Leielmis Delève, 1964

Bilton, David T., 2017, A revision of the South African riffle beetle genus Leielmis Delève, 1964 (Coleoptera: Elmidae), Zootaxa 4254 (2), pp. 255-268 : 256-257

Leielmis Delève, 1964

Type species: Helmis georyssoides Grouvelle, 1890

Description. Body form ( Fig. 1 ) short and convex, strongly narrowed both in front and behind.

Head: Relatively narrow, partly retractable, orientated ventrally in life. Labrum short, broader than long and strongly arcuate at anterior margin. Clypeus distinctly broader and longer than labrum, convex, weakly arcuate at lateral margins, concave anteriorly. Frontoclypeal suture weakly arcuate. Antennae 11-segmented, all segments elongate, somewhat flattened dorsoventrally. Mandibles acuminate at apex, prostheca spinose. Maxillary palpi short, spinose, 4-segmented, dorsoventrally flattened, especially expanded segment 3. Palpifer well-developed, galea 2-segmented, long and narrow, flattened. Lacinia larger than galea, flattened, elongate, setose at apex, trapezoidal, with mesal and apical fringes of long setae. Labial palps short, 3-segmented, flattened dorsoventrally, second segment expanded; first segment much shorter than second; third shorter and narrower than second. Mentum transverse, broadly emarginate anteriorly. Ligula trapezoidal, broadly expanded anterolaterally.

Pronotum: Transverse, broadest at base, evenly narrowed to anterior margin; anterior margin approximately half width of posterior margin. Anterior margin arched, arcuate, hood-like, partly shielding head. Lateral margins strongly bordered. Sulci, carinae and gibbosities entirely absent; surface punctate and granulate, granules also present along lateral margins. Granules lost to varying degrees on older specimens.

Elytra: Slightly elongate, strongly bordered, widest approximately one third to one half behind shoulder, narrowing to apex, abruptly so in posterior third. Elytral apices cojointly acuminate. Each elytron with 9 puncture rows, moderately to weakly striate impressed in part; rows 7 and 8 confluent in anterior and posterior thirds. Intervals flat or slightly convex, punctate, with granules apicolaterally. Scutellum trapezoidal, front margin broadly arcuate, sides weakly rounded.

Venter: Prosternum broadly emarginate anteriorly, to receive ventral margin of retracted head. Prosternal process slightly longer than broad, almost parallel-sided over most of length; lateral margins strongly raised. Centre of mesoventrite broadly emarginate to receive prosternal process. Junction of meso and metaventrites with lateral foveae. Metaventrite punctate, broadly concave in middle, more strongly so in males than females; median longitudinal suture evident. Abdomen with 5 ventrites. First ventrite with semicircular carinae encircling posterior margins of metacoxae, fringed with irregular row of coarse, rugose punctures. All ventrites punctate and granulate, at least laterally. Sternite 8 with long, narrow apodeme, approximately 3x length of plate in females; apodeme triangular, similar length to plate, in males. Tergite 8 with broadly rounded apex in both sexes, with apical setal fringes.

Legs: Rather short, tibiae with golden setae on inner surfaces. Meso and metatibiae modified in males. Claws simple.

Hindwing: Approximately 1.5x body length; apical field large, occupying half of total wing length; medial spur narrow, weakly pigmented, not reaching hind margin; medial field occupying two-thirds of basal half of wing, with three distinct veins (MP3, MP4, Cu); anal field small, occupying one third of basal half; hind wing margin with long trichiae throughout.

Aedeagus: Long and slender, corona and fibula absent. Phallobase asymmetrical, shorter than penis and parameres; penis apex acuminate.

Ovipositor: Symmetrical, elongate; proximal gonocoxite as long as or longer than distal; distal gonocoxite elongate, with terminal stylus.

Differential diagnosis. Leielmis can be recognised by the combination of short and strongly convex habitus, strongly narrowed anteriorly and posteriorly; absence of sulci, carinae or gibbosities on the pronotum, which is expanded into a narrow anterior hood; sub-parallel prosternal process; elytra with 9 puncture rows, lacking costae or gibbosities and the simple tarsal claws.

The genus currently includes one described species, plus two new species described below, all of which are endemic to the Cape region of South Africa.

Figures

FIGURE 1. Leielmis species, male habitus. A) L. georyssoides; B) L. gibbosus sp. nov., holotype; C) L. hirsutus sp. nov., holotype. Scale bar = 1 mm.