Aleiodes diarsianae, van Achterberg, Cornelis & Shaw, Mark R., 2016

van Achterberg, Cornelis & Shaw, Mark R., 2016, Revision of the western Palaearctic species of Aleiodes Wesmael (Hymenoptera, Braconidae, Rogadinae). Part 1: Introduction, key to species groups, outlying distinctive species, and revisionary notes on some further species, ZooKeys 639, pp. 1-164 : 65-69

Aleiodes diarsianae sp. n. Figs 152-153, 154-164

Type material.

Holotype, ♀ (NMS), "[U.K.], Wales: Anglesey, Fedw Fawr, ex indet. Noctuid swept at night ex Calluna etc., 23.v.[19]97, mum. 29.v.[19]97, em. 16.vi.[19]97, died 1.ii.[19]98, M.R. Shaw, ♀ Aleiodes diarsianae in 1997 expts.", "Host remains compatible with Diarsia sp., possibly brunnea or mendica det M.R. Shaw, 2013". Paratypes (3 ♀ + 55 ♂): 42 ♂ (NMS, RMNH, BMNH) progeny of the holotype, 29 cultured in the noctuid Diarsia mendica (Fabricius), oviposition in range 26. vii– 3.viii.1997, mummification 18-27.v.1998, emergence 25. vi– 4.vii.1998 and 13 in Diarsia rubi (Vieweg), oviposition 23-30.viii.1997, mummification 4. iv– 9.v.1998, emergence 7-25.vi.1998; 1 ♂ (NMS) England: Westmorland, Arnside Knott, ex Diarsia? brunnea (Denis & Schiffermüller) on Calluna , coll. 5.v.1984, mum. 16.v.1984, em. 19.vi.1984, M.R. Shaw; 1 ♀ + 1♂ (NMS) Scotland: Orkney, ex Diarsia brunnea on Calluna , coll. v.1977, em. vi.1977, R.I. Lorimer; 1 ♀ (NMS) Scotland, East Perth, Drumderg, NO2055, ix.2012, A. Huff; 1 ♂ (NMS) Scotland, South Aberdeen, Glen Tanar 16. vii– 4.viii.1986, I. MacGowan; 1 ♂ (NMS) Scotland, South Aberdeen, Braemar, Morrone Birkwood, 12. vii– 6.viii.1984, B.D. Batty; 1 ♂ (NMS) Scotland, Easterness, Loch Garten, vi.1984, J.A. Owen; 3 ♂ (NMS) Scotland, Easterness, river Nethy shingle bank, NJ0214, 19. vi– 5.vii.1999 (1 ♂) and 5-19.vii.1999 (2 ♂), M. Edwards); 2 ♂ (NMS) Scotland, Elgin, Bognacruie, NJ0415 19. vii– 3.viii.1999 (1 ♂) and 3-23.viii.1999 (1 ♂), M. Edwards; 1 ♂ (NMS) Scotland, Elgin, Elchies, NJ2146, 27. vii– 9.viii.1999, B. Hicks; 2 ♂ (NMS) Scotland, Shetland, HU335730, 15-19.vii.2004, C. Sullivan; 1 ♀ (ZSSM), Netherlands: Nijmegen, ex Diarsia rubi , Bauer; 1 ♀ (RMNH), France: Besse en Chande SSE, Puy de Dôme, 13.vi.1976, H. Teunissen.

Molecular data.

MRS030 (Wales JF962600, CO1), MRS135 (Scotland KU682257, CO1 + EU854345, 28S).

Biology.

Univoltine and possibly partly plurivoltine parasitoid of low feeding noctuid larvae (especially, perhaps exclusively, Diarsia spp.) on moorland vegetation such as Calluna , overwintering in the host larva. Mummy (Fig. 153) probably made in concealment, blackish and swollen. The above list of paratypes includes specimens reared in culture, with the following experimental outcomes: Diarsia mendica (Fabricius) 1:47\45\\30+6; Diarsia rubi (Vieweg) 1:47\45\\33+5. In both cases mortality was rather heavy in the overwintering young larvae, as also in control groups. In Britain a northern insect, apparently restricted to broadly moorland habitats where it is a parasitoid of low-feeding noctuid larvae, possibly exclusively in the genus Diarsia . When using univoltine hosts it is certainly capable of being univoltine, overwintering as a small larva within the overwintering young host, which is killed in its penultimate instar to form a characteristic swollen mummy more or less concealed near ground level (in culture, all those from Diarsia rubi were made on tissues lining the base of the container; in the case of Diarsia mendica a small proportion formed on food plant, but again in low situations). At least one suitable host ( Diarsia rubi ) is at least partly plurivoltine; it is not entirely clear how the parasitoid responds to this, but Diarsia rubi larvae parasitised in culture in late viii all overwintered, while about 10% of the control cohort fed up to become autumn moths, which may suggest a tendency towards univoltine constraint by the parasitoid. The adults are long-lived and females can probably persist in the field from midsummer right through the latter half of the summer; on the other hand, some of the male collection dates recorded above are late enough to suggest plurivoltinism.

