Arocatus Spinola, 1837

Gao, Cuiqing, Kondorosy, Előd & Bu, Wenjun, 2013, A Review Of The Genus Arocatus From Palaearctic And Oriental Regions (Hemiptera: Heteroptera: Lygaeidae), Raffles Bulletin of Zoology 61 (2), pp. 687-704 : 688

Arocatus Spinola, 1837

Arocatus Spinola, 1837: 257 . Type species: Lygaeus melanocephalus Fabricius, 1798 , by monotypy.

Tetralaccus Fieber, 1860: 44 (syn. Stål, 1872: 42). Type species: Lygaeus roeselii Schilling, 1829 , by monotypy.

Microcaenocoris Breddin, 1900: 171 (syn. Deckert, 1991: 365). Type species: Microcaenocoris nanus Breddin, 1900 , by monotypy.

References. — Distant, 1904: 15 (diagnosis, fauna of British India); Stichel, 1957: 81 (fauna of Europe); Stichel, 1959: 314 (catalogue, Europe); Slater, 1964a: 18 (catalogue); Kumar, 1968: 254 (morphology); Putshkov, 1969: 71 (redescription, fauna of Ukraine); Hamid & Meher, 1973: 36 (keyed, redescription); Zheng & Zou, 1981: 17 (fauna of China); Slater, 1985: 309 (diagnosis, redescription, keyed); Slater & O’Donnell, 1995: 3 (catalogue); Péricart, 1999a: 162 (redescription, European fauna); Péricart, 2001: 37 (catalogue, Palaearctic); Ishikawa et al., 2012: 376 (redescription, fauna of Japan).

Diagnosis. — Moderately elongate, nearly parallel-sided. Body usually covered with semidecumbent, moderately long or longer erect hairs, seldom Palaearctic species without erect hairs. Head at least slightly swollen posteriorly to eye; eyes separated from anterior margin of pronotum; ocellus closer to eye than interocular distance; antennal segment IV not or slightly longer than segment II. Pronotum subtrapezoid; punctured except callus and extreme base; impressed and constricted behind callus; sometimes with median carina behind callus; callus moderately swollen, slightly oblique, almost reaching lateral margin at anterior angle of pronotum. Scutellum with T-shaped carina, lateral fovea deeply, coarsely punctured. Fore femur unarmed. Ostiolar peritreme of metathoracic scent gland well developed, protruding, yellow or reddish. Posterior margin of metapleuron straight.

Differential diagnosis. — The eyes are not adjacent with the anterior pronotal angles, and the head is slightly swollen posteriorly to eyes in both Arocatus and the genera of the Achrobrachys Horváth, 1914, Thunbergia Horváth, 1914 and Caenocoris Fieber, 1860 . Arocatus differs from Achrobrachys by the antennal segment II being about as 0.8–1.3 times long as segment IV, and the elongate, nearly parallel-sided body; antennal segment II is about as half long as segment IV and the body is broad and subovate in the latter genus. Thunbergia can be separated from Arocatus by the presence of a short, subapical spine on the fore femur of both sexes, and the distinct collar of the anterior pronotal margin ( Slater, 1978), and the antennal segment II is about as 0.55–0.7 times long as segment IV. The limits between Arocatus and Caenocoris are not distinct. Although the main character, the antennal segment II being “not much” or “much” shorter than IV, was repeated again and again in the literature, it may not be reliable. Slater (1978) thought Caenocoris could be separated from Arocatus by the presence of a short subapical spine on the fore femora of both sexes, and Stål (1872) stated that the former lacks a distinct carina on pronotum.

Emphanisis China, 1925 is also similar to Arocatus in general habitus, but we think it can be distinguished from the latter genus by the body being mainly bronze-coloured, covered with dense golden appressed hairs (erect hairs lacking), the pronotum being rugose, the punctures on the posterior lobe of pronotum being large and linked together, and the much broader abdomen of both sexes.