Microchelonus miscellae sp. n.

Female (holotype). Body length 2.2mm. Head in front view oval, 1.2 times as wide as high, in dorsal view (fig. 1) roundly narrowed behind eye, 1.9 times as wide as long and 1.2 times as wide as mesonotum. Transverse diameter of eye 0.8 times the length of temple in dorsal view (fig. 1), eye 0.7 times temple in lateral view. Ocellar triangle as wide as OOL. POL twice as long as ocellar diameter. Longitudinal diameter of eye 1.7 times the transverse diameter, 0.8 times width of face, 2.5 times length of malar space. Face twice as wide as high, 1.4 times as high as clypeus. Maxillary palpus short, as long as height of face. Antenna with 16 segments, 3rd segment twice, 5th 1.5 times and 7th 1.3 times as long as wide, 13-15th wider than long, apical segment oval, longer than wide.

Mesosoma 1.4 times as long as high. Propodeum with a faint transverse carina, a pair of small lateral tubercles and a pair of small median tubercles. Forewing with pterostigma 1.5 times as long as metacarpus (fig. 2); 3rd abscissa of radial vein 5 times as long as 2nd, 1.5 times as long as 1st radiomedial vein; 1st abscissa of radial vein somewhat longer than 2nd abscissa (fig. 2). Hind femur 3.5 times as long as wide (fig. 3). Hind tibia as wide as hind femur, 4.5 times as long as its apical width (fig. 3), and 1.1 times as long as hind tarsus. Inner spur of hind tibia half as long as hind basitarsus. Apical segment of hind tarsus as long as 3rd, shorter than 2nd segment.

Carapace of metasoma oval, incurved apic.oventrally for 0.1 of its length, 1.7 times as long as wide (fig. 4), 3 times as long as high.

Head behind eye and face faintly transversely striate, frons and upper part of face concentrically striate, face otherwise longitudinally striate. Mesoscutum rugulose-punctate, without longitudinal rugae before the scutellum. Carapace reticulate-rugulose, without longitudinal rugae, apically with granulate sculpture.

Body black, fore and middle tibiae brown, hind tibia dark brown with a yellowish spot before the middle on inner face. Wings infuscate; pterostigma, metacarpus and costal vein brown, other veins light brown

Male. Body length 2.1-2.3mm. Head 1.3 times as wide as high in front view, roundly narrowed behind eye in dorsal view and twice as wide as long, 1.2 times as wide as mesoscutum. Transverse diameter of eye 0.7 times the length of temple in dorsal view, eye as long as temple in lateral view. Ocellar triangle somewhat wider than OOL (11 : 10). POL twice as long as ocellar diameter. Longitudinal diameter of eye 1.7 times the transverse diameter, 2.6-3.0 times length of malar space. Face twice as wide as high, 1.2 times as wide as longitudinal diameter of eye, 1.4 times as high as clypeus. Maxillary palpi as long as height of face and clypeus. Antenna with 18 segments (one specimen, the other without preapical segments); 3rd segment 2.2 times, 9th segment 1.5 times, 16th and 17th segments 1.1-1.2 times as long as wide, apical segment pointed oval, 1.6 times as long as wide.

Mesosoma 1.3 times as long as high. Propodeum with a faint transverse carina, a pair of widely rounded lateral tubercles and a pair of weak median tubercles. Pterostigma 1.35 times as long as metacarpus. 3rd abscissa of radial vein 5 times as long as 2nd abscissa and 1.7 times as long as 1st radiomedial vein; 1st abscissa of radial vein 1.5 times as long as 2nd. Hind femur 3 times as long as wide, wider than hind tibia (11 :9). Hind tibia 4.5 times as long as its apical width, 1.1 times as long as hind tarsus. Inner spur of hind tibia half as long as hind basitarsus. Apical segment of hind tarsus as long as 3rd.

Carapace of metasoma oval, 1.75 times as long as wide, incurved apicoventrally in 0.2 of its length. Apical aperture (- foramen) oval, almost 0.3 times as high as carapace, 0.3 times as wide as carapace; middle tubercle of apical aperture depressed laterally (figs 5,6).

Head with concentric wrinkles frontally, longitudinally striate along eye margin; vertex behind ocelli faintly transversely striate. Mesoscutum rugulose-punctate, areolate-rugose before scutellum and along notauli. Basal half of carapace areolate-rugulose, almost without longitudinal rugae, apical half faintly reticulate-rugulose.

Body black; fore and middle tibiae brown, basal third of hind tibia with a brownish spot. Wings infuscate, pterostigma and veins brown.

Holotype: ♀, “[ENGLAND] Buttlers Hangings NR, W. Wycombe, Bucks., ex Mompha miscella, Helianthemum, [coll.] 5.5.[19]79, em. 7.7.[19]79, M.R.Shaw”. (In National Museums of Scotland (NMS), Edinburgh). Paratypes. 1♂, England, Leckford, Hants., em. 21.v. 1982, ex Mompha miscella coll. 16.iv.1982 as larva, Helianthemum, EC. Pelham-Clinton; 1♂, England, Avon Gorge, VC 34, Bristol, ST 5673, em.2.viii.2000, ex miner in Helianthemum, probably Mompha miscella, D. Gibbs (both in NMS).

Microchelonus miscellae sp. n. is close to M. subcontractus (Abdinbekova, 1971) from south-east Europe, Caucasus, Kazakhstan, central Asia and the south of the Russian Far East (Tobias, 1997a), but it differs in having the hind tibia widened, the inner spur of the hind tibia longer (in M. subcontractus 0.4 as long as hind basitarsus), the carapace sculpture of the female without medial longitudinal rugae, the hind basitarsus dark coloured (in M. subcontractus usually yellowish). In having the hind tibia widened, M. miscellae sp. n. is similar to M. kirvus Tobias, 1997 from the Novgorod region of Russia (Tobias, 1997b) but differs in having the radial cell shorter (in M. kirvus the metacarpus is as long as the pterostigma), the sculpture of the female carapace without longitudinal rugae, and the sculpture of the mesonotum weaker.

Although evidently widely distributed at least in southern Britain, Microchelonus miscellae sp. n. may be only a minor component of the parasitoid complex of Mompha miscella, to judge from its absence from several moderately large collections of this host (MRS, unpublished data). Mompha (Lophoptilus) miscella occupies a rather isolated ecological as well as taxonomic position in the British Mompha fauna, being the only species to feed on Helianthemum (Cistaceae) while the remaining 13 British species (placed in the subgenera Anybia, Psacaphora and Mompha) all feed on species of Onagraceae (Koster, 2002). No examples of Microchelonus miscellae sp.nr have been reared from any of these, despite fairly extensive sampling of several of them (MRS, unpublished data). Cheloninae are solitary egg-larval koinobiont endoparasitoids - that is, the female parasitoid oviposits into the host egg and the host is not finally destroyed until its larval (or prepupal) stage - and oviposition into host eggs, which are poorly defended physiologically, may give chelonines a potential for a relatively wide host range (cf. Shaw & Huddleston, 1991). For this reason the host’s egg form and placement may be a more crucial determinant of host range than the systematic position or feeding biology of the host larva, and it is conceivable that some other species of small microlepidoptera - perhaps living, as Mompha miscella does, in base-rich grassland - will turn out to be a moré regular host(s) of this parasitoid.