Oligoneuriopsis lawrencei Crass, 1947

Barber-James, Helen M., Zrelli, Sonia, Yanai, Zohar & Sartori, Michel, 2020, A reassessment of the genus Oligoneuriopsis Crass, 1947 (Ephemeroptera, Oligoneuriidae, Oligoneuriellini), ZooKeys 985, pp. 15-47 : 15

Oligoneuriopsis lawrencei Crass, 1947 Figures 2 , 3 , 4 , 14D , 15D

Oligoneuriopsis lawrencei Crass, 1947: 53, figs 3, 4.

Material examined.

Neotype: South Africa • 1N; Eastern Cape Province, Tributary of Tyume River, below Tor Doone, Hogsback; 32.5778°S, 26.9347°E; alt. 1445 m a.s.l.; 29 Feb. 1992; F.C. de Moor leg.; AMGS; GEN 1097A; H.M. Barber-James design., 2020. This specimen was chosen because it comes from one of Crass (1947) 's original localities.

Other material: South Africa • 1N; Eastern Cape Province, Tsitsa River, at "The Falls"; 31.0214°S, 28.4819°E; alt. 1140 m a.s.l.; 26 Mar. 1991; F.C. de Moor & H.M. Barber leg.; AMGS; ECR 92AE • 6N; same locality; 28 Mar. 1993; F.C. de Moor & H.M. Barber-James & K. Martens leg.; AMGS; ECR 134A • 12N; Eastern Cape Province, Nqancule River, at Waterval; 31.3672°S, 28.2167°E; alt. 1220 m a.s.l.; 24 Mar. 1991; F.C. de Moor & H.M. Barber leg.; AMGS; ECR 86A • 6N; Eastern Cape Province, Nqancule River, at Albany; 31.3486°S, 28.2153°E; alt. 1240 m a.s.l.; 5 Mar. 1991; F.C. de Moor & H.M. Barber leg.; AMGS; ECR 88A • 1N; Eastern Cape Province, Kettle Spout waterfall, Tyume River tributary, Hogsback; 32.5500°S, 26.9500°E; alt. 1835 m a.sl.; 19 May 2007; F.C. de Moor and N. Phaliso leg.; AMGS; GEN 1845A • 3♀, 4♂, 1N; KwaZulu-Natal, Klein Mooi River, at Durleigh Farm; 29.2283°S, 29.8997°E; alt. 1392 m a.s.l.; 15 Mar. 1995; C. Dickens; AMGS; MOI 29BS • 3♀ 4♂; same locality; 3 Apr. 1995; F.C. de Moor leg; AMGS; MOI 35B.

Male imago.

Lengths. Body: up to 14.8 mm; forewing: up to 14.9 mm; cerci: up to 17.0 mm; caudal filament: up to 12.8 mm.

Vertex light brown, frontoclypeus pale cream, broadly rounded apically, compound eyes black, base of ocelli black, ocelli whitish, antennae with scape and pedicel pale cream, first segment and flagellum light brown. Pronotum light brown, margins suffused with dark brown pigmentation. Pterothorax light brown, with pale cream-coloured unsclerotized line between meso and metanotal plate. Mesoscutellar filaments present. Forelegs shorter than mid or hind legs, with outer margin of femora, tibiae and tarsi dark brown, otherwise uniform pale brown colour; mid- and hindlegs cream to light brown, no distinct markings. All three pairs of legs appear to be functional. Tarsal claws paired, blunt. Wings (Fig. 2 ), when folded, light brown, almost whitish when unfolded. Forewing typical of the genus, with five groups of veins: Sc+RA, RSa+iRS, RSp+MA1, MA2+MP1, and a forked MP2+CuA - CuP vein. Subcostal field with numerous transversal veins, those issued from RA not reaching iRS in the distal forth of the length, those between iRS and MA1 only present in the proximal half.

Abdominal segments uniformly creamish, without distinct patterns, except tergites VII, IX, and X light brown; lateral margins with spine-shaped extensions from segment III to IX, of increasing length towards the posterior. Gonostyli whitish to grey, cerci whitish. Gonostyli 4-segmented, the basal one ca. 3 × the length of segments 2 to 4 combined. Penis lobes almost triangular, with characteristic sclerotized proximal process ending in a simple projection; apex of the lateral longitudinal lobe of penis in a small club-shaped sclerite (Fig. 3 ). Cerci with whorls of long setae at each junction (not figured).

