Derelomus bivirgatus Marshall, 1951

Derelomus bivirgatus Marshall, 1951

Fig. 28 View Fig

Derelomus bivirgatus Marshall, 1951: 841 .

Diagnosis

In the D. ephippiger group, this species can be distinguished by the strong curvature of the rostrum in lateral view ( Fig. 28B–C View Fig ) and the sides of the elytra are very convex in the male. Such a strong curvature of the rostrum is only met in D. brevis , but in the latter species, the rostrum and the body are shorter and the sides of the elytra are moderately convex in the males ( Fig. 21A–C View Fig ). GenBank accession numbers for the corresponding DNA barcodes: PV698441–42–43.

Material examined

Lectotype (here designated)

KENYA • ♂; “Type [red label]” “ Mac Arthur; Makindu [Kenya, 2°16′37.2″ S 37°49′08.4″ E] 5 37 [ May 1937]” “Press by; Com Inst Ent; B M 1951-179” “ Derelomus ; bivirgatus Mshl. ; type ♂” “LECTOTYPE ♂; Derelomus ; bivirgatus ; Marshall, 1951; Haran des. 2025”; NHMUK.

GoogleMaps

Paralectotypes

KENYA • 6 ♂♂, 7 ♀♀; Makindu ; 2°16′37.2″ S, 37°49′08.4″ E; May 1937; Mac Arthur coll.; NHMUK.

GoogleMaps

Other material

REPUBLIC OF SOUTH AFRICA – KwaZulu-Natal Province • 5 ♂♂, 4 ♀♀, 2 specs (preserved in ethanol); St Lucia; 28°22′59.8″ S, 32°24′33.4″ E; 5 Jan. 2019; J. Haran coll.; male inflorescence of Phoenix reclinata ; JHAR02044 ; CBGP GoogleMaps • 2 ♀♀; Kloof; 29°47′06.0″ S, 30°50′10.8″ E; Aug. 1926; R.E. Turner coll.; NHMUK. GoogleMaps

UGANDA • 2 ♂♂, 1 ♀; Kawanda; 0°25′12.0″ N, 32°32′24.0″ E; 15 Feb.–6 Mar. 1958; P. Whalley; mercury vapor light trap; NHMUK. GoogleMaps

Redescription ( ♂)

MEASUREMENTS. Body length 2.5–3.2 mm.

COLOR. Body integument pale brown, club, apex of rostrum, post-ocular area, scutellar shield and median line of pronotum usually darker or dark brown, basal 3/5 of 4 th interstriae and 1 st interstriae at 3/5 of length generally dark brown, forming empty rectangle on elytra; dorsum with minute recumbent whitish setae, glabrous in appearance.

HEAD. Rostrum slightly longer than pronotum in lateral view (1.07×), strongly and regularly downcurved, almost forming quarter circle; in dorsal view about 3.5–3.7 × as long as wide, integument densely punctate, forming 5 longitudinal carinae; antennae inserted at apical ¼ of length in lateral view; head capsule densely punctate in dorsal view, forehead flat; eyes convex, exceeding lateral curve of head capsule in dorsal view; antennal funicle with first segment 2 × as long as wide, as long as segments 2–3 together, 3–7 transverse.

PRONOTUM. Wider than long (W:L ratio: 1.54), widest near base or at basal ⅓ of length, a little narrower there than elytra at humeral angles (0.83 ×), side rounded, converging apicad, forming notch and blunt tooth near middle of length; apical constriction distinct, about as deep as width of scape in middle of length; integument with punctures rounded, space between punctures rough, shiny, micropunctate, wider or narrower than diameter of punctures in middle, narrower laterally.

METATHORAX. Metanepisterna with recumbent white setae, non-contiguous.

ELYTRA. A little longer than wide (W:L ratio: 0.90); sides strongly convex, widest near basal 2/5 of length; humeri not distinct from the lateral curvature of elytra; apex rounded, notched or jointed at level of suture; striae with punctures about ⅓ to ¼ as wide as width of interstriae; interstriae flat, 5 slightly raised on basal 3/5 of length; scutellar shield rounded, generally darker than elytra, coated with small recumbent scales not concealing integument.

ABDOMEN. Underside uniformly pale brown, with minute recumbent whitish setae, not contiguous. Stridulatory plate with lines of 9 granules more than ¾ as long as median line from base, space between granules 2–3 × as wide as diameter of a granule. Central sclerotized area isodiametric, truncate at base ( Fig. 28E View Fig ).

LEGS. Profemora moderately thickened near middle of length; protibiae with external margin straight, internal bisinuate, setae on apical half of internal margin recumbent, shorter than length of claws; claws simple.

TERMINALIA. Body of penis elongate (W: L ratio: 0.24), about 2× as long as apodemes; sides subparallel, in dorsal view, narrowing apicad in apical ¼ of length, apex rounded; in lateral view curvature moderate but stronger in basal ½ of length, width narrowing regularly apicad from ½ of length, apex acute, straight ( Fig. 28D View Fig ).

Sexual dimorphism

Female can be distinguished from males by the rostrum slightly more downcurved in lateral view and with antennae inserted at the apical ⅓ of the length (¼ in males). The elytra of females are also longer (W:L ratio: 0.78–0.83) than those of males (W: L ratio: 0.90).

Life history

This species was collected on male inflorescences of Phoenix reclinata , which probably constitutes the substrate for the larvae. Adults were collected in January, February, March, May and August.

Distribution

In our current knowledge only known from Kenya, Uganda and in the coastal region of the KwaZulu-Natal Province of the Republic of South Africa.

Remarks

In the collection housed at NHMUK, a male specimen from Makindu labelled “ Derelomus bivirgatus Mshl. , Type ♂ ” and bearing a red type label was located. As the description of this species does not refer to a specific type specimen, this male is designated as the lectotype for Derelomus bivirgatus Marshall, 1951 [here designated] and was labelled accordingly. The rest of the specimens were labelled as paralectotypes. Specimens from Kenya and the Republic of South Africa show slight morphological differences, in the latter the rostrum is more downcurved basally in both sexes. These differences are related to regional variation, as observed in other species distributed in Eastern and Southern Africa ( D. fasciatus , D. pallidus , etc).