Atholus torquatus (Marseul, 1854)

dela Cruz, Ian Niel & Ohara, Masahiro, 2023, Revision of the genus Atholus Thomson, 1859 (Coleoptera, Histeridae, Histerinae) from the Philippines with additional records, ZooKeys 1158, pp. 1-26 : 1

Atholus torquatus (Marseul, 1854)

Figs 3 , 15-20 , 21-28 , 29-34 , 41-43

Hister torquatus Marseul, 1854: 587 [India].

Hister (Atholus) torquatus : Bickhardt 1910: 55 [catalogued]; 1917: 194 [catalogued].

Atholus torquatus : Lewis 1906: 402; Mazur 1984: 218; 1997: 134; 2011: 106 [catalogued]; 2015: 1454.

Hister genuae Lewis, 1888: 639; synonymized by Bickhardt 1913 b: 698.

Atholus genuae : Lewis 1906: 402.

Hister mundulus Lewis, 1902: 238; synonymized by Desbordes 1919: 399.

Specimens examined.

8 ♂♂, 14 ♀♀ and 7 exs. Luzon Island , Bataan, Abucay, Gabon , 8 ♂♂ [IC-21-23], 12 ♀♀ [IC-21-53], 5 exs., 14.42329°N, 120.26222°E 570 m a.s.l., 2019-VII-21 [BA-19-IDC-001], I.N. DELA CRUZ leg.; Laguna , Northern Lucena, Kinabuhayan , 2 ♀♀ [IC-21-49], 1989-II, N. Monreal leg. Mindoro Island , Oriental Mindoro, Mt. Halcon , 1 ex., 2005-IV. Palawan Island , Puerto Princesa, Barrio Talabigan , 1 ex., 1979-III-24, K. Wada leg.

Diagnosis.

Atholus torquatus (Marseul, 1854) is recognized with a combination of its interrupted lateral pronotal stria in the anterolateral angle, and fine punctations on the apical portion of its pygidium. This species also possesses remarkable teeth of protibia, increasing in size apically. The structure of the female genitalia of this species is described here for the first time, showing its similarity to the shape of the gonocoxite of A. philippinensis (Marseul, 1854), which is broad and shovel-like.

Re-description.

Male and female. Body length: PEL: 3.13-4.32 mm; APW: 1.11-1.47 mm; PPW: 2.35-2.90 mm; EL: 1.89-2.74 mm; EW: 2.66-3.56 mm. Body (Figs 3 , 15-17 ) oval, moderately convex and black; tibiae, antennae, mouthparts and apical elytral margin rufous.

Head: apical margin of clypeus (Fig. 18 ) short, entire and slightly forward, but anterolateral margin widely crenate; frontal stria rounded, complete and deeply impressed; disk sparsely clothed with fine punctures, separated by 2-3 × their diameter; interspaces with alutaceous microsculpture; occipital fovea absent; labrum dorsally finely punctate, raised and transversely long; short labral fringe (Lackner, 2010) present antero-laterally; mandibles covered with fine and even punctures, outer margin rounded, curved inwardly; sub-apical tooth on left mandible large; mandibular apex acutely pointed; eyes large and convex, clearly visible dorsally.

Pronotum: marginal pronotal stria laterally complete, continuous onto apical angle and behind head; lateral pronotal stria (Fig. 19 ) deeply impressed, slightly crenate and complete; lateral stria rather distant from margin, its basal end abbreviated to basal fourth of pronotal length; apical end bent inwardly behind apical angle; anterior pronotal stria absent; disk with sparse microscopic punctures, wholly covered with alutaceous microsculpture; area behind apical angles bare; posterior margin without row of coarse punctures; ante-scutellar region with a single short longitudinal puncture.

