Smicridea (Rhyacophylax) atrobasis Flint, 1983

Figs 1D, 6A-D

Smicridea (Rhyacophylax) atrobasis Flint, 1983: 63. Paprocki et al. 2004: 9 [checklist]. Sganga 2006: 142 [distribution]. Sganga and Angrisano 2005: 132 [distribution]. Rueda Martín and Sganga 2011: 2225 [♂; distribution]. Paprocki and França 2014: 32 [checklist]. Isa Miranda and Rueda Martín 2014: 200 [distribution]. Holzenthal and Calor 2017: 163 [catalog].

Material examined.

Uruguay • 22 males; Salto, Salto Grande; 19 Nov. 1955 ; a la luz, en la cascada; FHCM • 1 male; Artigas, río Uruguay, barra Arroyo Guaviyu; 22 Nov. 1954; CS Carbonell leg. (OS Flint Jr. det.) • 1 male; San Gregorio; 29 Nov. 1959; Carbonell, Mesa, San Martín leg. (OS Flint Jr. det.) .

Description.

Adult male. Coloration of the body in alcohol stramineous. Length of forewings 5.4 mm (n = 18). We were not able to observe the coloration of the wings in the specimens preserved in alcohol due to discoloration of the cuticle through time, but Flint (1983) described it from dried specimens as follows: "forewings dark purplish black in basal quarter and in two transverse bands apicad, otherwise covered with golden hair".

Head (Fig. 1D). In dorsal view rectangular, transverse. Mesal margins of the eyes, in dorsal view, convex, postgenal areas reduced. Interocular area rectangular, narrow, longer than wide. Interocular distance 7.3 × shorter than MHW. Coronal suture 2.2 × longer than IOD. Eyes very prominent, maximum eye width 2.4 × shorter than MHW. Anterolateral setose warts present, elongate, oval. Posterior setose warts subtriangular. Maxillary palp formula: I, II-III, IV-V.

Male genitalia. Anterolateral margin of segment IX sinuous. Tergum of segment X triangular in lateral view, dorsal and ventral margins rounded, with a ventral sclerotized Y-shaped area directed anteriorly through segment IX (Fig. 6A); in dorsal view divided mesally into two triangular hemitergites, with apex pointed, mesal margins concave (Fig. 6B). Inferior appendages with two articules, basal article slightly widened distally, apical one curved mesad in dorsal view, apex pointed (Fig. 6A, B). Phallus long, with a tubular phallobase; basal portion broad, forming an angle of ~ 120° with distal part; apex broadened, ending in two laterodorsal and two lateroventral lobes, that become directed basad as the endotheca is everted (Fig. 6A, C, D). Internal sclerotized section of ejaculatory duct ~ 2/3 the phallobase length, straight, slightly upturned apically in lateral view (Fig. 6A, C); in dorsal view longitudinally divided in two, apex shaped like an arrowhead (Fig. 6D). Endotheca simple.

Systematic considerations.

This species seems to be closely related to Smicridea mesembrina . These two species bear apicolateral lobes on the phallus, but while the apex of the sclerotized section of the ejaculatory duct in S. mesembrina is simple, in S. atrobasis it is shaped like an arrowhead. Additionally, S. atrobasis has a very distinctive feature that is the prominent eyes and reduced interocular area.

Distribution.

Argentina, Bolivia, Brazil, Uruguay.