Dematochroma difficilis Heller 1916
Creators: name: Gómez-Zurita, Jesús
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Dematochroma
Dematochroma difficilis

description: Dematochroma difficilis (Heller, 1916), status revived
(Figs 7, 16–19, 23)
Thasycles difficilis Heller, 1916:305.
Dematochroma difficilis: Jolivet et al., 2007a:39 (as synonym of D. terastiomerus).
Type material. Province Nord: Holotype, 13 (Fig. 7): Tao, 24 June 1911, F. Sarasin & J. Roux leg. [pale blue label], 1915/18 [pale blue label], difficilis Typus [red label] (MfT).
Other material examined. Province Nord: 33, 3Ƥ: Bopope, 20.91730ºS 165.06317ºE 115m, 8 April 2008, J. Gómez-Zurita & J.A. Jurado-Rivera leg. (IBE-JGZ); 23, 4Ƥ: Col des Roussettes, 21.41455ºS 165.47198ºE 558m, 19 March 2008, J. Gómez-Zurita & A. Cardoso leg. (IBE-JGZ); 13, 4Ƥ: Baie Ugué, 21.15543ºS 165.54190ºE 8m, 30 March 2008, J. Gómez-Zurita, J.A. Jurado-Rivera & A. Cardoso leg. (IBE-JGZ); 13, 1Ƥ: Ouégoa, Mandjélia, 20.39683ºS 164.53218ºE, 787m, 7–8 February 2005, S. Cazères & C. Mille leg. (SRFP); 13, 1Ƥ: Poindimié, 3 February 1977, J. Balogh leg. (HNHM); 2Ƥ: Caavatch (= Kaavac), 5 February 1977, J. Balogh leg. (HNHM); 13: Ponérihouen, Mt. Ounda, 700m, 11 October 1969, J. Balogh leg. (HNHM). Province Sud: 33, 3Ƥ: Moméa, 21.65498ºS 166.63797ºE 154m, 14 April 2008, J. Gómez-Zurita, J.A. Jurado-Rivera & A. Cardoso leg. (IBE-JGZ); 13, 4Ƥ: Col d’Amieu 21.61172ºS 165.80805ºE 489m, 21 March 2008, J. Gómez-Zurita & A. Cardoso leg. (IBE- JGZ); 83, 9Ƥ: Col d’Amieu 21.61172ºS 165.80805ºE 489m, 7–8 March 2008, J. Gómez-Zurita, J.A. Jurado-Rivera & A. Cardoso leg. (IBE-JGZ); 2Ƥ: Col d’Amieu, 21º34.922’S 165º46.324’E 630m, 13 March 2008, J. Gómez- Zurita, J.A. Jurado-Rivera & A. Cardoso leg. (IBE-JGZ); 13: Col d’Amieu, 21º34.922’S 165º46.324’E 630m, 11 March 2008, J. Gómez-Zurita, J.A. Jurado-Rivera & A. Cardoso leg. (IBE-JGZ); 1Ƥ: Sarraméa, Col d’Amieu, 2– 25 November 2005, S. Cazères, C. Mille & J.-P. Kataoui leg. (IBE-JGZ); 23, 2Ƥ: Thio, Ouroué, 21.58892ºS 166.19388ºE 10m, 9 March 2008, J. Gómez-Zurita, J.A. Jurado-Rivera & A. Cardoso leg. (IBE-JGZ); 43, 1Ƥ: Thio, hour sign 21º35’284S 166º09’078E 26m, 29 March 2008, A. Cardoso & J.A. Jurado-Rivera leg. (IBE-JGZ); 13, 3Ƥ: ca. Table Unio, 21.59633ºS 165.65570ºE 47m, 14 March 2008, J. Gómez-Zurita, J.A. Jurado-Rivera & A. Cardoso leg. (IBE-JGZ); 133, 13Ƥ: Sarraméa, 21.67005ºS 165.80852ºE 37m, 13 March 2008, J. Gómez-Zurita, J.A. Jurado-Rivera & A. Cardoso leg. (IBE-JGZ); 1Ƥ: Farino (refuge), 21.64877ºS 165.78077ºE 261m, 27–28 March 2008, J. Gómez-Zurita, J.A. Jurado-Rivera & A. Cardoso leg. (IBE-JGZ); 13: ca. Farino, 21.61288ºS 165.70209ºE 384m, 11 April 2008, J. Gómez-Zurita, J.A. Jurado-Rivera & A. Cardoso leg. (IBE-JGZ); 23, 2Ƥ: ca. Farino, 21.62402ºS 165.70852ºE 290m, 11 April 2008, J. Gómez-Zurita, J.A. Jurado-Rivera & A. Cardoso leg. (IBE-JGZ).
