Arthrobrachus arquatus Estrada 2018, n. sp.
Creators: name: Estrada, Patricia
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Melyridae
Arthrobrachus
Arthrobrachus arquatus

description: Arthrobrachus arquatus n. sp.
(Figures 1–3)
Specimens examined: Holotype: San Juan, Iglesias. 7625. MACN. Arthrobrachus arquatus Estrada, 2018. Holotype deposited in MACN, ♂. (Specimen without date and collector name.)
Paratypes: San Juan, Iglesias. 7625. MACN. Arthrobrachus arquatus Estrada, 2018. Paratype. Deposited in MACN, 5 ♂ and 5 ♀. San Juan, Iglesias. 7625. Astylus varians Sol. Mus. Nac. Hist. Natural Buenos Aires. Arthrobrachus arquatus Estrada, 2018. Paratype. Deposited in MACN, 1 ♂. (All specimen without date and collector name.)
Etymology. This species is named arquatus (a masculine adjective), refering to the strong anterior-posterior curvature of the body.
Diagnosis. Body very convex longitudinally and transversely. Male with anterior projection of pronotum covering head (Fig. 1a), color reddish or light testaceus and dense reddish pubescence; metasternum grooved medially with two basal, divergent processes with brush-like short rows of setae; ventrite VI with two lateral, flat, transverse, subcontiguous plates (Fig. 2b); last tergite subtriangular, with subacuminate distal margin (Fig. 2b); parameres sub-cylindrical, rounded apically, sides convergent, convex and fused ventrally; median lobe subcylindrical, strongly curved, phallotreme grooved (Fig. 2f, i). Female pronotum with small anterior projection and black with clear edges, dense, dark pubescence (Fig. 1b).
Description. Male: Average body length 6.14 (range: 6.0–7.0 mm, n=7), body reddish or light testaceus, oblong, very convex, length: width ratio 1,7:1. Pronotum black, reddish or light testaceus with dense pubescence, reddish, fine, short and inclined; elytra dark, reddish or light brown with short, erect, dense and sparse hairs (Fig. 1a).
Head. Black; including eyes as wide as the anterior margin of pronotum (0.98:1); dense coarse punctuation at the vertex; antennae shorter than the pronotum (0.35:1), with five medially dilated preapical antennomeres (Fig. 2a) and densely pubescent on inner side.
Thorax. Pronotum as wide as long (1.02:1), strongly convex transversely and moderately convex longitudinally, base wider than apex (1.85:1) and as wide as humeral region (0.97:1), anterior and posterior margins fine, lateral margins curved, hind angles marked, posterior margin convex with almost straight area at middle, anterior margin strongly developed forward and hiding the head. Elytra 2.52:1 longer than wide; lateral margin sub-parallel, rounded at distal third, elytral disc moderately convex transversely and strongly descending in the distal portion; epipleura wide, of constant width throughout almost its length, sides convergent at the apex, surface glabrous and almost flat, internal margin with denticles. Metasternum convex, grooved medially with two basal, divergent processes with brush-like short rows of setae. Legs: all tibiae with short spines at external margin; tarsomeres with abundant ventral and apical spines.
Abdomen. Ventrite V flat with slightly concave distal margin; ventrite VI with two flat, transverse, subcontiguous plates; last tergite nearly square, with rounded distal angles and posterior margin subacuminate medially, its apodemes moderately long, pubescence thick and short, scattered (Fig. 2b); segment IX (spicular fork) very fine, weakly sclerotized, with fine sternal arms and long apodeme (Fig. 2i). Genitalia: parameres sub- cylindrical, rounded at the apex, sides convergent and fused ventrally, in obtuse angle with tegmen (Fig. 2c, d, e); tegmen with dorsal flange at the base of the parameres, tegminal arms thick, first sub-parallel and after curved and convergent medially, apodeme dorsal and laminated, tegminal plate sclerotized, extended to the base of the apodeme (Fig. 2c, e); median lobe sub-cylindrical, strongly curved, apex acuminated, phallotreme grooved, apodeme enlarged (Fig. 2f, g, h).
Females: Average body length 6.4 (range: 5.0–7.0 mm, n=5) body oblong, sides sub parallel, length: width ratio 2,08:1. Body dark-testaceous, pronotum black, with edges lighter, pubescence dense, dark, short, fine and inclined; elytra dark or light brown with sparse short and thick hairs (Fig. 1b).
Head. Black, including eyes as wide as the anterior margin of pronotum (1:1); fine sparse punctuation at the vertex; antennae shorter than the pronotum (0.65:1), with five medially dilated preapical antennomeres (Fig. 2a) and densely pubescent on inner side.
Thorax. Pronotum as wide as long (1.02:1), slightly convex transversely and moderately convex longitudinally, base wider than apex (1.9:1) and almost as wide as humeral region (0.96:1), anterior and posterior margins finely carinated, lateral margins curved, hind angles rounded, posterior margin slightly convex at middle, anterior margin with a small projection forward. Elytra 2.79:1 longer than wide; lateral margin sub-parallel, rounded at distal third, elytral disc moderately convex transversely and slgthlty descending in the distal portion; epipleura wide, of constant width throughout almost its length, sides convergent at the apex, surface glabrous and almost flat, internal margin with denticles. Metasternum convex slightly grooved medially with two small basal promontories. Legs: all tibiae with scarce short and fine spines at external margin, tarsomeres with scarce ventral and apical spines.
Abdomen. Ventrite V with distal margin slightly convex medially; ventrite VI with two flat, transversal, subcontiguos plates, apodeme elongate (Fig. 3a). Genitalia: ovipositor long, membranous; ventral baculi long, with lateral extensions at the base, 5:1 longer than oblique baculi, ventral lamina with dense pubescence (Fig. 3b); proctigeral baculi thin, 1,5:1 longer than ventral baculi (Fig. 3c), convergent and slightly enlarged at the apex; dorsal lamina with dense pubescence; epiproct subtriangular (Fig. 3c).
Distribution. ARGENTINA: Province of San Juan, Iglesias.
Remarks. Arthrobrachus arquatus n. sp. is very similar to the Chilean species A. tibialis Solier, 1849. Both species share 95% of morphological characters and have more similarity between them than with their sympatric species (Estrada & Solervicens 1999; Estrada 2003, 2016). The male characters such as the brush-like mestasternal setae and genital structures of A. arquatus are the differential characters with A. tibialis (Estrada & Solervicens 1999). From a distributional point of view, A. arquatus was collected in San Juan, Argentina at the Province of Cuyan High Andes (Prepuna) in the South American Transition Zone (Morrone 2004, 2006; Morrone & Ezcurra 2016) and A. tibialis is present in the Central Chilean subregion (Estrada & Solervicens 1999; Arana et al. 2017; Morrone 2015; Romano 2017). Since these areas are known to be biogeographically related due to the rise of the Andes (Mihoc et al. 2006; Morrone 2004, 2006) these species could also be assumed to be sister species as a result of the uplift of the Andes.
description: Published as part of Estrada, Patricia, 2018, A new species of Arthrobrachus Solier, Arthrobrachus arquatus n. sp. (Coleoptera: Melyridae) from the South American Transition Zone, Argentina, pp. 537-542 in Zootaxa 4441 (3) on pages 538-540, DOI: 10.11646/zootaxa.4441.3.7, http://zenodo.org/record/1301466