Oulema melanopus
Creators: name: Bezděk, Jan
name: Baselga, Andrés
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Oulema
Oulema melanopus

description: Taxonomy of the Oulema melanopus species group
Given the extreme similarity among species belonging to the O. melanopus species-group, we provide a general description first, and then specific diagnoses for previously described species, and detailed descriptions for new species.
Species included. Oulema duftschmidi (Redtenbacher, 1874), O. melanopus (Linnaeus, 1758), O. rufocyanea (Suffrian, 1847), O. mauroi sp. nov., O. verae sp. nov., and eastern Palaearctic O. oryzae (Kuwayama, 1931).
Description. Male. Colouration (Figs 1–5). Head dark metallic blue, antennae black with antennomeres I and II dark metallic blue. Pronotum orange-red, anterior and posterior margins sometimes thinly black. Scutellum and elytra metallic blue to black. Meso-, metathorax and abdominal ventrites metallic blue to metallic black. Legs: coxae, trochanters, tarsi and apices of tibiae black, femora and tibiae orange.
Body moderately flat, parallel, glabrous, lustrous.
Head. Frontoclypeus triangular, punctate and covered with setae, anterior margin more or less straight; frontal tubercles not elevated, smooth, glabrous; frontal grooves very deep, V-shaped, frons covered with large punctures, each bearing long pale seta; vertex covered with small punctures, almost glabrous, with distinct median line. Antennae slender, 0.45–0.61 times as long as body, antennomere I bulbous, antennomere II smallest, almost as wide as long (Figs 11–15).
Pronotum quadratic or subquadratic (Figs 6–10), widest at midlength or just before midlength, convex, lustrous. Surface shallowly constricted before base. Disc covered with sparse large punctures, basal constriction and area around posterior corners usually covered with very small dense punctures. Anterior margin thinly bordered, lateral margins almost parallel to widely rounded, unbordered, in posterior half always convergent, posterior margin slightly rounded, thinly bordered. Anterior angles more or less rectangular with swollen tip, posterior ones only slightly indicated. All angles bearing setigerous pore with erect long pale seta.
Scutellum trapezoidal, ca. as wide as long, lateral margins slightly convergent, posterior margin slightly concave, straight or slightly rounded, surface glabrous, impunctate.
Elytra moderately flat, 1.69–2.05 times as long as wide at humeral part, glabrous, lustrous, covered with 10 striae composed of large deep punctures (smaller and shallower near basal margin and in apical area) and short scutellar stria composed of 4–6 small shallow punctures; distance between punctures on elytral disc ca. as wide as diameter of puncture. Humeral calli well developed, impunctate. Epipleura very narrow, disappearing towards apex.
Legs. Femora lustrous, moderately covered with pale setae. Tibiae slender, slightly tapering basally, covered with dense pubescence, outer side on basal half nearly glabrous, apices armed with pair of short, subequal, black-brown spines ventrally.
Tarsi relatively slender. Tarsomeres I elongate triangular, shorter than two following tarsomeres combined, tarsomeres II triangular. Claws simple.
Ventral part. Prosternal projection not visible between procoxae. Mesoventrite densely covered with small punctures bearing pale setae, mesoventral process wide, separating mesocoxae, ca. 0.5 times as wide as diameter of mesocoxa. Metaventrite laterally and anteriorly subopaque, covered with large punctures bearing pale setae; medially and towards posterior margin lustrous, nearly impunctate; medially at posterior quarter with impressed line; posterior margin shallowly incised in middle. Abdominal ventrites lustrous, uniformly covered with small punctures bearing pale setae; ventrite I twice as long as II and III combined, ventrite V 1.5 time as long as IV.
Male genitalia. Aedeagus of relatively uniform structure, but with specific internal sclerite (flagellum) posessing short posterobasal arms (Figs 16–23).
Female. Sexual dimorphism indistinct. Females have usually more convex abdomen. Spermatheca with duct heavily sclerotized in proximal part, soft in shorter basal part, with specific junction to bursa copulatrix (Figs 26–30). Nodulus poorly developed, gradually connected with cornu.
Host plants. Oulema duftschmidi and O. melanopus are well known European pests of cereals (O. melanopus introduced also to North America) and can be frequently found on various Poaceae. Host plants of O. rufocyanea (Suffrian, 1847), O. mauroi sp. nov., O. verae sp. nov. are not known, but we presume also some Poaceae species. ROZNER & ROZNER (2008) published Lamium spp. as host plant of O. rufocyanea in Macedonia but as other species of this group are associated with Poaceae, the occurrence on Lamium spp. should be verified. Eastern Palaearctic O. oryzae is associated with Oryza sativa.
Comments on identification. All European species are habitually extremely similar. As shown in Tab. 1, ratios of the main measurements widely overlap and cannot be used for species separation – with the exception of the elytral length / elytral width ratio which helps to separate three units: O. duftschmidi and O. melanopus, intermediate O. verae sp. nov. and finally, O. rufocyanea and O. mauroi sp. nov. The absolute measurements seem to be more useful, particularly body length, elytral length, elyral width and length of antennae, but also here the measurements partially overlap. The only really reliable characters to distinguish the species are the shape of the flagellum in males and the shape of the spermatheca in females, particularly the length and shape of the soft distal part of ductus spermathecae and its junction to bursa copulatrix. Surprisingly, the shape of spermatheca itself is almost invariable in this group and, on the contrary, the shape and number of coils of the well sclerotized proximal part of ductus spermathecae seem to be too variable and can only partially be used for identification.
description: Published as part of Bezděk, Jan & Baselga, Andrés, 2015, Revision of western Palaearctic species of the Oulema melanopus group, with description of two new species from Europe (Coleoptera: Chrysomelidae: Criocerinae), pp. 273-304 in Acta Entomologica Musei Nationalis Pragae 55 (1) on pages 279-280, DOI: 10.5281/zenodo.5303691