Elytra: basal margin with a row of short, longitudinal striae; elytral epipleuron sparsely clothed with fine punctures, with few, coarse punctures on apical half; marginal epipleural stria present on apical half; marginal elytral stria complete, moderately impressed; external subhumeral stria (Fig. 22 ) generally absent, occasionally noticeable on basal half, abbreviated on basal eighth; internal subhumeral stria absent; oblique humeral elytral stria slightly impressed on basal third; dorsal elytral striae 1-4 (Fig. 21 ) complete; elytral stria 5 present on apical half; sutural elytral stria abbreviated on basal third; elytral disk covered with sparse, fine punctures, separated by 3-4 × their diameter; medio-basal area with alutaceous ground sculpture.

Propygidium and pygidium: propygidium (Fig. 26 ) densely covered with coarse, round and shallow punctures, about 25 µm in diameter, separated by 1-4 × their diameter; interspaces with irregular, sparse and fine punctations, separated by 2-3 × their diameter; surface with alutaceous sculpture; pygidial punctation (Fig. 25 ) similar to that of propygidium, coarse punctures of pygidium becoming sparser and finer apically; interspaces with fine punctations.

Prosternum: prosternal lobe with anterior margin (Fig. 23 ) round; medio-apical end of prosternal lobe ascending; marginal prosternal stria deeply impressed, carinate and shortly interrupted medially; short striae present on both baso-lateral corners; lobe with few setiferous coarse punctures inside and outside of marginal stria on both sides, separated by their 1-2 × their diameter; disk covered with sparse, finer punctures on apical half; prosternal suture lightly impressed; prosternal process covered with few, setiferous fine punctures; lateral sides descending; lateral prosternal striae deeply impressed and complete; lateral disk with several coarse setiferous punctures; basal half narrow; posterior margin of basal lobe strongly emarginated.

Meso- and metaventrite: anterior margin of mesoventrite outwardly arcuate (Fig. 24 ); marginal mesoventral stria complete, carinate, sparsely crenate; stria behind anterolateral angle present; mesoventral disk sparsely clothed with fine punctures separated by 4-5 × their diameter; meso-metaventral suture clearly impressed, complete and medially angulate; lateral metaventral stria deeply impressed, carinate, extending obliquely and posteriorly, united with oblique stria which inwardly extends from basal third of metaventro-metepisternal suture; post-mesocoxal stria extending posteriorly and strongly curved along posterior mesocoxal margin, almost attaining metaventro-mesepimeral suture; punctures of metaventral disk similar to those of mesoventrite; a row of coarse punctures present along inside lateral metaventral stria; longitudinal suture of metaventrite lightly impressed; lateral disk of metaventrite moderately covered with setiferous large round and shallow punctures; interspaces with sparse, coarse to fine punctations; mesepimeron, metepimeron and lateral disk of first abdominal ventrite with dense setiferous, large punctures; interspaces with few coarse to fine punctations; metepisternum with sparse punctures on apical half; punctation of intercoxal disk of first abdominal ventrite similar to that of metaventrite; lateral stria deeply impressed, slightly carinate and complete.

Legs: anterior face of protibia (Fig. 27 ) flattened, dilated and clothed with few, fine ocelloid punctures; basal to median area with weak strigate sculpture; outer lateral margin with four teeth, becoming stronger apically; topped by minute denticles; protarsal groove shallow, with few coarse punctures; anterior protibial stria lightly impressed; inner marginal stria present on basal half, along stria a slightly depressed with row of coarse punctures present; near tarsal insertion with two spine-like tarsal denticles; another one, more distant and longer, located at inner anterior angle; protibial spur moderately long, wider on basal margin, approximately half the length of protarsus; posterior face of protibia (Fig. 28 ) with sparse, fine punctures and strigate ground sculpture from basal to median surface; number of denticles on outer margin eight, one on inner apical angle, outer sublateral margin three or four; median posterior stria moderately impressed and abbreviated on apical end; inner posterior stria moderately impressed with row of sclerotized setae, terminating in three inner posterior denticles; inner margin of setae present on apical half, with a row of short setae on basal half; inner margin with strigate ground sculpture; profemur sparsely clothed with fine, ocelloid punctations; surface with lightly strigate ground sculpture; marginal stria complete; anterior stria present on apical half; femoral stria almost complete, shortened on basal end; posterior margin with large punctations; a row of setae present on both basal and apical ends.

