hind leg. 150 – 153. Base of male metafemur. 154 – 157. Metatarsus. 144) S. exiguus; 145) S. globosus; 146) S. latipes; 147) S. nigricans; 148) S. spiropenis; 149) S. ovalis; 150) S. globosus; 151) S. raramuri; 152) S. rubrocinctus; 153) S. shockleyi; 154) S. globosus; 155) S. incisus; 156) S. spiropenis; 157) S. oblongulus.

FIGURES 200 – 223. Lateral and ventral view of median lobe of edeagus of Stenotarsus spp. 200 – 201) S. cortesi; 202 – 203) S. exiguus; 204 – 205) S. globosus, S. raramuri, S. rubrocinctus, S. shockleyi; 206 – 207) S. guatemalae; 208 – 209) S. incisus; 210 – 211) S. kafkai, S. mexicanus; 212 – 213) S. latipes; 214 – 215) S. lemniscatus; 216 – 217) S. marginalis; 218 – 219) S. mesoamericanus; 220 – 221) S. militaris; 222 – 223) S. molgorae.

FIGURES 244 – 256. Female genitalia structures of Stenotarsus spp. 244) Ovipositor with spermatheca and accessory gland of S. spiropenis, dorsal. 245 – 256. terminal part of ovipositor, dorsal. 245) S. cortesi; 246) S. exiguus; 247) S. globosus, S. raramuri, S. rubrocinctus, S. shockleyi; 248) S. incisus; 249) S. latipes; 250) S. mesoamericanus; 251) S. mexicanus; 252) S. monterrosoi; 253. S. nigricans. 254. S. ovalis. 255. S. sallaei. 256. S. thoracicus.

FIGURES 257 – 259. Distributional maps of Stenotarsus spp. 257) S. cortesi (C), S. mesoamericanus (S), S. parallelicornis (T); 258) S. exiguus (C), S. incisus (S); 259) S. globosus (C), S. rubrocinctus (S), S. raramuri. (T). Yellow circles (C), red squares (S), blue triangles.