Longitarsus doeberli Biondi & Alessandro 2017, sp. nov.

Longitarsus doeberli sp. nov.

(Figs 2, 4–7, 9, 12–13)

Type locality. Yemen, Socotra Island, Dixam plateau, Tudhen.

Type material. HOLOTYPE: J, ‘ YEMEN, Socotra Island / Dixam plateau, Tudhen / shrubland with Commiphora planifrons, 18.+ 22.vi.2012 / 12° 32.7’N, 53° 53.9’E, 1135 m // Socotra expedition 2012 / J. Bezděk, J. Hájek, V. Hula, / P. Kment, I. Malenovský, / J. Niedobová & L. Purchart leg. // Holotypus J / Longitarsus doeberli n. sp. / M. Biondi & P. D’Alessandro det. 2017’ [red label]. PARATYPES: 1 J and 2 ♀♀, same data as the holotype, each with a red label ‘ Paratypus / Longitarsus doeberli n. sp. / M. Biondi & P. D’Alessandro det. 2017’.

Description of male holotype. Dorsal integument black, more reddish on pronotum, with evident metallic reflection. Body (Fig. 2) compact, sub-oval (LB = 1.74 mm), rather convex. Maximum pronotal width in middle: 0.72 mm; maximum elytral width in basal third: 0.95 mm.

Head (Fig. 4) with impunctate vertex and frons but with some weakly impressed and large punctures near frontal grooves; surface wrinkled and sparsely punctuated between eyes. Frontal tubercles finely delimited, elongate, sub-horizontal, with smooth surface; frontal grooves finely impressed, distally convergent to ocular margin; frontal carina wide, not raised; labrum elongate, sub-trapezoidal, blackened; palpi distinctly darkened; eyes sub-elliptical, not reduced; antennae elongate (LAN = 1.42 mm; LAN/(LE+LP) = 0.84) with yellowish antennomeres I–V and gradually darkened antennomeres VI–XI; length of each antennomere of right antenna proportional to numerical sequence 18: 8: 8: 10: 14: 12: 18: 13: 14: 14: 18 (1 = 0.01 mm).

Pronotum (Figs 2, 5) scarcely transverse (LP = 0.56 mm; WP/LP = 1.29), laterally distinctly rounded, basally slightly narrower; lateral and basal margin very finely bordered; punctation evenly distributed with moderately densely impressed punctures on smooth surface. Scutellum wide, semi-circular, with smooth surface.

Elytra elongate (Fig. 2) (LE = 1.12 mm; LE/LP = 2.00) but not covering pygidium completely, laterally distinctly rounded, apically widely arcuate, apparently sub-truncate in dorsal view; punctation (Fig. 5) similar to that on pronotum but more strongly impressed, very homogenous, with large punctures impressed on smooth surface; humeral calli and metathoracic wings absent.

Fore and middle legs entirely yellowish; hind legs with femora darkened; distal two thirds of metatibiae distinctly dentate on external edge (Fig. 7); apical spur of metatibiae about as long as tibial apex width; protarsomere I (Fig. 6) and mesotarsomere I slightly but distinctly enlarged; metatarsomere I (Fig. 7) shorter than half metatibial length (LFMT/LHT = 0.44). Ventral parts dark brown, with paler abdomen; apical ventrite without preapical dimples or impressions.

Median lobe of aedeagus (Fig. 9) (LAED = 0.79 mm; LE/LAED = 1.41) moderately elongate; in ventral view laterally slightly tapered from base to apical fifth; distal part sub-lanceolate without any median small tooth apically; ventral sulcus elongate, deeply impressed, gradually narrowing from apex towards basal part, basally not interrupted; dorsal sulcus U-shaped, apical fourth visible; dorsal ligula apically sub-rectangular; in lateral view basal half of median lobe slightly curved and distal half widely and slightly sinuous.

