Meladema lanio (Fabricius, 1775)

Bilton, David T. & Ribera, Ignacio, 2017, A revision of Meladema diving beetles (Coleoptera, Dytiscidae), with the description of a new species from the central Mediterranean based on molecules and morphology, ZooKeys 702, pp. 45-112 : 77-84

Meladema lanio (Fabricius, 1775) Figures 3D, 4D, 5D, 11D, 12D, H, 13D, 14D, 15D, 23, 24B, 26.

Dytiscus lanio Fabricius, 1775: 231.

Colymbetes lowei Gray, 1831: 284.

Scutopterus lanio (Fabricius, 1775): Dejean 1833: 61; Wollaston 1871: 221.

Colymbetes lanio (Fabricius, 1775): Aubé 1838: 221; Wollaston 1854: 82; Wollaston 1865:68.

Meladema lanio (Fabricius, 1775): Sharp 1882: 632; Régimbart 1895: 184; Gschwedntner, 1936: 42; Falkenstöm 1938: 15; Guignot 1961: 770; Balke and Hendrich 1989: 71.

Type locality.

"Maderae aquis"

Type material

(BMNH). Lectotype ♀ (herein designated, Figure 24B): " Dytiscus lanio // Fab. Entom. p. 231. n. 8." [Latin name & 231. n. 8. HW] " Dytiscus lanio // Fabricius, 1775// LECTOTYPE// DT Bilton & I Ribera des. 2017" (dry pinned, BMNH, Banks Collection). Supposed syntypes comprise the above specimen and one other female, located in the Zoological Museum, University of Copenhagen (Zimsen, 1964; A. Solodovnikov, pers. comm.). Sree Selvantharan and Aslak Hansen have kindly communicated a photo of the Copenhagen specimen labelled as lanio (both on its pin, and above it in the cabinet). This is in fact a species of Cybister .

Additional material examined

(genotyped specimens). Portugal, Madeira: 1 ♂ "vi/1998 PORTUGAL Madeira// Ribeira dos Cedros// L. C. Kelly leg." "M3 Hand// Coleoptera " [HW] " Meladema // lanio " [HW] "DNA voucher// NHM-IRM8A" (IBE); 1 ♀ "vi/1998 PORTUGAL Madeira// Levada das Faias// L. C. Kelly leg." "M2 handsearch// Coleoptera " [HW] " Meladema // lanio " [HW] "DNA voucher// NHM-IRM9A" (IBE); 1 ♀ "vi/1998 PORTUGAL Madeira// Levada das Faias// L. C. Kelly leg." "DNA voucher// NHM-IRM9B" (IBE); 1 ♂ "Madeira, Canhas// lado sur de Paul da Serra// 1398 m 32°44'36"N 17°05'56"W // charca sobre arroyo de pietras// 19.7.2011 A. Rudoy leg." "DNA Voucher// IBE-DV298" (IBE). All with " Meladema // lanio (Fabricius, 1775)// D T Bilton [or I Ribera] det. 2017"

