Omorgus (Afromorgus) desertorum
Creators: name: Kalawate, Aparna S.
name: Strümpher, Werner P.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Trogidae
Omorgus
Omorgus desertorum

description: Omorgus (Afromorgus) desertorum (Harold, 1872), valid species
(Figs. 12–16)
Type locality. “Aegyptus”.
Type material examined. Lectotype, by subsequent designation (Haaf 1954), male, (MNHN, examined through detailed photographs) (Figs. 12–13): “Aegyptus” | “Ex-Musaeo | E. Harold” || “Muséum Paris | ex Coll. | R. Oberthür | 1952” || “ Lectotypus Har. | det. E. Haaf 1953”. Paralectotype: (RBINS, examined through detailed photographs available at https:// virtualcollections.naturalsciences.be/virtual-collections/entomology/coleoptera/trogidae/trox-niloticus-desertorum-harold-1872 “ Coll. R. I. Sc. N. B. | Egypte Bové | Coll.Ogier de Baulny” || “Dét. Harold 72.” || “ TROX niloticus | desertorum Harold | C.H.S. 1979 | Paralectotype ”.
Trox phylbi Paulian, 1948 (junior synonym of Omorgus (A.) desertorum), paratype, male (MNHB, examined through detailed photographs) (Figs. 17–18): “ Arabia: | Hijaz, | Mecca. | 25.IV.1932 | H.St.J.B.Philby. ” || “Brit.Mus. | 1932-386” || “Museum Paris | Coll. Paulian ” || “PARATYPE” || “ Trox Philby | Paulian, 1948 | PARATYPE | D. Král det. 2021”.
Additional material examined. SAUDI ARABIA: Hajez, Raghama [Abraq Al Raghamah, 21°28′N 39°17′E], ii–xii.1927, H. St. JB. Philby lgt. (2 specimens, NHMB); Mecca District, 15.xi.1931, H. St. J. Philby lgt. (1 specimen, TMSA); BAC Camp, Khamis Mushayt, [18°18′N 42°44′E], 1977, 2000 m, Büttiker lgt. (1 specimen, TMSA). YEMEN: Arabia, Lahej [Lahij: 13°03′N, 44°53′E], Percival & Dodson lgt., 1900-36 (3 specimens, TMSA; Figs. 14–16); Arabia, Lahadj [Lahij: 13°03′N, 44°53′E], Dr Martin lgt. (4 specimens, NHMB, SAMC); East Aden Prot. [Protectorate], Seiyun [15°58′N 48°47′E], 9.vii.1956, J. Roffey lgt. (2 specimens, TMSA); Taiz [13°34′N 44°01′E], 1963, G. Benardelli lgt. (1 specimen, NHMB).
Redescription. Body shape. Strongly convex, elongate oval with almost parallel elytral margins, elytral profile convex, attaining maximum height behind the middle, strongly declivous posteriorly. Length 13–17 mm, width 8–10 mm.
Colour (Figs. 12, 14). Matt black, surface of head, pronotum, legs, elytral margins and parts on the ventral side with light brown to greyish tomentose coating. Body setae light brown.
Head (Figs. 12, 14). Clypeus obtusely triangular, surface sculpted with discrete round punctures, space between punctures approximately equal to diameter of punctures, each puncture with a short stout seta, surface between punctures tomentose, disc slightly convex, medio-laterally strongly depressed on either side, apex of clypeus acute, rounded, margin strongly reflexed, thick, round, with short stout setae. Frons raised with two prominent round central tubercles; surface and tubercles sculpted with discrete round punctures, punctures close, surface between punctures tomentose. Genal angles acute, recurved, surface sculpted with irregularly shaped punctures; gena and genal margin with scattered, short setae. Eyes large and bulbous, hardly visible in dorsal view. Antennal scape elongate, stout, surface coarsely punctured, with long straight brown setae; pedicel attached subapically; antennal club and setae fulvous. Setae around mouthparts dense, rust-brown.
Pronotum (Figs. 12, 14): Attenuated anteriorly; length of pronotum slightly less than one third of elytral length, total pronotum width narrower than elytron width, pronotum widest behind middle. Lateral margins broad and flat, evenly rounded, margin denticulate, with short stout setae; anterior angle obtuse. Base of pronotum truncate behind posterior angles, base slightly projecting backward with distinctly produced posteromedian lobe (opposite scutellum), base weakly sinuated on either side of lobe; basal margin weakly marginate, smooth. Surface tomentose, coarse, densely punctate, each puncture bearing a short stout seta; tubercles with rounded punctures, irregularly spaced, space between punctures varies from less than diameter of punctures to twice the diameter of punctures. Median discal area raised, stretching almost entire length of pronotum, broadly flattened anteriorly, strongly declivous on sides. Pronotal disc with 2 broad elevated median longitudinal ridges. Ridges high, subparallel, partially converging posteriorly. Median pronotal depression distinct, deep, almost entire, fairly evenly wide, shallow anteriorly, deepest at middle. Medial basal tubercles prominent, slightly laterally offset, partially fused to median ridges, connected with lateral basal tubercles by low marginal transverse ridge; anterior and lateral basal tubercles round; basal (larger) and apical (smaller) lateral tubercles broad, fused forming distinct broad sinuous ridge on either side.
Scutellum (Fig. 12): Hastate, almost equal in width and length, marginate, surface finely sculpted, mediobasally depressed, apex raised, distal half of scutellum and margins tomentose.
