Arthrobrachus crassicornis sp. nov (Coleoptera: Melyridae), a new species from the South American Transition Zone in Argentina Author Estrada, Patricia text Zootaxa 2024 2024-09-10 5506 4 587 593 http://dx.doi.org/10.11646/zootaxa.5506.4.8 journal article 302906 10.11646/zootaxa.5506.4.8 5eb84b17-1235-4dea-a791-5be8e3076bf7 1175-5326 13747487 7ADD1BE9-B568-40D2-8F11-D5DA1E19DD74 Arthrobrachus crassicornis sp. nov. ( Figures 1–6 ) FIGURE 1: Arthrobrachus crassicornis sp. nov. Scale 1 mm. 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 FIGURE 2: Arthrobrachus crassicornis sp. nov. Antenna ( a ); Pronotum ( b ). Scale 1 mm. FIGURE 3: Arthrobrachus crassicornis sp. nov. Female, abdomen ( a ), v : V ventrite, vi : VI ventrite, and lt : last tergite. Scale 1 mm. Ovipositor, ventral view ( b ), bo : baculi oblique, bv : ventral baculi, vl : ventral lamina; dorsal view ( c ), dl : dorsal lamina, bp : proctiger baculi. Scale 1 mm. 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. FIGURE 4: Arthrobrachus crassicornis sp. nov. Male, abdomen ( a ), v : V ventrite, pa : abdominal process; vi : VI ventrite and lt : last tergite, Scale 1 mm. Segment 9 ( b ). Scale 1 mm. FIGURE 5: Arthrobrachus crassicornis sp. nov. Male genitalia. Tegmen and parameres: dorsal view ( a ), p : parameres; ventral view ( b ); lateral view ( c ) ap : apodeme, Scale 1 mm. Median lobe: dorsal view ( d ), pha : phallotreme; ventral view ( e ); lateral view ( f ), ap : apodeme. Scale 1 mm. FIGURE 6: Distribution map of Arthrobrachus crassicornis sp. nov. (*) in the biogeographic provinces of the South America transition zone (colored in green), acco rding to Morrone et al. (2022) . Description. The body shape is moderately oblong ( Fig. 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 ). 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 , 2a ). 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 ). 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 ); Genitalia: membranous ovipositor; short stylus as long as wide ( Fig. 3 b,c ); ventral baculi longer than the oblique baculi (1.3:1) ( Fig.3b bo , bv ); fine and long proctiger baculi, longer than ventral baculi (1.2:1) ( Fig. 3c 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 ); segment 9 with membranous tergum, thin sternal arms, and narrow apodeme ( Fig. 4b ). 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 ); 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 ). Median lobe subcylindrical, sclerotized, elongate, and moderately curved in basal half with apex slightly elongate ( Fig. 5 d–f ); phallotreme, broad, and acuminate at the base ( Fig. 5 d pha ) with apodeme widening at the base ( Fig. 5 d–f ). 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 ).