Metriorrhynchus lineatus Kirsch, 1875

Bocak, Ladislav, 2007, A Revision Of Metriorrhynchus (Coleoptera: Lycidae) From The Greater Sunda Islands And Continental Asia, Raffles Bulletin of Zoology 55 (2), pp. 253-260 : 256-257

Metriorrhynchus lineatus Kirsch, 1875

(Figs. 10–11)

Dictyopterus lineatus Kirsch, 1875: 35 .

Metriorrhynchus lineatus – Waterhouse, 1879: 50; Kleine, 1933: 81.

Metriorrhynchus kirschii Waterhouse, 1879: 50 (a junior objective synonym).

Metriorrhynchus enganoensis Pic, 1921: 11 ; Kleine, 1933: 81; transferred from the synonymy of M. inaequalis .

Metriorrhynchus enganicus Kleine, 1939: 5 , new synonym.

Metriorrhynchus regularis Pic, 1921: 11 , new synonym.

Metriorrhynchus dives Kleine, 1926: 310 , new synonym.

Material examined. – Metriorrhynchus lineatus : male, holotype ( SMTD), Malacca .

Metriorrhynchus enganoensis : female, holotype ( MHNP), Engano, Kila-juc. V. Modigliani, 1891 .

Metriorrhynchus regularis : female, holotype ( MHNP), Ins. Nias. Metriorrhynchus dives : male, holotype ( BMNH), Quop, W. Sarawak, G. E. Bryant, G. E. Bryant coll. 1919–147, Mar.–Apr.1914 .

Metriorrhynchus enganicus : female, paratype ( MIZW), Enggano.

Others: 1 male, 1 female ( LMBC), S. Thailand, Ranong, native coll., Feb.1989; 1 male ( LMBC), Sumatra, Aceh , 15 km SSE Takengon, 1,600 m, L. Bocak coll. , 26 Feb.–13 Mar.1998; 1 male ( BMNH), [Sumatra] Marang, Res. Bengkoelen (coll. Doherty); 1 female ( BMNH), Siberut Island, West Sumatra , C. B. K. and N. S coll ., Sep.1924; 1 male ( BMNH), Ins. Engano, Res. Bengkoelen (coll. Doherty); 1 male ( LMBC), Sumatra , SW coast of Ranau lake , 1,200 m, coll. Bolm , 1–4 Jun.2001; 1 male, 1 female ( LMBC), Sumatra, Liwa , coll. L. Dembicky , 2003; 4 males, 1 female ( LMBC), S. Kalimantan Prov. , 10 km E of Loksado, 600–1,100 m, 2°43'57"S 115°32'50"E, coll. Bolm , 18–23 Jun.2001; 1 male ( LMBC), C Kalimantan Prov. , 60 km SE Muara Teweh, 150 m, 1°20'25"S 115°20'16"E, coll. Bolm , 24–28 Jun.2001; 1 female ( LMBC), Malaysia, W Johor, 20 km S of Mersing, Jemaluang , coll. P. Cechovsky , 1–14 Feb.2003; 1 male ( LMBC), Perak, coll. Doherty ; 1 male (the specimen identified by C. O. Waterhouse as M. kirschii ) ( BMNH), Sing.; 1 male ( BMNH), Malay States, Bukit Kutu , 3,300 feet (ca. 1,006 m), A. R. Sanderson , Apr.1929; 1 male, 8 females ( BMNH), Sumatra, Engano Is. , coll. Doherty.

Differential diagnosis. – Metriorrhynchus lineatus is very similar to M. inaequalis and these species cannot be distinguished by colouration and external morphology. Only male and female genitalia provide sufficient diagnostic characters (Figs. 1–2, 9–11).

Redescription. – For external morphology and colouration see the above description of M. inaequalis . Male and female genitalia as in Figs. 10, 11.

Measurements. – Body length 7.6–14.1 mm, width at humeri 2.1–3.3 mm.

Distribution. – Peninsular Malaysia, Thailand south of the Isthmus of Kra, Sumatra, Borneo, Enggano, Siberut and Nias Islands.

Variability. – Metriorrhynchus lineatus forms mimicry rings with M. inaequalis as stated above. Only M. lineatus occurs in the Siberut and Enggano Islands and it has a black pronotum similar to specimens from Borneo but unlike the populations from the adjacent coast of Sumatra. A specimen from the Nias Island resembled the Sumatran populations in colour pattern.

Remarks. – Waterhouse (1879) proposed Metriorrhynchus kirschii as a new name for Dictyopterus lineatus Kirsch, 1875 . He classified Omalysus lineatus Hope, 1831 in Metriorrhynchus and therefore considered D. lineatus to be a junior secondary homonym in the genus Metriorrhynchus . Kleine (1933) classified O. lineatus in Cautires and he considered both M. lineatus and M. kirschii to be junior synonyms of M. inaequalis . The two sympatrically occurring Metriorrhynchus species in the Greater Sunda Islands are now recognized as valid and M. lineatus is removed from the synonymy.

I have also found that M. dives , M. enganicus and M. regularis are conspecific with M. lineatus . Metriorrhynchus enganoensis was put in synonymy of M. inaequalis by Kleine (1933), but it is in fact a junior subjective synonym of M. lineatus .

The extensive synonymy in the M. inaequalis group is a consequence of the geographically dependent polymorphism of both M. lineatus and M. inaequalis . The populations of both species from different islands and mountain ranges differ in the colouration of the pronotum or the extent of bright colouration of the elytra (e. g. both species have black pronotum in Borneo and red pronotum in Sumatra). The older authors defined their species typologically and described the various mimicry types as species. Waterhouse (1879) speculated on the difference in the strength of elytral costae between M. inaequalis and M. lineatus , but this character is partly dependent on mimicry ring membership and also on the size of the individual. Only Kleine included male genitalia in his species definitions, but he usually dissected only the holotypes and he did not discover the presence of two species in the same area and considered most of them to be synonyms of M. inaequalis . These species are so similar that only specimens collected in copula enabled the association of conspecific males and females.