Arthrobrachus crassicornis, Estrada, 2024

Arthrobrachus crassicornis sp. nov.

( Figures 1–6 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Type material:

Holotype: male specimen mounted on card with locality data: Argentina, Neuquén, Río Agrio , dic. 1952 ( MLPA).

Paratypes: male specimen mounted on card with locality data: Argentina, Neuquén, Río Agrio, Köhler , Coll. C. Bruch ( MACN) ; female specimen mounted on card with locality data: Argentina, Jujuy, La Quiaca, 02/1947, F. Monrós ( IFML) ; female specimen mounted on card with locality data: Argentina, San Luis, San Gerónimo, 11/1974, Coll. Viana Arg. 025092 ( JEBC) .

Etymology. The name of this species is in New Latin, meaning thick-horned, which refers to its broad and thick antennal segments

Diagnosis.

Head, pronotum and body black with sparse fine hairs; pronotum with sparse long light hairs, elytra light or dark testaceous. The sixth to tenth antennomeres thick. The pronotum with complete oblique lateral carina. In females, the ovipositor is membranous with a small stylus. In males, the parameres are fused and convergent-sided towards the apex, at an oblique angle to the tegmen. The tegminal plate is broad and elevated at the midline. The medial lobe is curved towards the base and sub-rectal at the apex.

Description.

The body shape is moderately oblong ( Fig. 1 View FIGURE 1 ); body length average 4.9 mm (range: 4.8–5.0, n=4); longer than wide (1.8:1) subparallel sides, slightly convex ( Fig.1 View FIGURE 1 ). Head, pronotum and elytra are densely punctured and covered in fine, short pubescence; pronotum with sparse fine, long, light hairs; head, pronotum and venter black, elytra either light or dark testaceous; antennae and legs orange.

Head. Including eyes slightly narrower than the pronotum (0.95:1 ratio); antennae shorter than pronotum (0.36:1ratio), with antennomeres sixth to tenth dilated and thickened ( Figs.1 View FIGURE 1 , 2a View FIGURE 2 ).

Thorax. Pronotum wider than long with a transverse shape (1.5:1 ratio); slightly convex transversely being widest at the base; basal margin is narrower than the humeral region (0.43:1); distal, lateral, and basal margins are moderately marked; the oblique lateral carina extends from the anterior margin to the basal angle of pronotum ( Fig. 2b View FIGURE 2 ). Elytra elongated, lateral margins subparallel in the basal two thirds, then convex in the distal one; slightly convex disk. Legs: tibiae with scarce and small spines at the external margin, tarsomeres with few ventral spines.

Abdomen: females: ventrite 5 with distal margin sinuate at middle, spiculum ventral fine and curved, longer than ventrite 5 (1.3:1); ventrite 6 a transverse plate, distal margin projected and moderately emarginated at the center; last tergite moderately elongated, distal margin projecting and emarginate to the center ( Fig. 3a View FIGURE 3 ); Genitalia: membranous ovipositor; short stylus as long as wide ( Fig. 3 b,c View FIGURE 3 ); ventral baculi longer than the oblique baculi (1.3:1) ( Fig.3b View FIGURE 3 bo, bv); fine and long proctiger baculi, longer than ventral baculi (1.2:1) ( Fig. 3c View FIGURE 3 bp); ventral and dorsal laminae with short and scarce pubescence.

Males: ventrite 6 two transversal, sub-contiguous plates; last tergite with distal margin convex and distal angles rounded ( Fig. 4a View FIGURE 4 ); segment 9 with membranous tergum, thin sternal arms, and narrow apodeme ( Fig. 4b View FIGURE 4 ). Genitalia: Parameres fused and sclerotized, sides converging towards the apex and fused ventrally, slightly curved at an obtuse angle to the tegmen ( Fig. 5 a–c View FIGURE 5 ); tegmen with a marked dorsal ridge at the base of parameres, moderately thin; laterally convex tegminal arms converging towards the base, broad sclerotized tegminal plate, raised in the midline, its apodeme dorsal and laminate ( Fig. 5 a–c View FIGURE 5 ). Median lobe subcylindrical, sclerotized, elongate, and moderately curved in basal half with apex slightly elongate ( Fig. 5 d–f View FIGURE 5 ); phallotreme, broad, and acuminate at the base ( Fig. 5 d View FIGURE 5 pha) with apodeme widening at the base ( Fig. 5 d–f View FIGURE 5 ).

Distribution. ARGENTINA, Jujuy Province, La Quiaca (IMFL) 1♀; San Luis Province, San Gerónimo 1♀ (JEBC); Neuquén Province, Río Agrio (MLPA) 1♂, Río Agrio (MACN) 1♂.

Remarks

According to the collection data reviewed in this study, the geographic distribution of Arthrobrachus crassicornis sp. nov. corresponds to the Puna Province, Monte Province, and Comechingones Province of the South American transition zone ( Morrone et al. 2022) ( Fig. 6 View FIGURE 6 ).