﻿Illustrated key to the European genera of Opiinae (Hymenoptera, Braconidae), with the description of two new Palaearctic genera and two new species

﻿Abstract An illustrated key to the European genera of the subfamily Opiinae (Hymenoptera, Braconidae) is presented and two new genera are described and illustrated: Cavopiusgen. nov. (type species: Opius (Agnopius) daghoides Zaykov & Fischer, 1983) from West and East Palaearctic regions and Pseudosteresgen. nov. (type species: Biosteresadanaensis Fischer & Beyarslan, 2005) from West Palaearctic region. Two new species are described and illustrated: Cephaloplitesgijswijtisp. nov. from Greece and Cavopiusdepressoriussp. nov. from S. Korea. Opius (Hypocynodus) kilisanus Fischer & Beyarslan, 2005 is a new synonym of Cephaloplitesmocsaryi Szépligeti, 1897. The following new combinations are proposed: Cavopiusdaghestanicus (Telenga, 1950), comb. nov., C.daghoides (Zaykov & Fischer, 1983), comb. nov., Pseudosteresadanaensis (Fischer & Beyarslan, 2005), comb. nov., P.arenaceus (Jakimavičius, 1986), comb. nov., P.christenseni (Papp, 1982), comb. nov., P.pseudarenaceus (Fischer & Beyarslan, 2005), comb. nov., and P.riphaeus (Tobias, 1986), comb. nov. Keys to species are provided for Cavopiusgen. nov., Cephaloplites Szépligeti, 1897, and Pseudosteresgen. nov.


Introduction
Opiinae is a large subfamily of the family Braconidae with ca 2,000 valid species and 39 genera according to Yu et al. (2016). It is a common group containing generally small (body length 2-5 mm) parasitoid wasps of mainly mining or fruit-infesting dipterous larvae. The subfamily has a worldwide distribution and its species have been reviewed by Fischer (1972Fischer ( , 1977Fischer ( , 1986Fischer ( , 1987. Wharton (e.g., 1987Wharton (e.g., , 1988Wharton (e.g., , 1997 published important updates and some additions for the existing keys to the genera of Opiinae, but the number of genera and the limits of some genera remain a matter of discussion, especially of Opius Wesmael, 1835 and of Eurytenes Foerster, 1863. The host of subgenera as used by Fischer (e.g., 1972) is mainly based on one character only and some specimens can be assigned to three subgenera with the key by Fischer (1972) because of intermediate conditions. In Li et al. (2013) most of the subgenera used by Fischer in his revisions were synonymised, but Phaedrotoma Foerster, 1863 was recognised as a valid genus for the species with symmetrical mandibles and excluded from the genus Opius Wesmael (following van Achterberg (1997Achterberg ( , 2004 and van Achterberg and Salvo (1997)). However, this proved problematic because of intermediate specimens, even belonging to the same species and, therefore, Phaedrotoma is here synonymised with Opius.
Among the large collection of Opiinae in Naturalis Biodiversity Center (Leiden) two new genera were discovered and a new species of the rare genus Cephaloplites Szépligeti. The new taxa are described, keyed, and illustrated below and an illustrated key to the genera is provided. This paper is part of the revision of the European species of the subfamily Opiinae.
In this paper the criterium for recognition as a separate (new) genus is the possession of a set of presumably derived characters. The results of molecular research published in Li et al. (2013) support, at least partly, the choices made as far as taxa were included but also show that the inclusion of Phaedrotoma in Opius makes the latter genus more polyphyletic. Unfortunately, Opius s.l. lacks a set of derived characters, but we do not yet have enough knowledge of the phylogeny of the Opiinae to solve this problem.