Additional material examined

(non-genotyped specimens). Portugal, Madeira: 1 ♀ “pouzo” [HW] "var. squamata" [HW] "passage à la m.// imbricatum Woll." [HW] (ISNB); 1 ♀ "Madeira// 90.32." [HW] (BMNH); 1 ♀ "Madeira// 90.32." [HW] " Colymbetes // lanio // Fabr." [HW] (BMNH); 1 ♀ “Madeira” reverse "48// 99" [small, circular label, HW] " Colymbetes // lanio Fabr.// Madeira" [HW] (BMNH); 1 ♀ “Madeira” reverse "48// 99" [small, circular label, HW] (BMNH); 1 ♂ "Sharp Coll.// 1905-313." " Dytiscus lanio Fab.// ( Scutopterus Woll. Meladema D. S.)// Madeira T. V. Wollaston" [HW] (BMNH); 2 ♂♂, 2 ♀♀ "Madeira// in Fauvel" [HW] "Coll. Odier.// B. M. 1921-288" (BMNH); 3 ♂♂, 3 ♀♀ "MADEIRA// Ribeira da St.// Luzia// 24.VIII.1964// E. W. Classey" [HW] "Brit. Mus.// 1968-48." [8-48 HW] (BMNH); 3 ♂♂, 3 ♀♀ "MADEIRA:// Ribeira de St. Martinho// 13.VIII.1966// E. W. Classey" [HW] "Brit. Mus.// 1966-446" [6-446 HW] (BMNH); 6 ♂♂, 4 ♀♀ "MADEIRA:// Ribeiro de St.// Martinho// 13.VIII.1966// E. W. Classey" [HW] "Brit. Mus.// 1968-48." [8-48 HW] (BMNH); 1 ♂, 2 ♀♀ "MADEIRA:// Ribeira da Abilheira// 19/VIII/1966// E. W. Classey" [HW] (BMNH); 2 ♂♂ "23/iii/1995 MADEIRA// Ribera on 103 below// Poiso & Monte ca.// 900m D. T. Bilton leg." (CBP); 2 ♂♂, 1 ♀ "March 2001 MADEIRA// Levada @ Rabacal// D. T. Bilton leg." (CBP); 1 ♂ "Madeira 1.-4.8.86// 1kn nördl. Poiso// Quellarn d. R. Frio// leg. Balke// Hendrich" "COLL.// HENDRICH// BERLIN" " Meladema // lanio F." [HW] (CBP); 3 ♂♂, 3 ♀♀ "Madeira 8 Anchadas da Cruz// 932 m 32°48'35"N 17°17'47"W // charca de arroyo// 4.07.15 A. Rudoy leg." (IBE); 1 ♂ "Madeira, Canhas// lado sur de Paul da Serra// 1398 m 32°44'36"N 17°05'56"W // charca sobre arroyo de pietras// 19.7.2011 A. Rudoy leg." (IBE); 1 ♂ " lanio Fab." [HW] (BMNH); 1 ♂ "40// 4 2// 2156" [small, circular label, HW] (BMNH); 1 ♂ "40// 4 2// 2157" [small, circular label, HW] "C. Lanio Fabr." (BMNH); 2 ♂♂, 2 ♀♀ without labels (BMNH, Wollaston Collection); 1 ♂ " Meladema // lanio // Fauvel 1897// Madère” [HW] “MUSÉUM PARIS// Coll. P. de Peyerimhoff// 1950" (MNHN); 1 ♂ “MUSÉUM PARIS// Coll. P. de Peyerimhoff// 1950" (MNHN). All with " Meladema lanio // (Fabricius, 1775)// D T Bilton [or I Ribera] det. 2017".

Description

(based on all material examined).Size: Lectotype TL = 20.30 mm; EL = 16.30 mm; MW = 10.18 mm. Other material examined TL = 17.40-21.12 mm; EL = 12.67-15.36 mm; MW = 8.70-10.50 mm.

Colour. Dorsum (Figure 3D), dark reddish brown to yellow. Labrum yellowish, red anterolaterally in some specimens; clypeus yellowish except central ca. 1/6 red to blackish, connected to dark pigmentation on frons. Frons with transverse pale strip anterolaterally, adjacent to pale parts of clypeus, otherwise dark reddish brown. Me dial, paired interocular patches on frons yellow; strongly transverse apicolaterally, almost reaching channel around interior margin of compound eye; confluent in centre in some specimens. Pronotum dark reddish brown on disc; narrowly reddish along anterior margin; lateral margins broadly yellowish. Elytra yellowish brown to greenish brown, with black irrorations; pattern visible without being lifted, but more evident when done so (Figures 3D, 4D). Legs yellowish brown to black; posterior tibiae and tarsi darkest. Antennae and maxillary and labial palpi yellowish to reddish. Venter reddish brown; prementum yellow; posterior genae, mentum and submentum reddish. Pronotal hypomeron and shoulder and outer portion of elytral epipleurs yellowish.