Female subimago.

Lengths. Body: up to 17 mm; forewing: up to 18.8 mm; cerci: up to 7 mm; caudal filament: up to 4.5 mm. Colouration as in the male; tibiae and tarsi of all legs appear to be functional. Cerci light to medium brown. Posterior margin of sternite IX deeply concave and rounded.

Nymph.

Lengths. Body up to 15 mm and 18.5 mm in male and female nymphs respectively; cerci (and caudal filament) up to 9.2 mm (4.0 mm) and 10.1 mm (3.5 mm) in male and female nymphs respectively. General colouration light to medium yellow-brown (Fig. 4A ), with dark brown dorso-medial markings, better developed in mature male nymphs than in immatures or females. Head (Fig. 4B ) medium brown, with maculation between the compound eyes. Ventrally, head a uniform pale cream colour. Gills at base of maxillae forming a “beard” ventrally at base of head, of similar colour to head in Hogsback specimens, orientated in one plane, parallel to length of body. Pro and mesonotum medium brown, with pale cream-coloured maculae. Legs light brown, femoro-tibial articulation darker, setae of forelegs noticeably darker brown than the legs. Femur and tibia of foreleg shorter than those of mid or hind leg, in all cases, femora and tibiae subequal in length. Setae on the outer margin of mid and hind femora well developed, slightly decreasing in size and reaching the apex (Fig. 14D ). Tibiae and tarsi with long, even fringe of setae along entire dorsal margin, interspersed with occasional short spine-like setae. Abdominal tergites uniformly medium brown, each with darker brown marking medially; sternites uniform pale brown, with no markings. Dense patch of posteriorly orientated setae ventromedially on abdominal sternites II-IV, much reduced patch on segments V, further reduced on VI. Gills II-VII almost subequal in size, gill I smaller. On all gills except for gill I, fibrillae shorter than lamella length. Lamella of gill I less than half the length of the fibrillar portion. Lamellae II-VII with long and thin setae on their distal inner margin (Fig. 15D ). Posterolateral spines of the abdomen increasing in size posteriorly. Whole nymph (dorsal aspect) and gills as illustrated by Agnew (1980). Cerci uniformly medium brown, caudal filament paler brown.

Intraspecific variation.

Specimens from KwaZulu-Natal are darker brown in colour than specimens with more southerly distribution, and first three abdominal segments darker brown in colour dorsally than remaining segments; faint paired median spots visible on the last five abdominal tergites in some KwaZulu-Natal nymphs. The head also possesses a dark brown marking present on the frons between the ocelli, and maxillary gills are much paler in colour relative to head capsule in KwaZulu-Natal specimens.

Affinities.

Winged stages were collected from the same locality as the nymphs in one instance, allowing association of the life stages. Imagos were seldom flying at the times of collection. Nymphs of O. lawrencei have a broadly rounded fronto-clypeal region, which easily distinguishes them from O. jessicae and O. elisabethae , both of which are more pointed in shape. Head very slightly carinate, less so than in O. elisabethae . Note that this is unlike the strong carination seen in Elassoneuria .

Habitat preference.

Found under large boulders (400-500 mm diameter) in swift current, often in rivers with bedrock substrate.

Known distribution.

South Africa.

Figures

Figure 2. Oligoneuriopsis lawrencei, fore- and hind wings. Scale bar 0.5 mm.

Figure 3. Oligoneuriopsis lawrencei, ventral view of lower abdomen of adult male, showing lateral extensions of segment IX, gonostyli and penes. Black arrow: Apex of the lateral longitudinal lobe of penis. Grey arrow: Proximal process of penis. Scale bar 0.5 mm.

Figure 4. Oligoneuriopsis lawrencei A whole nymph, dorsal view B dorsal view of head. Scale bar: 5 mm (A).

Figure 14. Hind femora of representative Oligoneuriella (A-C) and Oligoneuriopsis (D-F) species A Oligoneuriella rhenana B Oligoneuriella pallida C Oligoneuriella skoura D Oligoneuriopsis lawrencei E Oligoneuriopsis skhounate F Oligoneuriopsis orontensis.

Figure 15. Outline of gill plate III of representative Oligoneuriella (A-C) and Oligoneuriopsis (D-F) species A Oligoneuriella rhenana B Oligoneuriella pallida C Oligoneuriella skoura D Oligoneuriopsis lawrencei E Oligoneuriopsis skhounate F Oligoneuriopsis villosus.