The original description of this taxon was based on an unspecified number of males from Tao, in the northeastern coast of Grande Terre. The collection at MfT holds a single male specimen matching Heller's (1916) description and collection data, with a manuscript type label presumably by K.H. Heller. This specimen is regarded here as the holotype, by monotypy. The large number of specimens of either sex available for this study is used to complement the original diagnosis of the species with a description of the female, as well as both male and female genitalia.
Female: Length: 5.2–5.8mm, width: 2.6–2.9mm. Body elongated, uniform orange pale brown, except blackened apex of mandibles. Females slightly darker compared to males, in some cases brown, or more rarely with dark brown elytra and blackish head and pronotum, as in the case of two females, one each from Col d’Amieu and Thio.
Surface of head nearly smooth, shining, more or less uniformly covered by sparse small punctures, with very short, fine translucent setae near eyes. Eyes large, convex, dorso-ventrally elongated, weakly emarginated at inner margin. Clypeus bell-shaped, continuing frontal slope, but slightly depressed at apex towards apical, evenly concave emargination; surface smooth, shiny, impressed with punctures at basal half. Labrum subrectangular, slightly broader than apical emargination of clypeus; anterior angles regularly curved and anterior border feebly emarginated. Antennae fine and slender, thinner than male antennae, reaching basal third of elytra; second antennomere elongated, slightly club-shaped; third elongated, longer than second, weakly expanding towards apex; antennomeres 4–6 elongated, thin, fifth longest; antennomeres 7–10 progressively elongated, slightly broader than previous, alutaceous, seventh longest and more conspicuously widened apically; last antennomere as long as previous, pointed apically.
Pronotum transverse, 1.8x wider than long at middle, convex, with anterior angles sloping downwards; anterior border weakly convex, finely margined; posterior border regularly convex, with slightly elevated margin, broader than anterior margin; sides evenly and strongly curved, widest at middle, with wide, explanate, shiny margin, internally marked by row of tight punctures; anterior angles slightly protruding forward at short distance on anterior border, with setigerous pore at apex; posterior angles laterally protruding as small teeth, with setigerous pore at apex; surface finely alutaceous, densely and uniformly punctured except near borders with punctures stronger than those on vertex and frons. Prosternum narrow before procoxae; prosternal process as broad as procoxae, strongly widened at apex, enclosing procoxal cavities behind, connecting with basal border of hypomera; process slightly concave apically, following contour of prothoracic base. Hypomera finely alutaceous, with dark punctures concentrated near anterior angle and posterior margin.
Scutellum wider than long, broadly curved at apex, with few small punctures near base. Elytra elongated, parallel-sided up to middle and progressively tapering towards curved apex; surface finely alutaceous, densely covered by punctures, stronger than pronotal punctures, heterogeneous in size, finer on disc, near base and apical declivity, and coarser, stronger and deeper on lateral declivities; primary punctures forming longitudinal arrangements on disc in sutural area and premarginally (both series regularly meeting at elytral apex), and transversal or oblique arrangements laterally on disc in posthumeral area. Humeri short, strongly callose, shiny, unpunctured; longitudinal interstices at lateral declivities feebly raised as two longitudinal costae. Apical longitudinal convexity of elytra abruptly curved vertically before apex; fine, short, semierect golden setae in this area, below second premarginal striae of punctures; female pubescence at apex of elytra denser than in males. Epipleura sloping downwards, visible laterally in entire length, narrowing gradually and disappearing before apical curvature of elytra.
Mesanepisterna very finely alutaceous, unpunctured; metanepisterna leathery, with shallow punctures anteriorly and near external margin, and very fine, short translucent setae. Metaventrite finely alutaceous, with sparse, fine punctures and fine whitish setae, particularly near anterior angles. Femora spindle-shaped, broader near middle, alutaceous, sparsely uniformly pubescent with semierect whitish setae; profemora only pubescent dorsally with shorter setae. Tibiae straight; mesotibiae proportionally slightly shorter; external longitudinal edges weakly raised as longitudinal keels from base to apex, delimiting laterally at apex space for tarsal insertion; ordered fringes of semierect translucent setae arranged close to tibial edges; outer edge of meso- and metatibiae slightly emarginated preapically, with short acute apical tooth. Tarsi narrow, elongated; first tarsomere narrowest, subtriangular, elongated, particularly in metatarsi; second subtriangular, with concave apical emargination dorsally, at insertion of third, deeply bilobed tarsomere; fifth twice as long as third; claws strongly divaricate, appendiculated. Abdominal ventrites alutaceous, finely punctured, with sparse semierect fine white setae; first ventrite with broad, nearly semicircular anterior intercoxal process; third and fourth progressively concave apically; fourth accommodating slightly raised apical biconcave emargination of fifth ventrite. Pygidium with dorsal broad longitudinal furrow.
