Tetragonoderus arcuatus Dejean 1829
Creators: name: Kavanaugh, David H.
name: Cueva-Dabkoski, Mollie
name: Liang, Hongbin
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Carabidae
Tetragonoderus
Tetragonoderus arcuatus

description: Tetragonoderus arcuatus Dejean
Figures 9, 13B, 14B, 15B, 16B, 17B, 18 A-B, 22, and 23.
Tetragonoderus arcuatus Dejean, 1829:495. LECTOTYPE, here designated, a female, deposited in MNHN and labeled: “ Egypte ” [handwritten]/ “TYPE arcuatus” [red label]/ “arcuatus Dejean Egypte Coll. Dejean” [handwritten, white label with black border]/ “ LECTOTYPE Tetragonoderus arcuatus Dejean 1829 design. by D.H. Kavanaugh & M. Cueva-Dabkoski 2022” [red label]. Type locality: Egypt [but Dejean viewed this record as uncertain]. Chaudoir, 1876:38; Felix, 2009:116; Assmann et al., 2015:57; Bousquet (2017:498).
Tetragonoderus cardoni Bates, 1891:338. HOLOTYPE, a female, deposited in MNHN. Type locality: India, Jharkhand, Konbir. Bates 1892:416. Synonymy by Andrewes, 1921:150.
Notes on nomenclature and types. In his original description, Dejean (1829) was unclear with regard to how many specimens he had examined (Thierry Deuve, personal communication). He noted that he had received material from Klug and that he had not seen a male specimen. In addition to a single female specimen in MNHN, there are four specimens from Egypt in ZMHB, which were probably part of Klug’s original series and include one male (Bernd Jaeger, personal communication). It seems most likely that Dejean saw only the single female specimen now deposited in MNHN, but we cannot be sure. Consequently, we designate that female as lectotype (International Code of Zoological Nomenclature, Recommendation 73F).
When he proposed the synonymy of T. cardoni Bates with T. arcuatus, Andrewes (1921:150) also noted the pronounced variation in the degree of development of the sericeous sheen seen among specimens of this species. Specimens from the study area and adjacent regions appear to have the most markedly sericeous elytra while those from areas to the west, including the type locality (Egypt), have the least sericeous elytra. There is also conspicuous variation in the distinctness and extent of the subapical pale band of spots. In the single specimen from the study area, and also in those from adjacent parts of the eastern end of the range of the species (e.g., Assam, Myanmar and northern Thailand), the subapical pale band of spots is faint to very faint, almost invisible in some specimens, and apparent only on intervals 7 and 8 or extremely faintly visible also on more mediad intervals in some specimens. In contrast, specimens from the western part of the range of the species (i.e., North Africa, the Middle East and Central Asia) have the subapical band much more distinct and extended from interval 2 to interval 8. The female type of T. cardoni is intermediate between specimens from the western part of the species range and those from the study area and adjacent regions in both of these features. Because of this pronounced variation, features noted in the key above and in the diagnosis presented below are applicable specifically for specimens from the study area and adjacent regions.
Adults of several additional Asian taxa presently treated as distinct species are very similar to those of T. arcuatus. These include Tetragonoderus assamensis Jedlička, 1964, Tetragonoderus cinchona Jedlička, 1964, Tetragonoderus intermedius Solsky, 1874, and Tetragonoderus nakaoi Jedlička, 1966. The taxonomic status of these names is currently under review, but none of them have been recorded from the study area and all are more recently described than T. arcuatus. Consequently, none of them would challenge T. arcuatus as the valid name of this species if one or more are synonymized with the latter name in the future.
Diagnosis. Adults of T. arcuatus can be distinguished from those of other cyclosomine species in the study area by the following combination of character states: Body size medium for genus, BL males = 4.9 to 5.1 mm, females = 5.0 to 5.7 mm; forebody uniformly dark, elytra dark without pale markings in basal half, in the study area with faint pale band of spots in apical half (Fig. 9A, mainly visible on intervals 7 and 8, femora dark black or piceous, tibiae paler; dorsal surfaces dull, with slight to distinct bronze/copper metallic reflection, elytra sericeous (silky) and mottled, especially in posterior half, with elytral microsculpture comprised of a complex pattern of transverse, longitudinal, and oblique patches of elongate meshes, most distorted near discal and umbilicate setal pore punctures; pronotum widest at or anterior to middle; elytra slightly to distinctly and obliquely truncate apically, posterior discal setiferous puncture on interval 3 inserted distinctly anterior to level of pale subapical markings; front tarsomeres 1 to 3 without lateral expansions (Figs. 14B, 15B), middle tarsi of males (Fig. 16B) with tarsomeres 1 to 4 broader than in females and with pads of adhesive setae ventrally (Fig. 17B); median lobe of male genitalia (Figs. 18A,B) long and slender, with apical lamella also elongate, slender and rounded apically.
In the study area, specimens of T. arcuatus (Fig. 9A) are similar only to those of T. parviculus (Fig. 11A) but differ from them in having larger body size, elytra with less distinct and more restricted subapical band and distinctly sericeous sheen, and male genitalia with the median lobe more slender and with a longer and narrower apical lamella (refer to key for additional differences).
Habitat distribution. The lone specimen collected in the study area was found in daytime under a stone on an open beach of the Longchuan River on a mix of sandy and rocky substrate and at an elevation of 1445 m. Assmann et al. (2015) found members of this species “on heavy soils close to water in semi-desert areas” in Israel.
Geographical distribution within the Gaoligong Shan. Fig. 9B. We examined a single female specimen from the following locality: Tengchong County: Qushi Township (Xiaojiangqiao, N25.23944° / E098.61667°, 1445 m, 21 October 2003, Liang H.-B. & Shi X.-C. collectors).
At present, this species has been recorded only from the southwestern part of the study area (Core Area 6).
Overall geographical distribution. Fig. 23. The known range of this species as presently conceived extends from North Africa (Niger, Chad, Sudan, Egypt, and Ethiopia) eastward across the Middle East (Israel, Iraq, United Arab Emirates, Oman, and Yemen), Central Asia (Iran and Pakistan), Nepal, India (Bihar, Jharkand, Sikkim, and Assam) Bhutan, Bangladesh, Myanmar, and western China (western Yunnan Province) and south to northwestern Thailand. A large series of specimens (a total of 95 males and females, in IOZ) from Mafang, Lancang County, Yunnan (N22.57925° / E099.99849°, 1723m, W.B. Gu collector, December 2003 - January 2005) represents the eastern most record for this species.
Geographical relationships with other Tetragonoderus species. The geographical range of T. arcuatus overlaps with several other species in different parts of its range, and these relationships will be addressed in a forthcoming review of the Asian Tetragonoderus fauna (in preparation). In the study area, its range overlaps with those of T. elegans, T. parviculus, and T. punctatus, although it has not yet been found syntopic with any of these species. As noted below, T. microthorax (see treatment for T. punctatus) has not yet been recorded from the study area, but its range overlaps with that of T. arcuatus elsewhere and may also do so in the study area.
description: Published as part of Kavanaugh, David H., Cueva-Dabkoski, Mollie & Liang, Hongbin, 2023, Inventory of the Carabid Beetle Fauna of the Gaoligong Mountains, western Yunnan Province, China: Species of the Tribe Cyclosomini Laporte, 1934 (Coleoptera: Carabidae), with Descriptions of Two New Species., pp. 451-491 in Proceedings of the California Academy of Sciences 67 (20) on pages 463-466, DOI: 10.5281/zenodo.11067293