Head. Labrum shining, with medium to fine, sparse punctures. Reticulation absent anteriorly, clearly evident in posterior half, here fine and composed of small, isodiametric to transverse meshes. Clypeus weakly shining, with medium to fine, sparse punctures and traces of very fine, shallow, close punctures. Frons weakly shining, entire surface with, open reticulation; weak in front of interocular patches, becoming stronger and more evident posteriorly. Meshes transverse to isodiametric apically and medially, strongly elongate posteriorly and onto vertex. Paired epicranial foveae on anterior frons, one immediately behind the other. Anterior foveae transverse, posterior foveae elongate oval. Foveae reticulate; anterior and posterior foveae linked by reticulated channel. Internal and posterior borders of compound eyes distinct, raised relative to level of adjacent cuticle. Lateral margins bordered by distinct narrow chan nel; deeper anteriorly than posteriorly and continuing behind posterior margin of eye onto vertex. Channel with dense punctures, bearing long, stiff, yellow recumbent to decumbent setae.

Pronotum. Posterior margin weakly sinuate laterally (Figure 3D). Surface somewhat shining, strongly rugose. Reticulation meshes large, open, flat and with varying sizes and orientations. Transverse irregular row of medium punctures bearing long, yellow recumbent to decumbent setae 1/5 behind anterior pronotal margin; interrupted briefly in centre, obscured by reticulation inside lateral margins but continuing inside lateral third of posterior margin. Reticulation weak and obsolete anterior to transverse row, surface here clearly double punctate, with very fine, dense and medium, sparse to very sparse punctures. Scattered medium punctures visible elsewhere, amongst meshes of microreticulation. Centre of disc with elongate, narrow, slit-like fovea, partly obscured by reticulation in some specimens, but then traceable as an elongate reticulation channel. Lateral margins slightly raised, shining, without rugose sculpture and with fine, scattered punctures.

Elytra. Shining, without crescentic striolae (except in some females - see below). Surface doubly punctate and reticulate (Figure 5D); with very fine, close and fine to medium, sparse punctures (the latter bearing short, peg-like setae). Reticulation fine, somewhat obsolete, meshes isodiametric; sometimes obscuring very fine punctation. Surface weakly tuberculate towards sides and apex, particularly in posterior third (see Figure 3D). Puncture rows well-marked, continuous almost to elytral apices; punctures shallower posteriorly than anteriorly.

