Rowellacris Ritchie & Hemp, 2025

Genus Rowellacris Ritchie & Hemp n. gen.

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TYPE SPECIES. — Ixalidium usambaricum Ramme, 1929 .

ETYMOLOGY. — This new genus is named in honour of Charles Hugh Fraser Rowell in grateful recognition of his outstanding contributions to the biology and systematics of tropical locusts and grasshoppers over more than sixty years.

DESCRIPTION

See family description. Small to medium size (see Measurements, Tables 8; 10; 11). Males 18.5-24.75; Females 27.5- 33.95. Integument rugose and punctate.

Head

Antennae ensiform, with c. 16-17 segments, from 80% to 115% of combined length of head and pronotum. Fastigium of vertex 1.3 to 1.6 times as long as its basal width, with irregular transverse sulcus at base.

Thorax

Pronotum low tectiform, median carina intersected by 3 sulci, the first often indistinct. Prosternal tubercle transverse, chisel like, with anterior face oblique, apex widening, lateral edges rounded to slightly bilobate, sometimes slightly crescentic in cross-section with anterior margin shallowly concave. Mesonotum, short, occasionally ( R. transiens ( Ramme, 1929) n. comb.) with narrow strap-like tegminal scars, completely fused to integument, sometimes visible projecting from beneath hind margin of pronotum, on one or both sides just above lateral sutures separating dorsum from mesopleura. Metanotum slightly inflated.

Legs

Hind femora moderately stocky (length / max. depth, males: 3.1-3.75, females; 3.35-3.85); hind tibiae with seven outer and nine inner spines; external apical spine absent.

Abdomen

Tergites medially carinate with each segment in lateral view dorsally convex, tergites 1 and 2 slightly inflated; tympanum large, suboval, with ventral margin flattened or slightly concave.

External terminalia ( Fig. 5 D-G) with supra-anal plate divided into basal polygonal portion and movable triangular apical portion. Hind margin of basal portion distinctly sinuous with paired rounded flanges. In R. usambarica ( Ramme, 1929) n. comb. last abdominal tergite (tergite 10) interrupted dorso-medially by basal portion of supra-anal plate; in R. transiens n. comb. tergite 10 continuous and thickened dorsally, with dorsally-projecting digitate median furcula; supra-anal plate strongly rugose; cerci simple, conical, densely covered in sensilla. Subgenital plate bulbous (by comparison to Ixalidium ), of variable length (short in R. obscuripes n. comb.), with attenuate apex.

Male genitalia

Epiphallus ( Figs 13E, F; 14 M-O; 15K-M) bridge-shaped, without ancorae; lateral plates concave in dorsal view; lateral sclerites elongated, irregular in outline, somewhat deflexed postero-dorsally; lophi bilobate, lobes pointed with inner pair directed medially and postero-dorsally, outer pair smaller and laterally directed; ventral margin of bridge forming a membranous cushion; bridge, lateral plates and adjoining membrane with numerous sensory pores.

Cingulum ( Figs 13B, D; 14E, G, H; 15B, C, G). Having sclerotised shell-like zygoma with anteriorly placed paired apodemes distinct (in R. usambarica n. comb. and R. transiens n. comb.), obsolescent (in R. obscu ripes (Miller) n. comb., or absent (in undescribed species from East Usambara Mts); zygoma hind margin medially incurved in R. usambarica n. comb., and R. transiens n. comb., and forming sclerotised lateral horns in R. usambarica n. comb., or roundly excurved ( R. obscuripes n. comb. and R. transiens n. comb.); rami of cingulum, covered by epiphallic membrane, forming inflated mitten-like lateral lobes with sclerotised ectophallic structures visible within, medially concave and externally convex; rami continuous with zygoma dorsally and fusing ventro-laterally with dorso-lateral margins of inflated bulbous ventral lobe. Arch of cingulum present, well-developed, joining zygoma to apical valves of endophallus; dorso-lateral margins of cingular arch bilaterally inflated to form bulbous sub-dorsal lobe, strongly developed and visibly projecting caudad from beneath cingulum in dorsal view in R. usambaricum n. comb. and R. transiens n. comb., less developed and somewhat variable in different populations of R. obscuripes n. comb.

Endophallus ( Figs 13D; 14E, J-L; 15F, H-J). In two sections with visible articulated break, paired endophallic apodemes separated apically, laterally flared dorsally, fused and medially ridged throughout most of their length; ejaculatory sac obsolete, reduced to a slight widening of the ejaculatory duct, before entering fused endophallic apodemes; apical endophallic sclerites fused, laterally compressed, slightly to moderately upcurved, forming tubular aedeagus enfolding phallotreme, within membranous sheath continuous with rami of cingulum; apex of aedeagus excurved, projecting dorsally beyond rami and ventral lobe; spermatophore sac reduced, situated dorsally at proximal end of apical sclerites, anterior to arch of cingulum.

Female genitalia ( Fig. 12).

Spermatheca with three diverticula ( Fig. 12 A-C) arising from vestibule one above another: most ventral one short, sac-like, widening distally; middle one elongate sac-like, almost as long as dorsal ovipositor valves and apodemes together; dorsal one thin tubular, shorter than dorsal ovipositor valves, with apical and subapical diverticula, each ending in an apical ampulla ( Fig. 12 A-C); vestibule with elongate open slit ventrally between ventral valves of ovipositor ( Fig. 12B).

Coloration ( Figs 2 C-E; 19E, F).

Rowellacris Ritchie & Hemp n. gen. males have similar range of overall patterning to Ixalidium , with paler morphs dorsally buff-coloured, contrasting with darker brown lateral parts of thorax and darker morphs having all paler markings indistinct. Typical patterning includes dorsal longitudinal lateral pale bands beginning behind eyes, converging towards median carina in prozona of pronotum, then either continuous or interrupted by darker pigment, before diverging and continuing obliquely downwards across thoracic pleura to hind coxae; metaepimeron black.Hind femora externally mottled brown or olive grey, darker on upper and lower marginal areas; internal upper marginal area mottled olive grey proximally, becoming darker towards knee, sometimes with pale buff oval marking in proximal half; internal medial area mainly black with pale mark towards knee, sometimes with paler area medially; lower internal carinula and carina and lower marginal area red in proximal three fifths, fading or darkening towards knee. Hind tibia varying from pale greyish buff to grey brown, pale mauve, violet or blackish, but never red; tibial spines black-tipped. Abdomen with lateral shiny black bands reaching from tergite 2 to tergites 5 or 6, fading caudad. Ventral surface of thorax and abdomen pale buff to light brown.

INCLUDED SPECIES

Rowellacris usambarica ( Ramme, 1929) nom. rev., n. comb. Rowellacris transiens ( Ramme, 1929) n. comb.

Rowellacris obscuripes ( Miller, 1929) nom. rev., n. comb.

Rowellacris usambarica ( Ramme, 1929)