Materials and methods
The specimens were either collected in a Malaise trap or collected by using a sweep net. The Malaise trap specimens were chemically treated with a mixture of xylene + alcohol 96% and amylacetate, respectively (AXA-method; van Achterberg 2009). For identification of the subfamily Opiinae, see van Achterberg (1990Achterberg ( , 1993; for references to the Opiinae, see Yu et al. (2016).
Morphological terminology follows van Achterberg (1988van Achterberg ( , 1993, including the abbreviations for the wing venation. Measurements are taken as indicated by van Achterberg (1988): for the length and the width of a body part the maximum length and width is taken, unless otherwise indicated. The length of the mesosoma is measured from the anterior border of the mesoscutum to the apex of the propodeum and of the tergite I from the posterior border of the adductor to the medio-posterior margin of the tergite.
Observations and descriptions were made either under an Olympus SZX11 stereomicroscope. Photographic images were taken with a Canon 5Ds 50.6-megapixel camera combined with a Canon MP-E 65 mm f/2.8 1-5× Macro lens, Laowa Macro Twin flash KX-800 and an electronic WeMacro Z-stepper rail. The photos were stacked with Helicon Focus 7 software. The type specimens are deposited in the Naturalis collection (RMNH) at Leiden. NMW and ZISP stand for Naturhistorisches Museum at Vienna and Zoological Institute at St. Petersburg, respectively. Etymology. From cavus (Latin for hollow) and the generic name Opius Wesmael, because of the long and curved setae make a kind of cave at the back of the head (Fig. 13). Gender: masculine.
Description. Holotype, ♀, length of body 3.2 mm, of fore wing 3.4 mm. Head. Antenna with 37 segments and 1.2× as long as fore wing; third segment 1.2× longer than fourth segment, length of third, fourth and penultimate segments 1.5×, 1.2× and 1.4× their width, respectively (Figs 29, 33); width of head 2.1× its median length in dorsal view, smooth dorsally and posteriorly; behind stemmaticum with indistinct depression; vertex flattened and sparsely setose; OOL: diameter of ocellus: POL= 3:1:2 (Fig. 26); anterior half of frons shallowly depressed and smooth, its posterior half smooth and laterally setose (Fig. 26); face largely smooth, shiny and with conspicuous, long setae (Fig. 30); clypeus distinctly convex, semi-circular, largely smooth (except punctulation because of very long setae) and its ventral margin thin and straight, width of clypeus 2.8× its maximum height and 0.5× minimum width of face; hypoclypeal depression large and deep (Fig. 30); eye in dorsal view 1.4× longer than temple and temple behind eye subparallel-sided (Fig. 26); occipital carina distinct but dorsally and ventrally (behind malar space) absent (Fig. 31); temple and malar space smooth; length of malar space 1.1× basal width of mandible and 0.4× height of eye; malar suture deep and complete; mandible rather twisted apically but upper tooth robust, basally symmetrical or nearly so, basal half with ventral carina (Figs 30, 31); length of maxillary palp 1.1× height of head; labial palp segments robust.

