Cyclosomus inustus Andrewes
Creators: name: Kavanaugh, David H.
name: Cueva-Dabkoski, Mollie
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Carabidae
Cyclosomus
Cyclosomus inustus

description: Cyclosomus inustus Andrewes
Figures 1, 7, 14C, 16C, 17C, 19, 20
Cyclosomus inustus Andrewes, 1924:464. HOLOTYPE, a male, deposited in NHMUK. Type locality: China, Hong Kong. Csiki (1932:1295); Lorenz (2005:452); Bousquet (2017:498); Wang et al. (2017, 2022).
Notes on types and nomenclature. In his original description of this species, Andrewes (1924:464) indicated that he had compared “ sixteen specimens labeled “ Hong Kong: and “ China ”: these latter include examples in the British Museum, Cambridge University Museum, the “Reise Novara” example, and specimens from my own collection” with specimens of C. flexuosus and C. suturalis. He added that “ As a result of this I think that the Hong Kong examples form a distinct species.” We examined three specimens from “ Hong Kong ”, one labeled “Type” (i.e., the specimen we list above as holotype) and the other two labeled “Cotype”, two specimens from “ China ” labeled “Cotype,” as well as single specimens from Chandipore, (India) and Dom Toum (Laos) labeled “Cotype”. All of these cotypes were mentioned in Andrewes’ description as conspecific, so each of these, as well as any other specimens labeled “Cotype” by Andrewes, should be considered as paratypes of C. inustus.
Diagnosis. Adults of C. inustus can be distinguished from those of all other Cyclosomus species in Asia by the following combination of character states: Body size medium for genus, BL males = 7.3 to 8.0 mm, females = 6.6 to 7.8 mm; body form (Figs. 7A, C, D) more elongate-ovoid (ratio BL/EW = 1.47 to 1.53), with elytra widest at or slightly anterior to mid-length; pronotum (Fig. 14C) relatively longer and narrower (ratio PWM/PL = 2.33 to 2.93) and more broadened basally (ratio PWM/PWA = 1.63 to 1.75), with disc varied in color (rufous to piceous) and lateral pale bands of medium width and well-defined, anterior angles broad, lateral margins not sinuate near anterior angles; free apex of prosternal intercoxal process long (as in Fig.15C); elytral dark pattern varied in both form and color, with dark maculae rufous to piceous in color and with basal and middle bands of average (Fig. 7D) to less than average (Fig. 7A) thickness and continuity or middle band absent (Fig. 7C), preapical dark spot absent or only faintly present (Fig. 7D) in a few specimens (from inland areas in Indochina); elytral striae very deeply impressed, elytral intervals (especially intervals 3 to 5) slightly but distinctly convex; elytral epipleura with long setae only in humeral and subhumeral areas, setae in apical two-thirds distinctly shorter; median lobe of male genitalia long and more slender, with shaft of approximately equal thickness throughout, ventral curvature gradually and only slightly arcuate in apical two-thirds in lateral aspect (Fig. 16C), apical lamella longer, smoothly rounded apically, and not or only slightly narrowed basally in dorsal aspect (Fig. 17C); specimen from southern Asia, from northeastern coastal India, through Indochina, to coastal southeastern and eastern China and Taiwan (Fig. 20).
In his original description of this species, Andrewes (1924) included specimens demonstrating variation among populations in different parts of the range of the species. He noted that a specimen from Pak Lay (Laos) was exceptionally dark and convex and that specimens from Nanoa Island (Guangdong Province, China) were exceptionally small and pale. Our examination of genitalia of males from these areas and the others listed below found that they all have similar overall form but that the shape and length of the apical lamella is slightly varied both within and among populations. Nonetheless, Andrewes concluded that these diverse populations were all conspecific and we tentatively follow him here.
Specimens of C. inustus with the elytral preapical pale spot absent are similar to those of C. marginatus, C. pallidus, and C. vespertilio. They are distinguished from C. pallidus members by their more elongate body form and somewhat narrower pronotum (compare Fig. 14C with Fig. 14E) with lateral pale bands much narrower and lateral areas less broadly flattened. Most (but not all) of these C. inustus specimens have the middle dark band, or at least a vestige of it, evident on the elytra, whereas C. pallidus specimens lack this band altogether (Fig. 9A). Members of C. inustus can be distinguished from those of C. vespertilio by their more elongate body form, slightly broader basal dark band on the elytra, and narrower reflexed lateral elytral margins. Males of these two species also differ distinctly in the shape of the median lobe of the genitalia, with the shaft much shorter and thicker in C. vespertilio males (Fig. 16H) than in C. inustus (Fig. 16C) males in lateral aspect.
Distinguishing specimens of C. inustus from those of C. marginatus is more difficult, at least partly because there are so few specimens of the latter known (just three) that it remains difficult to fully characterize its members. As presently conceived, members of the two species differ slightly in body shape (slightly more elongate-ovoid in C. inustus), pronotal shape (relatively longer and narrower and with narrower lateral pale bands in C. inustus; compare Fig. 14C with Fig. 14D), and length of the free apex of the prosternal intercoxal process (longer in C. inustu s, as in Fig. 15C; medium length in C. marginatus, as in Fig. 15B). Because the lectotype of C. marginatus is a female, we cannot be certain that the male specimen we tentatively identify as that species is conspecific with the type. Genitalia of that male (Fig. 16D and 17 FD) and those of C. inustus (Figs. 16C and 17C) are similar in form but differ slightly in the shape of the apical lamella in dorsal aspect (compare Figs. 17C and 17D). However, the shape of the apical lamella in one of two male specimens of C. inustus from Cambodia is similar to that of the male we identify as C. marginatus, although the two differ in all the external features noted above to distinguish these two species. We certainly need to consider that C. inustus and C. marginatus may, in fact, be conspecific. However, the paucity of material referable to the latter and the uncertainty (see below) about its actual geographical and habitat distributions renders a taxonomic decision in this regard premature at this time.