Elytra (Figs. 12, 14): Elongate, sub-globular, convex, length of elytra equals of 3.2 pronotum length, lateral margins subparallel with narrow flat rims, tomentose bearing row of fine short setae, margin dentate. Humeral calli prominent bearing small tubercles with short setae, humeral angles obtuse. Sutural margin raised, surface smooth, margin with small weakly raised elongate to oval tubercles (sometimes round), tubercles smooth, close, distributed along length of margin. Elytral costae distinct, costae marked by rows of oval to elongate smooth/shiny tubercles of similar height; those on odd numbered costae mostly isolated but sometimes partially connected with weak ridge; those on even numbered costae partially fused to form ridges. All tubercles with posterior tomentosity and short setae, tubercles often produced posteriorly into narrow, short to elongate tomentose ridges (tomentosity often worndown in older specimens). Apical callosity present on third and fourth costal intervals at top of elytral declivity. Intercostae marked by row of round punctures, puncture regularly spaced over length of elytra. Elytral surface matt, mostly smooth, elytral profile convex, attaining maximum height behind middle.
Metathoracic wings: Complete.
Legs (Figs. 12, 14). Protibia straight, outer margin with single distinct median tooth and three to four smaller basal teeth; protibia dorsally keeled; tibial spur stout, pointed forward, apex slightly curved downward, spur as long as three basal tarsomeres combined; dorsally outer tibial surface smooth, coarsely punctate, punctures coalesced; inner tibial surface (top lateral) slightly concave, glabrous, punctate; row of large puncture running closely parallel to the outer and inner margins, punctures close, each with thin long seta; inner tibial surface (lower half) slightly convex, glabrous, punctate; running parallel to lower margin row of punctures, each with long thin seta; ventrally semi-flattened, submedially marginate with row of punctures, each with long seta, inner section glabrous, sparsely setose, surface finely reticulate; outer section coarsely punctate, each with short stout seta. Tarsal segments smooth; tarsomeres 1–4 subequal in length, tarsomere 5 as long as tarsomeres 2–4 combined; tarsomeres 2–5 with short sparse setal brushes, tarsomere 5 with two claws, simple, equal. Mesotibial and metatibial surfaces rugose, punctate, each puncture with long stout seta; outer margin of mesotibia distinctly dentate, outer margin of metatibia weakly dentate; meso- and metatibia with two apical spurs on inner margin; upper spur longer than lower spur; outer margin on apex of meso- and metatibia with row of closely spaced fine short backward pointing setae. Mesotarsi and metatarsi smooth, with short setal brushes, tarsomeres 1–4 subequal in length, tarsomere 5 as long as tarsomeres 3 and 4 combined; distal tarsomere with two claws simple, equal.
Male genitalia (Figs. 15): Genital capsule symmetrical, almost quadrangular shaped, trilobed, sclerotized. Phallobasis, very broad, sclerotized, slightly arched and fused dorsally. Parameres are stout, apically broad and thick, narrowing at the apex, tips are blunt. Phallus broad, apex tapering apically; in dorsal aspect phallus strongly declivous on apical third, declivity projecting dorsolaterally forming two large raised, elongated humps; apex divided into two symmetrical rounded lobes.
Differential diagnosis. Omorgus (Afromorgus) desertorum (Harold, 1872), was previously regarded as a subspecies of Omorgus (A.) niloticus (Harold, 1872) (Haaf 1954; Scholtz 1980). However, we found the consistent differences in the external morphology and the male genitalia between O. (A.) desertorum, and O. (A) niloticus sufficient to consider them to be valid species. The most important difference between them is in the shape and arrangement of the costal tubercles on the elytra. In Omorgus (A) niloticus the costal tubercles are roughly the same height and size, usually round (sometimes oval), close, separated (not distinctly fused). In Omorgus (A.) desertorum the costal tubercles are also of similar height, but usually oval to elongate (sometimes round) in shape; the tubercles on the odd numbered costae are isolated, whereas those even numbered costae partially fuse to form ridges (compare Fig. 14 and Fig. 55). [Note: Adult specimens are often encrusted with a layer of environmental dirt which obscures the external characters. To clarify the elytral difference between the two species it may be necessary to remove the layer dirt and debris covering adult specimens. Guidelines to achieve this are presented in Strümpher & Stals (2023)].
The male genitalia of the two species are very similar to each other, but we found the following difference useful to distinguish between the two species. Omorgus (A.) desertorum have the parameres apically broader and thicker, whereas the parameres in O. (A.) niloticus are narrower and thinner. Furthermore, the phallus in dorsal aspect is much broader and less tapering apically in O. (A.) desertorum when compared to O. (A.) niloticus which have the apical section narrower and more tapering apically (compare Fig. 15 and Fig. 56). Our observations are also consistent with those of Haaf (1954) and Scholtz (1980b).
Current distributional data suggest that both species have overlapping distributions in northeast Africa (Egypt and Ethiopia), however moving southwards the two species display a vicariant distribution between the Arabian Peninsula and the Horn of Africa. With Omorgus (A.) desertorum largely confined to the southwestern portion of the Arabian Peninsula (on the eastern side of the Red Sea) (Scholtz 1980 a, b; Král & Batelka 2017), and O. (A.) niloticus occurring around the Horn of Africa (on the western side of the Red Sea) with range extensions into East and northeast Africa (Scholtz 1980b; Král et al. 2023). Further collection of voucher specimens in the region will be necessary to fully understand the extent of their distributions.
Distribution. For details see the catalogue.
description: Published as part of Kalawate, Aparna S. & Strümpher, Werner P., 2024, Catalogue of species of the subgenus Afromorgus Scholtz, 1986 (Coleoptera: Trogidae: Omorginae) known from the Oriental and Palaearctic Regions, including a description of one new species from the Deccan Plateau in India, pp. 21-63 in Zootaxa 5437 (1) on pages 26-28, DOI: 10.11646/zootaxa.5437.1.3, http://zenodo.org/record/10959360