The Species of Four Genera of Metopiinae (Hymenoptera: Ichneumonidae) in Britain, with New Host Records and Descriptions of Four New Species
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Journal of Natural History, 2005; 39(26): 2389–2407 The species of four genera of Metopiinae (Hymenoptera: Ichneumonidae) in Britain, with new host records and descriptions of four new species GAVIN R. BROAD1,2 & MARK R. SHAW3 1Centre for Ecology and Hydrology, Abbots Ripton, Huntingdon, UK, 2The Natural History Museum, London, UK, and 3National Museums of Scotland, Edinburgh, UK (Accepted 10 January 2005) Abstract Two genera of Metopiinae are recorded for the first time from the British Isles, Ischyrocnemis Holmgren and Synosis Townes. An account is also given of a further two genera, Apolophus Townes and Stethoncus Townes, that have been recently recorded from Britain but remain little known. Apolophus and Synosis are shown to be koinobiont endoparasitoids of Lepidoptera larvae of the families Schreckensteiniidae and Yponomeutidae, respectively. Four species are described as new: Stethoncus monopicida sp. nov., Synosis caesiellae sp. nov., Synosis fieldi sp. nov., and Synosis parenthesellae sp. nov. A key to the Western Palaearctic species of Synosis is provided. Keywords: Apolophus, British Isles, Ischyrocnemis, Metopiinae, Stethoncus, Synosis Introduction Although the British fauna is better known than that of almost any other country, the species composition of certain groups is still far from completely known. Detailed studies of collections of the parasitoid Hymenoptera repeatedly reveal numerous species new to the British fauna and species new to science. For example, Shaw and Hochberg (2001) calculate changes of between 20% and 49% in the British list following the monographing or otherwise detailed study of various ichneumonid and chalcidoid groups. Fitton et al. (1978), in the most recent checklist of British Hymenoptera, include species of nine genera of Metopiinae. Recent collecting and rearing efforts allow us to add two genera (Ischyrocnemis Holmgren and Synosis Townes) to the British list, representing four species, in addition to the two other genera (Apolophus Townes and Stethoncus Townes) that have been recorded by others (Owen et al. 1981 and Gauld and Sithole 2002, respectively) since Fitton et al. (1978). Here we describe four new species of Metopiinae (three species of Synosis and one of Stethoncus) and illustrate the species of Ischyrocnemis and Apolophus found in Britain. Host data for the genera Apolophus and Synosis are recorded for the first time. Vikberg (1972) noted that a specimen of Synosis clepsydra Correspondence: Gavin Broad, Centre for Ecology and Hydrology, Monks Wood, Abbots Ripton, Huntingdon PE28 2LS, UK. Email: [email protected] Published 30 June 2005. ISSN 0022-2933 print/ISSN 1464-5262 online # 2005 Taylor & Francis Group Ltd DOI: 10.1080/00222930500102074 2390 G. R. Broad & M. R. Shaw Townes from Canada was reared from a geometrid cocoon but no other details were provided and this must be treated as an uncertain host record. The Metopiinae comprises 27 genera (Yu and Horstmann 1997; Gauld and Sithole 2002), with a moderate numbers of species. Townes (1971) produced a key to genera which works well for all genera likely to be found in Britain. Fitton (1984) and Gauld and Sithole (2002) provide good introductions to the biology of Metopiinae. Briefly, all species for which the biology is known are koinobiont endoparasitoids, ovipositing into Lepidoptera larvae and emerging as adults from the host pupa. The distinctive appearance of metopiines, most having a strongly convex face, broad pronotum, fairly thick antennae and foreshortened tarsal segments, are presumed to be adaptations to pushing through semi-resistant substrates such as partially silken host retreats. Methods Many of the reared specimens of Apolophus and Synosis were obtained under the careful protocols described by Shaw (1997), and are accompanied by host remains. Because of the small number of specimens available, scanning electron microscopy was conducted only on uncoated specimens, using a Leo 1455VP low vacuum scanning electron microscope at The Natural History Museum, London. Wings or other body parts were not removed. Digital images were edited using Adobe PhotoshopH 6.0 and Adobe IllustratorH CS. Specimens reported here are deposited either in the National Museums of Scotland, Edinburgh (NMS), The Natural History Museum, London (BMNH), or the American Entomological Institute (AEI). Terminology Morphological terminology follows Gauld et al. (2002). Figure 1 illustrates the propodeal carinae as seen in the genus Synosis. Under the ‘‘Material examined’’ sections of the species descriptions, host species, and collection and emergence dates are prefaced ‘‘ex’’, ‘‘coll.’’, and ‘‘em.’’, respectively. Apolophus