Those few atypical specimens of C. inustus that we have seen with a faint preapical dark spot on the elytra (Fig. 7D) (see section on Geographical Variation below) are externally very similar to members of C. suturalis and reliably distinguished from the latter only by reference to the male genitalia. The apical lamella of such C. inustus males is rounded and slightly (as in Fig. 17D) to moderately elongate (Fig. 17C), whereas that of C. suturalis males is shorter and bluntly triangular (Fig. 17G). It is certainly possible that these specimens with preapical pale spots from inland localities in Indochina, which we identify here as C. inustus, actually represent a separate, perhaps undescribed species (see below).
Habitat distribution. Waterhouse (1850 -51:104) quoted text from a letter written by J.C. Bowring and dated June 9, 1851 describing his encounter with this species in Hong Kong, the type locality, as follows: “I inclose [sic] a pair of Cyclosomus insularis, White [a nomen nudum], a species I met yesterday morning for the first time. This beetle burrows to some depth in the sand by the seashore; it is very active in its movements, and when exposed on the surface disappears beneath the sand with truly wonderful rapidity, diving down head foremost. I captured about twenty specimens by turning up the sand for some distance to a depth of five or six inches”. Wang et al (2017) reported on the discovery of C. inustus in coastal sun dune areas (Fig. 19) in northern and northeastern Taiwan, and Wang et al. (2022) found addition coastal dune localities in Taiwan and on Kinmen Island just off the Chinese mainland. They also searched extensively for these beetles in similarly exposed sandy habitats along river and lake shores in both areas but without success. Additional records (see below) from Fuzhou and Ningbo (China), and probably also from Ban Hua Hin (Thailand), and Chandipur (India) likely also represent coastal sandy beach or dune occurrence. At least in Taiwan and on Kinmen Island, this species appears to be restricted to coastal sandy areas.
The habitats for specimens collected at inland localities in Indochina (i.e., in Cambodia, Laos, and central Thailand) are unknown but likely were along streams with exposed sandy banks. This may reflect either a broader habitat range for C. inustus in this region or a species difference between these inland populations and the coastal C. inustus populations.
Geographical distribution. We have examined a total of 41 specimens (23 males and 18 females) from the following localities: CAMBODIA: Steong Treng, “Hat Baoho” (7-10 May 2012, J.K. Li collector [two males; NHMUK]). CHINA ([one male and two females; NHMUK]), ([two males; NHRS]), ([one female; IRSNB]): Fujian: Fuzhou (31 May 1935 -36, M.S. Yang collector [three females; NHMUK]); Guangdong: Nanoa Island (J.J. Walker collector [two males and one female; NHMUK]); Hong Kong: ([two males and one female; NHMUK]); Zhejiang, Ningobo ([one female; MFNB]); “W China ” ([one male; NHMUK]. INDIA (one male; MFNB]), ([one male and one female; NHMUK]): Odisha: Chandipur (near Balasore, 3-7 June 1915, F.H. Gravely collector [one female; NHMUK]). LAOS: Champasak Province, Khone area (Dom Toum, 24 October 1916, R.V. de Salvaza collector [one male; NHMUK]); Sainyabuli Province: Pak Lay (January 1916, R.V. de Salvaza collector [one female; MFNB]). TAIWAN: New Taipei City: Shihmen (Lingshanbi, 3 October 2013, L.J. Wang collector [six males and five females; CAS]). THAILAND: Prachuap Khiri Khan Province: Ban Hua Hin (15 January 1990, J. Nielsen collector [one male; CAS]); Uthai Thani Province: Lan-Sak (25 km NW, 110 m, December 1990 [two males; MFNB]). Specimens with illegible locality data: ([one male; MFNB]).
As presently conceived, the known geographical range of C. inustus (Fig. 20) extends across Southeast Asia from the coast of India (Odisha State) on the Bay of Bengal eastward to coastal Fujian, Guangdong, and Zhejiang provinces (China) and Taiwan, and south into Cambodia and Thailand. This species has not yet been recorded from Myanmar, Vietnam, or Hainan Island (China), but it is likely to occur also in these areas.
Geographical variation. Most specimens of C. inustus from localities in Taiwan and on Kinmen and Nanao Islands (Guangdong) are smaller than those from mainland areas and have the elytral dark pattern paler (rufous or rufopiceous rather than piceous) and reduced in extent (see Wang et al. 2017 for images showing this variation), with the middle dark band absent from some specimens (Fig. 7C). At least some specimens from inland parts of Indochina (Cambodia and Thailand) have a small and faint preapical dark spot present (Fig. 7D). Specimens from these areas (and Laos) are more darkly pigmented (pronotum piceous rather than rufopiceous or rufous, middle dark band of the elytra black rather than rufopiceous). However, all of these specimens have male genitalia similar to those of other C. inustus males.
Geographical relationships with other Cyclosomus species. To date, this species has not been found syntopic with any other congeneric species; however, it may be sympatric with C. flexuosus, C, marginatus, and/or C. suturalis in the western part of its range, but none of these relationships have been demonstrated to date.
description: Published as part of Kavanaugh, David H. & Cueva-Dabkoski, Mollie, 2023, A Review of Genus Cyclosomus Latreille (Coleoptera: Carabidae: Lebiinae: Cyclosomini) in Asia., pp. 493-537 in Proceedings of the California Academy of Sciences 67 (21) on pages 507-511, DOI: 10.5281/zenodo.11512952