Hyposoter rivulator Galsworthy & Shaw, 2023

Galsworthy, Anthony, Shaw, Mark R. & Haraldseide, Håkon, 2023, A key to European species of Hyposoter Förster, 1869 (Ichneumonidae: Campopleginae) with descriptions of 18 new species, and notes on all included species, Zootaxa 5290 (1), pp. 1-73 : 62-64

Hyposoter rivulator Galsworthy & Shaw sp. nov.

( Figs. 35, 36 )

Diagnosis. One of four species with black metasoma, pale fore and mid coxae, and more or less orange hind tibia, rivulator can be distinguished from monensis sp. nov. and pechipogator sp. nov. by its evenly granulate area petiolaris, and from dumeticola by its entirely yellow second sternite and its area basalis reduced to a single longitudinal keel. See also note under Hyposoter inquinatus .

Description. Female: fore wing length: 4–5 mm.

Head: face granulate, with even punctures spaced at about one diameter of puncture, and hard to discern against background sculpture, slightly longer than wide; clypeus a continuous surface with face, similarly sculptured and punctured, evenly convex, with a narrow shiny out-turned apex; mandibles evenly tapering, yellow with brown teeth; frons, vertex and temples similarly sculptured, temples narrowing strongly behind eyes; antenna with first flagellomere 3–4 longer than wide, flagellum with 29–32 flagellomeres.

Mesosoma: mesoscutum dull and granulate, with scattered punctures scarcely visible; notauli absent; mesopleuron strongly granulate in ventral half, with more closely spaced punctures; dorsal half and speculum more shiny, but all with a striate to cellular sculpture, nowhere smooth; metapleuron strongly granulate with closer punctures; propodeum evenly and much more finely granulate throughout; carinae greatly reduced, basal area represented by a narrow triangle, and front of area superomedia and costulae indicated by shallow carinae; rear of area superomedia without lateral keels, its distal corners indicated only by very slight raised bumps; legs rather slender, first segment of hind tarsus approximately equal to other segments together, claws strongly pectinate.

Wings rather narrow, 1 cu-a opposite basal vein; areolet small, narrowly quadrilateral, long-stalked; nervellus slightly curved, vertical.

Metasoma: petiole of first segment of metasoma parallel-sided, without dorsal or dorsolateral carinae, shiny, its basal half devoid of punctures, apical half with scattered punctures; postpetiole strongly expanded, with rather shiny cellular microsculpture; glymma large but rather shallow; all tergites dull with increasingly fine microsculpture, and minute scattered punctures; tergite 2 with small semicircular thyridiae close to basal edge; tergites 6–7 with straight apical edges; ovipositor slightly curved upwards, a little shorter than depth of metasoma, strongly notched dorsally.

Colour: black; antenna dark brown, becoming reddish brown towards apex; fore legs entirely and mid coxae, trochanter and trochantellus yellow, mid coxa slightly darkened in some specimens; hind coxa black, sometimes with some reddish suffusion; rest of mid and hind legs orange, hind tibia usually slightly darkened at base and apex; first sternite yellow, other sternites with dark transverse bands.

Male: very similar to female in coloration and sculpture, but petiolar area of propodeum with stronger keels, very broad and almost triangular. Flagellomeres 30–32.

Holotype: ♀, [ UK] Gait Barrows NNR, Lancs , ex Rivula sericealis , coll. 16.5.08, coc 30.5.08, em. 17.6.08, M.R.Shaw ( NMS). Paratypes: 2♀, same loc. and coll. date, coc 23.5.08 and 30.5.08, em 12.6.08 and 18. 6.08 respectively, M.R.Shaw ; 1♁, Flanders Moss, Stirlings ., Rivula sericealis , coll. 14.5.08, coc. 30.5.08, em 12.6.08, M.R.Shaw ; 1♀, 1♁, Monks Wood NNR, TL7919, ex Rivula sericealis on Brachypodium sylvaticum , 26.5.2009, coc 1.6.09, em 25.6.09 and 14.6.09 respectively, M.R.Shaw ; 3♀, Taynish NNR, Argyll , NR730845, Malaise trap, clearing in oak/alder wood; I.C. Christie, 9.vii–5.viii.1984, and 6–31.viii.1984, RSM 1984 -048; 1♀, Inverlussa, Jura , NR644872, Malaise Trap, 25–27.vii.1988, R.P. Knill-Jones, NMSZ1990 -063; 1♀, Croft Dhu, Tomatin, Inv. , NH818299, Malaise Trap, Garden nr. rough pasture, 5– 12.vi.1982, D. Horsfield, RSMNH1882.026 ; 4♁, Caldarvan , Dumbs . NS450836 Mal. trap, Mixed wood by pond, 7–18.vii.83 I.C.Christie ; 1♀, Chippenham Fen, Cambs ., TL650693, Malaise trap, carr at reedbed edge, 30.vii–11.viii.85, J. Field, RMSNH 1966-021 ; 2♀, Isle of Man, the Curraghs, Goshen , SC399950, 23–30.vii.1995, S.M.Crellin, Malaise Trap, NMSZ2003.044 (all in NMS); 1♀, Morden Hall Park, Surrey , TQ2668, Malaise Trap, 30.vi–6.vii.2017, A.C.Galsworthy, in NHMUK ; 1♀, Norway, Eis 21,: Aremark , Lindtjern , July 2012, Thor J Olsen, Hyposoter near, leucomerus det. Riedel 2014; 1♀, Georgien [Georgia], Lagodekhi NP, H1/6, Hyposoter ? det Riedel 2017 (both in coll. Matthias Riedel); 1♀, Belgique, Somal ; fauch sur une haie libre, jardin; 5.ix.2015; P.N. Libert rec. (Private collection P.N.Libert)

Biology: 5 specimens were reared from caterpillars of the Straw Dot moth, Rivula sericealis (Scopoli) ( Lepidoptera , Erebidae ) in three separate localities by M.R.Shaw (see Shaw, 2012).

Range: most of the specimens seen by us are from the UK; however, two of the paratypes listed below, kindly loaned to us by Dr M.Riedel, are from respectively Norway and Georgia. The latter in particular suggests that the species is widespread: the host species has a wide range stretching right across the Palaearctic from western Europe to Japan.

Figures

FIGURES 35–38. 35–36: Hypsoter rivulator sp. n. Habitus: 35 lateral, 36 dorsal. 37–38: Hyposoter ruficoxator sp. n. Habitus: 37 lateral, 38 dorsal.