Variation. Paratypes very similar in shape, sculpture and colour to the holotype but sometimes with more darkened metafemora. Females with slightly shorter antennae and not enlarged first protarsomere and mesotarsomere. Spermatheca (Figs 12–13) with sub-reniform basal part; distal part developed, not well distinct from collum; ductus very elongate, simple or with a strict semi-coil, basally and medially inserted.

Measurements. ♂ (n = 1): LE = 1.16 mm; LP = 0.56 mm; WE = 1.00 mm; WP = 0.74 mm; LAN = 1.48 mm; LAED = 0.82 mm; LB = 1.90 mm; LE/LP = 2.07; LE/WE = 1.16; WP/LP = 1.32; LE/LAED = 1.41; LAN/(LE+LP) = 0.86. ♀ (n = 2): LE = 1.26, 1.26 mm; WE = 1.00, 1.06 mm; LP = 0.51, 0.52 mm; WP = 0.68, 0.70 mm; LAN = 1.28, 1.34 mm; LSP = 0.45, 0.38 mm; LB = 1.88, 1.94 mm; LE/LP = 2.47, 2.42; LE/WE = 1.26, 1.19; WP/LP = 1.33, 1.35; LE/LSP = 2.80, 3.32; LAN/(LE+LP) = 0.72, 0.75.

Differential diagnosis. Based on the body colour, wing reduction, the shape of the median lobe of aedeagus and the spermatheca, Longitarsus doeberli sp. nov. could be attributed to the subgenus Testergus Weise, 1893. However, in our opinion the real affiliation of this taxon still needs further investigation, considering also the different meanings given to it by recent authors (KONSTANTINOV 2005, DÖBERL 2010). Based on the external habitus, the new species seems very similar to Longitarsus lederi Weise, 1889 (Figs 2–3), but this similarity is only superficial and due to adaptive convergence to isolated environments with trend of loss of flying ability and, to a lesser extent, jumping abilities. In fact, considering the morphology of the median lobe of aedeagus (Figs 9–10), and the spermatheca (Figs 12–14), these two species are clearly different. Based on the shape of the aedeagus and mostly the peculiar spermatheca with long and widely arcuate ductus (Figs 12–13), Longitarsus doeberli sp. nov. indeed shows closer affinity to the species of the L. anchusae group (sensu BIONDI 1995), especially L. anchusae (Paykull, 1799) and L. anatolicus Weise, 1900, widespread mainly in Southern Europe and Western Asia (Figs 1, 8, 11). However, the new species can be easily separated from them by the following characters: body clearly thicker; pronotum wider; metatarsomere I shorter; median lobe of aedeagus less slender and distally not lanceolate, with wider ventral sulcus; spermatheca smaller, with distal part shorter not well distinct from collum.

Etymology. The name of the new species is dedicated to our friend Manfred Döberl, an excellent specialist in flea beetles who recently passed away.

Habitat. All specimens were collected on the type locality Tudhen with vegetation dominated by Juncus socotranus (Juncaceae), Cyperus sp. (Cyperaceae), Bacopa monieri (Plantaginaceae) and Exacum caeruleum (Gentianaceae). The area was grazed by cattle and situated within an extensive sparse montane shrubland dominated by Commiphora planifrons, Cephalocroton socotranus, Croton sulcifructus, and Croton socotranus.

Comments. Longitarsus doeberli sp. nov. shows a complete reduction of the metathoracic wings, so it is not able to fly, which limits its accidental removal from its insular habitat. Moreover, considering that Longitarsus species perform in jumping better than Aphthona species (cf. SCHMITT 2004, NADEIN & BETZ 2016), reduction in length of the first metatarsomere in the new species is likely to result in a lower jumping ability, thus further limiting the movement. Considering the clear relationships of L. doeberli sp. nov. with the species of the Longitarsus anchusae group, we presume that it is very probably associated with the plant family Boraginaceae.

Distribution. Species endemic to Socotra Island.