Diagnosis.

Apical half of hind femur (partly) dark brown, darker than hind trochanter and trochantellus (Fig. 157); face with distinct rugae; antenna of ♀ with 36-40 segments and third segment stout, of ♂ with 40-46 segments, 4 th– 7th antennal segments of both sexes stout (Fig. 164); OOL 1.4 × diameter of posterior ocellus (Fig. 163); clypeus 0.4 × as wide as face; mesosternum usually at least narrowly black posteriorly (Fig. 155); malar space and temple near eye dark reddish brown or dark brown; first tergite strongly widened apically (Fig. 156); eye elongate (of ♂) in lateral view; middle third of hind femur yellowish brown or dark brown; vertex moderately setose, rather shiny and more or less blackish or infuscate posteriorly; mesosternum variable, but dark brown in all British specimens; POL 1.2-1.7 × diameter of posterior ocellus; eye 2.2-2.5 × as long as temple in dorsal view (Fig. 163). Very similar to Aleiodes bistrigatus (Roman), but the latter has the temples less directly narrowed behind the eyes, 4 th– 7th antennal segments less robust and fewer antennal segments in the males. Similar to the Aleiodes pictus -aggregate (i.e. Aleiodes pictus ( Herrich-Schäffer, 1838) and Aleiodes nigriceps Wesmael, 1838) but these usually are smaller and less robust species, having the face without distinct rugae or only a few rugae dorsally, the mesosternum usually widely orange brown (and the mesopleuron usually without rugae in Aleiodes nigriceps ), the malar space partly or completely and the temple near the eye (= external orbita) yellowish brown, the first tergite less widened apically, the fore and hind tarsi comparatively slender, the mummy slender and usually brownish (Figs 231, 273), the eye normal in lateral view and the antenna less robust. The holotype is much darker than at the start of its life (it lived in a humid tube for over 7 months); this happens to most experimental females.

Description.

Holotype, ♀, length of fore wing 4.0 mm, of body 5.5 mm.

Head. Antennal segments of ♀ 40, length of antenna 1.3 × fore wing, its subapical segments about 1.5 × as long as wide and third segment stout (Figs 159-160, 164); frons coriaceous and posteriorly rugulose, with satin sheen; OOL 1.4 × diameter of posterior ocellus and coriaceous; vertex coriaceous, matt; clypeus slightly convex, indistinctly sculptured; ventral margin of clypeus rounded and depressed; width of hypoclypeal depression 0.36 × minimum width of face and face distinctly transversely rugose (Fig. 161); length of eye 2.5 × temple in dorsal view and temple rather directly narrowed behind eye (Fig. 163); occiput behind stemmaticum coriaceous and with some rugulae, occipital carina interrupted dorsally by somewhat less than width of ocellus (Fig. 163); clypeus partly above lower level of eyes and 0.4 × as wide as face (Fig. 161); length of malar space 0.5 × length of eye in lateral view; eyes moderately protruding (Figs 161-163).

Mesosoma. Mesoscutal lobes coriaceous, matt, but medio-posteriorly longitudinally rugose; notauli complete and moderately wide, weakly crenulate and posteriorly widened and rugose; prepectal carina medium-sized and lamelliform, reaching anterior border; precoxal area of mesopleuron largely widely rugose, mesopleuron above precoxal area (except nearly smooth and shiny speculum) largely rugose (Fig. 155); metapleuron coriaceous, matt and posteriorly rather tuberculate; mesosternal sulcus narrow and deep, absent and replaced by carina medio-posteriorly; mesosternum rounded posteriorly; scutellum elongate, slightly convex, coriaceous and laterally largely carinate; propodeum rather flat dorsally (depressed laterally and posteriorly, rather tuberculate latero-posteriorly) and strongly rugose but anteriorly weakly so, median carina complete, but posteriorly irregular.

Wings. Fore wing: r 0.3 × 3-SR (Fig. 154); 1-CU1 horizontal, 0.4 × as long as 2-CU1; r-m 0.65 × 2-SR, and 0.55 × 3-SR; second submarginal cell comparatively large (Figs 152, 154); cu-a weakly oblique, not parallel with CU1b, straight; 1-M slightly curved posteriorly. Hind wing: apical half of marginal cell parallel-sided or nearly so; 2-SC+R short and longitudinal; m-cu present and weakly pigmented (Fig. 154).