Metasoma.
Tergite I 1.1× as long as wide apically and slightly widened apically, its surface convex medially and largely rugulose-punctate, dorsal carinae rather weakly developed and nearly up to apex of tergite (Fig. 27); tergite II and following tergites smooth; second suture absent dorsally; apex of tergites III-VI and antero-medially tergites IV-VI membranous and slightly sclerotised (more or less depressed in dead specimen; Figs 27, 28); setose part of ovipositor sheath 1.21× as long as fore wing, 8.1× tergite I and 3.6× as long as hind tibia; hypopygium acute ventro-apically and approximately as long as tergite I (Fig. 28).
Diagnosis. Hypoclypeal depression usually medium-sized, and medially ventral margin of clypeus above upper level of condyles of mandibles, but depression absent in P. riphaeus and narrow in P. adanaensis (Fig. 35); mandible with a large ventral tooth and its outer side convex (Fig. 40), mandible not twisted apically and second tooth clearly visible; notauli largely absent posteriorly (Fig. 36); medio-posterior depression of mesoscutum present; scutellum punctate medio-posteriorly; precoxal sulcus either absent, as a smooth and narrow suture or depressed and distinctly crenulate; precoxal sulcus without a second sculptured sulcus below; vein m-cu of fore wing slightly converging to vein 1-M posteriorly (Fig. 34) or parallel; vein r more or less angled with vein 3-SR of fore wing; vein 3-SR of fore wing 1.2-1.6× longer than vein 2-SR; vein m-cu of fore wing antefurcal or interstitial; pterostigma elliptical ( Fig. 34) or elongate triangular; hind tibia without oblique carina basally; dorsope present (Fig. 41); hypopygium of ♀ truncate.
Description. Holotype, ♂, length of body 1.7 mm, of fore wing 2.0 mm. Head. Antenna with 25 segments and as long as fore wing; third segment 1.3× longer than fourth segment, length of third, fourth and penultimate segments 3.0×, 2.1× and 1.7× their width, respectively, and apical segment with minute spine (Figs 54, 55); width of head 2× its median length in dorsal view, mainly smooth dorsally and posteriorly; behind stemmaticum without distinct depression; vertex convex and sparsely setose; OOL: diameter of ocellus: POL = 7:3:4 (Fig. 52); frons shallowly depressed medially and mainly smooth, medio-posteriorly with groove ( Fig. 52; eye in dorsal view 1.1× longer than temple and temple behind eye subparallel-sided (Fig. 52); face with pair of distinctly protruding convex and smooth tubercles (Figs 45, 53), visible in dorsal view of head (Fig. 52); long setose tentorial depression comparatively large and distinctly removed from base of mandible (Fig. 51); clypeus flat, triangular, smooth, shiny and its ventral margin thin and straight, width of clypeus 3.8× its maximum height and 0.8× minimum width of face; hypoclypeal depression medium-sized and deep (Fig. 51); occipital carina distinct but dorsally absent (Fig. 52); temple and malar space smooth; length of malar space 0.6× basal width of mandible and 0.2× height of eye; malar suture distinct, narrow and complete (Fig. 51); mandible weakly twisted apically, upper tooth slender, basally asymmetrical because of wide ventral lobe and no distinct ventral carina (Fig. 51); length of maxillary palp 0.7× height of head.
Metasoma. Tergite I 1.3× longer than its apical width and slightly widened apically, its surface convex medially and largely smooth (only some rugulae posteriorly), dorsal carinae weakly developed and nearly up to apex of tergite (Fig. 49); tergite II and following tergites smooth; second suture absent dorsally.
Colour. Black; temple, frons largely and face laterally reddish yellow; remainder of face, clypeus, malar space, antenna and tergite II dark brown; palpi brown; coxae and trochanters black or dark brown, remainder of legs brownish yellow; pterostigma and veins brown; wing membrane subhyaline (Fig. 46).

Cephaloplites mocsaryi Szépligeti, 1897 Figs 56-67
Cephaloplites mocsaryi Szépligeti, 1897: 600-601;Fischer 1972: 476-477;Papp 2004: 157 (type lost (Fischer 1964). Distribution. Czech Republic, Germany, Hungary, and Turkey (Asian part). Notes. The holotype of O. kilisanus has the mandible, malar space, temple ventrally, bases of hind and middle coxae and of trochantelli, mesosoma (except mesoscutum, scutellum, dorsal part of pronotum and mesopleuron) and metasoma (except second and most of tergite III) blackish, the temple somewhat less rounded and narrowed than figured for the female and the antenna with 26 segments. The differences are most likely clinal and considered to fall within the species limits of C. mocsaryi.  Notes. The venation of C. tadzhicus is similar to that of the type species (cf. Fig. 56), the protuberances of the face are small ( Fig. 70; not visible in dorsal view), the ♂ antenna with 28 segments, the metasoma dark brown as the remainder of the body, coxae, trochanters and trochantelli, the apex of the hind tibia and all tarsi infuscate to rather dark brown.