Astylus scalaris Pic, 1919b

Estrada, Patricia, 2021, Updating the knowledge of species of the genus Astylus Laporte (Coleoptera Melyridae) from South America, Zootaxa 4941 (1), pp. 127-141 : 134-137

Astylus scalaris Pic, 1919b

( Figures 7–9)

Astylus scalaris Pic, 1919b: 9 ; Pic 1929:12; Blackwelder 1945:379; Estrada 2008:601. (Type locality: Santiago del Estero, Río dulce).

Astylus binotatus Pic, 1940:12 . (Type locality: Nova teutonia). n.syn

Types examined: scalaris : one male herein designated as lectotype and labelled as follows: scalaris Pic. ; octobre; Rpubl. Argentine, Chaco de Santiago del Estero Río Dulce; Type. (MNHN). binotatus : one male herein designated as lectotype and labelled as follows: Astylus binotatus n. sp.; Brasilien Nova Teutonia 2711’ B. 5223’L. Fritz Plaumann; N290 ex Bruch; Type. (MNHN). n.syn

Diagnosis. Head and pronotum black with abundant erect pilosity ( Fig.7); antennae are moderately serrated ( Fig. 8a ); pronotum wider in the middle; abundant coarse and wide punctuation; males: ventrites 2–5 are emarginated at the middle of the distal margin, emargination increasing in amplitude towards ventrite 5; ventrite 6 and the last tergite are fused like a subconical structure; ventrite 6 is strongly emarginated at the distal margin, with two lateral projections ( Fig. 8b ); the last tergite is rounded at the apex ( Fig. 8b ); sclerotized parameres, sides subparallel, apex truncate, slightly emarginated in the middle ( Fig. 9a,b ); tegminal arms are moderately thick and curved at the sides; the tegmen plate is broad with a dorsal elevated fold at the midline ( Fig. 9c ); the median lobe is subcylindrical, elongated, sclerotized with sides convergent towards the apex, and a wide, subapical phallotreme; ventral fold at the base adjacent to apodeme ( Fig. 9 d–f).

Description: Male: average body length 6.3 mm (range: 6–7, n= 6; only males); length: width ratio 3:1, sides sub-parallel; moderately abundant thick erect black hairs on the dorsal surface; pronotum black with abundant coarse and wide punctures; elytra with dense coarse punctuation and abundant erect dark hairs; elytral disc orange or light testaceous with four complete longitudinal black bands or reduced to two bands, one in the middle and one at the apex, varying to completely black with two orange spots on the disc; antennae and legs dark testaceous or black.

Head: Including the eyes, slightly wider than distal margin of pronotum (1.1:1); front slightly depressed between the eyes; frontoclypeal region slightly prolonged and narrowed toward the apex; antennae longer than the length of the pronotum (1.7:1); antennomeres moderately serrated ( Fig. 8a ).

Thorax: Pronotum moderately wider than long (1.3:1), moderately convex transversely, widest at the middle; distal, lateral, and basal margins well marked, with a dot depression adjacent to basal angle, sides flattened, basal margin narrower than humeral region (0.6:1). Elytra longer than wide (4:1), with a moderately marked humeral angle; sides are subparallel and slightly rounded towards the apex; disc is slightly convex, with a slight subapical angle; narrow, pilose and grainy epipleura, sides converging at the apex. Legs: elongated, slender, with moderately abundant bristles in the external margin of the tibiae; tarsomeres with fine ventral spines; fore- and mid-legs with tarsomeres as wide as they are long; hind legs with elongated tarsomeres; toothed claws.

Abdomen: Ventrites 2–5 emarginated medially at the distal margin, and increasing the amplitude of the emargination towards ventrite 5; ventrite 6 and last tergite are fused like a subconical structure; ventrite 6 is strongly emarginated at the distal margin with two lateral blunt projections; last tergite has a narrow projection at the apex ( Fig. 8b ); segment 9 has a membranous tergum in the middle and is sclerotized at the sides; wide and curved sternal arms, with a moderately wide and short apodeme ( Fig. 8c ). Genitalia: sclerotized parameres, sides subparallel, apex truncate, slightly emarginated in the middle, lateral edges are curved ventrally and fused near to the base, moderately emarginated at the base ( Fig. 9a,b ); tegminal arms moderately thick and wide, curved at the sides distally and convergent towards the base; tegminal plate broad with a dorsal elevated fold at the midline, strongly concave at the distal margin; wide and securiform apodeme, consisting of two parallel laminae ( Fig. 9c ). Median lobe subcylindrical, elongated, and sclerotized with sides convergent distally; pointed apex; phallotreme subapical, large, oval; from a lateral view, basal fold with apodeme; large apodeme ( Fig. 9 d–f).

Distribution. ARGENTINA, Santiago del Estero Province: Río dulce (MNHN) 1♁. Chaco Province: Resis- tencia (JEBC) 1♁. Cordoba Province: Calamuchita, El Sauce (JEBC) 1♁. Mendoza Province: Lavalle Telteca (IA- DIZA) 1♁. BRASIL: Enemsillada (IFML) 1♁, Santa Catarina Province: Nova Teutonia (MNHN) 1♁.

According to the collection data of the material reviewed in this study, the geographic distribution of Astylus scalaris corresponds to the Chacoan and Pampean Provinces in the Chacoan dominion and the Atlantic Province in the Parana dominion of the Neotropical region, and to the Monte Province of the South American Transitional Zone in the Andean region ( Morrone 2014, 2018).

Figures

FIGURE 8. Astylus scalaris Pic, 1919b. Male, a: antenna; Terminal segments of abdomen: b: v: V ventrite, vi: VI ventrite and lt: last tergite; c: segment 9. Scale 1 mm.

FIGURE 9. Astylus scalaris Pic, 1919b. Male genitalia. Tegmen and parameres: a: dorsal view; p: parameres; b: ventral view; c: lateral view, ap: apodeme, Scale 1mm. Median lobe: d: dorsal view, pha: phallotreme; e: ventral view; f: lateral view. Scale 1 mm.