borealis Townes Diagnosis In the British fauna, Apolophus borealis is recognizable by the clypeus and face forming a continuous, moderately convex surface (Figure 2); thin mandibles with the lower tooth shorter than the upper (Figure 2); lower face elongate, with long malar space (Figures 2, 3); quadrate areolet; triangular, fairly long hypopygium, reaching to the end of the metasoma (Figure 4); and deep glymmae on the first tergite. The habitus of the genus is illustrated in Figure 5. Biology 1R and 2„ specimens of A. borealis were reared from pupae of Schreckensteinia festaliella (Hu¨bner) (Lepidoptera: Schreckensteiniidae) collected as larvae on Rubus. Species of Metopiinae in Britain 2391 Figure 1. Propodeum of Synosis parenthesellae „, with carinae and areas marked. Material examined England, UK: 1R, Leicester, September 1973 (J. Owen) (AEI); 2„„, Cornwall, Marsland Mouth, SS2117, ex Schreckensteinia festaliella (Hu¨bner), coll. 14 June 1998, em. July 1998 (J. L. Gregory) (NMS); 1R, Cornwall, Truro/Tregony, SW8844 ex S. festaliella on Rubus fruticosa agg., coll. 11 October 1998, em. 26 November 1998 (J. L. Gregory) (NMS). Comments Although Townes (1971) had tentatively included it in Metopiinae, Porter (1998) suggested that Apolophus may belong in the Mesochorinae, and indeed the shape of the hypopygium and areolet are very mesochorine-like, with the configuration of the posterior end of the metasoma closely resembling that of Varnado Wahl (illustrated by Wahl 1993). However, as pointed out by Gauld and Sithole (2002), the fore and mid tarsal segments of Apolophus are foreshortened (Figure 3), as in Metopiinae, and Gauld and Sithole (2002) suggest that Apolophus is a rather plesiomorphic member of the Metopiinae. We can now confirm that A. borealis is a primary larval–pupal parasitoid of Lepidoptera, as are other metopiines. In addition to the previous British record (Owen et al. 1981), A. borealis has now been recorded from Germany, Austria, Poland, Russia, Ukraine and the USA (Townes 1971; Yu and Horstmann 1997; Horstmann 2001), whilst further, mostly undescribed, species of Apolophus are known from South and Central America (Townes 1971; Porter 1998; Gauld and Sithole 2002). 2392 G. R. Broad & M. R. Shaw Figures 2–5. Apolophus borealis R. (2) Head, lateral view, showing narrow mandible. (3) Head and fore leg, showing long malar space and foreshortened tarsal segments. (4) Metasomal apex, showing large hypopygium. (5) Whole insect, lateral view. Ischyrocnemis goesi Holmgren Diagnosis Ischyrocnemis contains two described species, both from Europe. Nothing is known about their biology. The type species, I. goesi Holmgren, has been recorded from Austria, Denmark, Lithuania, Russia, Ukraine, Germany, Italy (Yu and Horstmann 1997; Jonaitis 2000; Horstmann 2001; Stoch 2003), China (Sheng and Zhang 1998), and now Britain. Ischyrocnemis goesi is readily separated from I. quadridens (Perkins) by the absence of glymmae on metasomal tergite 1, the long and strong fore tibial tooth (short and inconspicuous in I. quadridens) and the undivided mandibular teeth (mandibles appearing quadridentate in I. quadridens) (Perkins 1962). In the British fauna, I. goesi can be recognized by the clypeus and face forming a continuous, slightly convex surface; clypeus produced ventrally into a tooth (Figure 6); propodeum with areas superomedia and basalis combined into a long, narrow area demarcated by strong lateromedian longitudinal carinae; Species of Metopiinae in Britain 2393 Figures 6, 7. Ischyrocnemis goesi R. (2) Head, anterior view. (3) Whole insect, lateral view. all laterotergites broad and laterotergites 3 onwards not separated from their tergites; metasoma clavate, rounded apically with tergites 1–7 visible (Figure 7); ovipositor very short; fore tibia apically with a tooth; and areolet of fore wing roughly triangular and distinctly petiolate. Material examined England, UK: 2RR, Frilford Heath, Oxon., SU442986, Malaise trap, 18 June to 12 July 1991 (K. Porter) (NMS). Comments The correct taxonomic position of this genus is unclear. Townes (1971) placed Ischyrocnemis in Metopiinae but with the caveat that this was a very tentative assignment. The relatively slender first tergite of the metasoma and the rather flat, as opposed to distinctly convex, face are unusual features for Metopiinae. Perkins (1962) treated this genus as a member of the Ctenopelmatinae, close to Rhorus Fo¨rster (now placed in the Pionini). Until this genus (and other aberrant ‘Metopiinae’) can be included in a phylogenetic analysis that treats the varied elements of Ctenopelmatinae, we retain it provisionally in Metopiinae. Genus Stethoncus Townes Diagnosis Stethoncus is a small genus with only four previously described species. The genus has a wide distribution, being found in Southern India (S. indicator Aubert (Aubert 1965)), the Palaearctic (S.