Genitalia: aedeagus (Figs 29 , 30 ) moderately slender, apically slightly curved ventrad; parameres relatively longer, about as almost as thrice the length of phallobase, slightly fused on basal half; median lobe sclerotized; eighth tergite (Figs 33 , 34 ) entire, with longitudinal fold on both lateral sides; ninth tergite (Figs 31 , 32 ) with lateral folds; tenth tergite dorsally longitudinally divided; spiculum gastrale almost as same length as ninth tergite.

Anterior portion of valvifers (Figs 41 , 42 ) paddle-shaped; gonocoxite (Fig. 43 ) slightly elongate, almost as twice as long as broad, shovel-like; inner and outer surfaces differentiated; inner face moderately separated from outer face by elevated lateral ridge; sclerotized setae on apical half of outer face short and slightly dense; inner face with short and sparse setae; apex of gonocoxite with two teeth; gonostyli present, freely articulated; spermathecae multiple, consisting of four sacs; sacs gradually enlarged and elongate, not sclerotized.

Distribution.

Widespread in the Oriental Region including Indonesia, Myanmar, Laos, Thailand, Vietnam, India, Nepal, and China (Sichuan) ( Mazur 2011); Philippines (new record).

Biology.

Atholus torquatus (Marseul, 1854) were collected within the dung of cows located in a higher elevation and semi-forested area. The substrate also differs from A. coelestis (Marseul, 1857), as A. torquatus (Marseul, 1854) was typically observed in soggy, moist dung.

Remarks.

Atholus torquatus (Marseul, 1854) is a quite variable species regarding the external subhumeral stria on its elytra, either clearly marked or totally absent. This character is also mentioned by Desbordes (1917) who mentions the stria can be aberrant. Although the type specimen of A. torquatus (Marseul, 1854) according to the original description possesses no external subhumeral stria, we have examined one specimen with the subhumeral stria present. This corresponds to Desbordes’ (1917) observation. Our observations confirm the variability of this character among specimens ranging across Continental as well as Insular Southeast Asia. On the other hand, male and female genitalia exhibit little variation. We therefore propose to drop the external subhumeral stria as the primary key character for delimiting this species from others.

Figures

Figures 1 - 6. Philippine Atholus, dorsal habitus 1 A. philippinensis (Marseul, 1854) [IC- 21 - 18] 2 A. coelestis (Marseul, 1857) [IC- 21 - 20] 3 A. torquatus (Marseul, 1854) [IC- 21 - 49] 4 A. pirithous (Marseul, 1873) [IC- 21 - 47] 5 A. nitidissimus Desbordes, 1925 [syntype image] 6 A. bakeri (Bickhardt, 1914) [syntype image, No. 1639]. Scale bar: 1.00 mm.

Figures 15 - 20. Atholus torquatus (Marseul, 1854) [IC- 21 - 23] 15 habitus, dorsal view 16 ditto, ventral view 17 ditto, oblique view 18 head, dorsal view 19 pronotum 20 mouthparts, ventral view.

Figures 21 - 28. Atholus torquatus (Marseul, 1854) [IC- 21 - 23] 21 elytra, dorsal view 22 ditto, oblique view 23 prosternal process 24 meso-and metaventrite 25 propygidium and pygidium 26 propygidium (punctation) 27 protibia, dorsal view 28 ditto, ventral view.

Figures 29 - 34. Atholus torquatus (Marseul, 1854), male genitalia [IC- 21 - 23] 29 aedeagus, dorsal view 30 ditto, lateral view 31 ninth and tenth tergites, dorsal view 32 ditto, lateral view 33 eighth tergite and sternite, dorsal view 34 ditto, lateral view. Scale bar: 0.50 mm.

Figures 41 - 43. Atholus torquatus (Marseul, 1854), female genitalia [IC- 21 - 53] 41 dorsal view 42 lateral view 43 dorsolateral view of gonocoxite. Scale bars: 0.20 mm.