Venter. Prementum shining, tumid in centre, with fine and medium, sparse punctures. Mentum shining; central projection with shallow median emargination. Lateral lobes with medium, sparse punctures, and scattered, whitish recumbent to decumbent setae. Submentum shining, with transverse wrinkles centrally, and elongate wrinkles laterally. Central 1/4 with medium, sparse punctures bearing long, white-yellowish, erect setae. Gula shining, with sparse, shallow, transverse wrinkles; patch of medium-coarse punctures posterolaterally. Genae shining, with obsolete, open, elongate reticu lation. Prosternum shining, with weak, low, irregular transverse ridges laterally. Arched in centre and with fine, moderate to close punctures laterally, bearing long, white-yellowish, recumbent to erect setae; punctures and setae extending in an irregular row onto process, just below arch. Process lanceolate, arched; apex acuminately rounded. Centre of prosternum and process with double punctation of very fine, close to very close and medium, sparse to moderate punctures. Pronotal hypomeron shining, impunctate. Elytral epipleurs shining, with fine wrinkles; irregular puncture row close to internal margin, from centre to close to apex, punctures bearing fine, whitish, erect setae. Metaventrite shining, central portion with reticulation reduced to sparse, transverse scratches and very fine, close and fine to medium, sparse punctures. Metaventral process strongly reticulate, with transverse to elongate, rugose meshes and traces of fine, sparse punctures. Metaventral process relatively broad; apex acuminate and upturned slightly anterolaterally. Metacoxal lines not reaching anterior border of metacoxae, disappearing approx 1/10 from margin. Internal laminae of metacoxae shining, sculpture as on centre of metaventrite. Metacoxal lobes sculptured as internal laminae, strongly rounded, with irregular, elongate field of medium to coarse punctures close to lateral margins, bearing fine, white, recumbent to erect setae. External laminae of metacoxae shining, smooth close to process, and with obsolete reticulation elsewhere; without distinct meshes, wrinkled, elongate around anterior and posterior margins; doubly ounctate, with very fine, close and fine, very sparse punctures. Abdominal ventrites shining. Ventrites 3-5 with cluster of golden, erect setae anteromedially. Ventrite 1 with weak reticulation of elongate scratches throughout. Ventrite 2 with similar reticulation; absent close to centre. Ventrite 3 and 4 with scratches restricted to lateral 1/3. Ventrites 2-5 doubly punctate; very fine, moderate and fine, sparse to very sparse punctures; punctures most evident in areas without reticulation. Ventrites 3-5 with transverse irregular row of long, yellowish, recumbent to decumbent setae laterally. Ventrite 6 (Figure 11D) with very fine, moderate punctures and medium to coarse, sparse to moderate punctures; punctures coarser close to apex. Elongate, semicircular wrinkles and channels apicolaterally and centrally; apicolateral sculpture extending basally around central portion of ventrite. Some punctures in channels bearing elongate, whitish, erect setae.

Male. Foretarsi (Figure 12D) with articulo-setal counts as follows (base to apex): row 1, 8-9; row 2, 10; row 3, 10; row 4, 8. Number of setae in rows may differ from right to left tarsus in same beetle. Curved, golden setae bordering articulo-setal field relatively sparse, particularly laterally. Foretarsal claws (Figures 12D, 13D) elongate, curved. Mesotarsi (Figure 12H) with articulo-setal counts as follows (base to apex): row 1, 7-8; row 2, 8; row 3, 8; row 4, 6 (2 clusters of 3, situated laterally). Curved, golden setae bordering articulo-setal field relatively sparse, especially laterally. Mesotarsal claws (Figure 12H) elongate, curved. Abdominal ventrite 6 (Figure 11D) with apex rounded, with well-marked median emargination. Median lobe (Figure 14D) asymmetrical, sinuation strong, approximately 1/3-0.35 from apex; ventral margin of apical portion relatively straight in lateral view. Parameres (Figure 14D) with inner margin almost right-angled at base, with distinct small projection; outer margin undulated slightly; inner straight.

Female. As male, except for simple fore and mesotarsi, and differently shaped abdominal ventrite 6 (with bluntly pointed apex - Figure 15D).

Variation. Males and females generally have identical sculpture on the elytra. Two females studied, one from Ribeira da St. Luzia (Figure 26B, BMNH) and one from “pouzo” (ISNB) have distinct crescentic striolae, as have been observed in female M. imbricata from La Palma (see above). Females sculptured in this manner appear to be relatively rare, the only other occurrences of this form we can find being mentioned by Aubé (1838), who had seen a female with this sculpture (see also Sharp 1882) and Falkenström (1938). Such females may be mistaken for M. imbricata , as was the case with the ISNB animal listed above.

Differential diagnosis.

Closest to M. imbricata ; for diagnostic characters see under that species.

Distribution.

Restricted to the main island of Madeira (Figure 23), where it is relatively widely distributed in permanent streams, particularly in remnant laurel forests in the mountains. Can also be found in man-made levada systems. Much more abundant on Madeira than M. imbricata on the Canaries, but still listed as Vulnerable (B1 + 2b) on the IUCN Red List ( Foster 1996b), reflecting its very small global range.