Genitalia: The penis (Figs 16–19) of this species is very characteristic, slender and elongated, regularly curved in lateral view before strongly modified apex; slightly widened laterally in this region, basal to modified apical area, where ostium opens dorsally. Ventral concavity bent perpendicularly to basal axis at level with apex of ostium; apical area expanded as subrectangular, transversely concave plate; apical expansion with dorsal median prominence; apex curved, margined; ostium opening at wide obtuse angle right below slight lateral enlargement of penis with contour following lateral widening of penis, enlarging at basal 1/3 and gradually narrowing at apical 2/3 as elongated isosceles triangle with blunt apex reaching median dorsal prominence of apical expansion. Spermatheca (Fig. 23) stout, with pump beak-shaped, broadly connected to bulbous receptacle at acute angle; spermathecal duct very thin, with short sclerotized distal part, joining receptacle prebasally and internally; spermathecal gland attached to receptacle shortly below junction of spermathecal duct.
Remarks. Jolivet et al. (2007a), after examining the same type material studied here, proposed sthe ynonymy of D. difficilis with D. terastiomerus (Heller). These two species are similar externally, with roughly the same size, elongated shape and yellowish coloration, and usually collected in the same places. However, a simple visual inspection of external morphology reveals numerous conspicuous differences, including the strongly developed and corrugated femora characteristic of male D. terastiomerus as opposed to normal spindle-shaped femora of D. difficilis, differences which are persuasively corroborated by completely different male and female genitalia (see Figs 16–19, 21, 23, 31–33). Note that the penis figured in Jolivet et al. (2007a) as belonging to D. terastiomerus (Jolivet et al. 2007a: Figs 15–16) does not match either this species or D. difficilis, while the spermatheca (Jolivet et al. 2007a: Fig. 17) may actually correspond to this species. These species also differ externally by: (1) D. terastiomerus more convex than D. difficilis; (2) frons with darkened longitudinal furrow in D. terastiomerus, weakly developed in D. difficilis; (3) male antennae thicker in D. terastiomerus; (4) second antennomere elongated, slightly shorter than third in D. difficilis, globose and much shorter than third in D. terastiomerus; (5) pronotum of D. terastiomerus less transverse and its sides less convex, with narrower margin; (6) pronotal angles in D. terastiomerus weakly or not protruding; (7) pronotal puncturation finer in D. terastiomerus; (8) prosternal process broad, subrectangular in D. terastiomerus and narrower, gradually expanding apically in D. difficilis; (9) hypomera strongly and sparsely punctured basally in D. difficilis, nearly impunctate in D. terastiomerus; (10) females of D. difficilis with longitudinal costae laterally on elytra, absent in D. terastiomerus; (11) transversal arrangements of elytral punctures in D. difficilis not apparent in D. terastiomerus; (12) entirely glabrous apex of elytra in D. terastiomerus, nearly always with short whitish setae in D. difficilis (only lacking in a few males); (13) anterior process of first abdominal ventrite narrow, triangular between coxae in D. terastiomerus, but broad, nearly semicircular in D. difficilis; (14) apical emargination of female last abdominal ventrite regularly concave in D. terastiomerus or with median pointed projection in D. difficilis. In summary, D. difficilis (stat. rev.) is a valid species, very different from D. terastiomerus.
Distribution. Dematochroma difficilis appears distributed throughout most of the Grande Terre, including many of the same places where D. terastiomerus (Heller) was collected, sometimes on the same plants. However, in contrast to the latter species, it shows a greater altitudinal range, from sea level in localities like Ouroué up to 787m in Mandjélia.
description: Published as part of Gómez-Zurita, Jesús, 2011, Revision of New Caledonian species of Eumolpinae described by K. M. Heller (Coleoptera: Chrysomelidae), pp. 31-46 in Zootaxa 3060 on pages 37-39, DOI: 10.5281/zenodo.205363