Legs. Tarsal claws setose; hind coxa coriaceous but partly superficially rugulose, largely matt; hind trochantellus 2.3 × longer than wide; length of fore and hind femora 5.1 and 4.3 × their width, respectively (Figs 157-158); inner apex of hind tibia without comb; length of inner hind spur 0.35 × hind basitarsus.

Metasoma. First tergite 0.8 × as long as wide posteriorly and latero-posteriorly narrowly lamelliform, moderately convex and flattened posteriorly, dorsope comparatively wide (Fig. 156); first–third tergites densely and distinctly longitudinally rugose, robust (Fig. 156), with distinct median carina; medio-basal area of second tergite absent; second suture moderately impressed and crenulate; remainder of metasoma largely superficially coriaceous; fourth and apical fifth of third tergite without sharp lateral crease; ovipositor sheath (except dorsally) densely setose.

Colour. Black or brownish black; antenna pale brown, but scapus dorsally and apical seventh of antenna dark brown; palpi, and tegulae pale yellowish (Fig. 152); orbita posteriorly and dorsally brownish yellow (Figs 162-163); mesosoma orange brown, but propleuron, mesoscutal lobes medially, metanotum laterally, anterior half of propodeum and metapleuron, mesopleuron dorso-posteriorly and mesosternum black; metasoma largely dark orange brown (Figs 152, 156); hind femur (except basally) fuzzy dark brown (Fig. 157) and remainder of legs yellowish brown; veins and pterostigma (except yellow basal 0.2 and apex) dark brown; border between dark and pale part of pterostigma sharp, contrasting with each other (Fig. 154); wing membrane subhyaline. This specimen had lived in a humid tube for 7 months, and its colour had deepened considerably over this time.

Variation. Length of fore wing 4.5-5.0 mm; antennal segments of ♀ 36(1), 38(3), 39(1), 40(1), of ♂ 40(2), 41(2), 42(4), 43(13), 44(16), 45(14), 46(3); mesosoma largely black to largely orange-brown; OOL of male slightly longer than diameter of posterior ocellus and apical half of antenna dark brown; fifth maxillary palp segment slender to moderately widened and rather long; first tergite (except medio-posteriorly) black (♂) or entirely dark reddish-brown (♀) and second tergite black or reddish laterally; in British females only posterior segments somewhat darkened; in British males first tergite more or less blackish in anterior half as well, but second and third tergites usually (almost) fully orange, sometimes with infuscation sublaterally on second tergite (especially anteriorly).; mesopleuron medially and propodeum rugose or superficially rugulose; few females seen, but in one very extensively orange specimen the legs are almost completely orange, with only slight infuscation in the apical half of hind femur. May be confused with Aleiodes borealis (Thomson, 1892), but this species has less antennal segments (♀: 32-34 segments), palpi and legs more or less infuscate and the clypeus wider (about 0.5 × width of the face).

We have seen 3 ♀ + 11 ♂ (NMS) from Sweden ( Bohuslän and Västerbotten) and Finland (Kuusamo and Saarijärvi) that come close to Aleiodes diarsianae , but differ in being less robust (T1 less expanded apically; antennal segments longer in relation to width, especially basally), less strongly sculptured (fewer rugae on face; mesopleuron with only weak rugae), and having somewhat larger eyes. They also have slightly more antennal segments, at least in the female sex (the two females with intact antennae have 44 and 45 segments, the males have 42(1), 43(1), 44(1), 45(6), 47(1)), and the females have T1 more or less extensively blackish in anterior half, unlike the British Aleiodes diarsianae females seen, in which it is uniformly orange. CO1 sequences have been obtained for two localities ( Västerbotten and Kuusamo; respectively MRS304 GenBank KU682234, and MRS692 GenBank KU682247): they form a well-isolated clade with Aleiodes diarsianae but differ from it by 8 fixed base-pairs. One of the Finnish males was reared from a noctuid mummy collected on a twig in a bog (N.R. Fritzén) later kindly identified from its CO1 sequence as Coenophila subrosea (Stephens) by Dr Katja Kramp (SDEI). Another male (in NMS) from Norway ( Turtagrö, Sogn og Fjordane) has 42 antennal segments and probably belongs to the same species; it was reared from an unidentified dark noctuid mummy on Betula nana (K.P. Bland), which, like the Finnish one, is somewhat swollen but not as extensively so as in the considerable number of British Aleiodes diarsianae mummies we have seen. Both of these specimens, in common with some (but not all) males from Sweden, have the maxillary palp more swollen than seen in the British material. More material is needed to settle the status of these Fennoscandian populations, but we provisionally regard them as probably a different species near Aleiodes diarsianae .

Etymology.

Named after the generic name of its host: Diarsia Hübner.

Distribution.

*British Isles (England, Wales, Scotland), *France, *Netherlands.

Note.

Males have on average about 3-4 more antennal segments than females.