Aleiodes apiculatus (Fahringer, 1932)

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 : 40-43

Aleiodes apiculatus (Fahringer, 1932) Figs 48-49, 50-62

Rogas apicalis Reinhard, 1863: 266 (not Brullé 1832) (examined).

Rhogas apiculatus Fahringer, 1932: 284 (replacement name).

Aleiodes apiculatus ; Shenefelt 1975: 1165; Papp 1991: 101 (as synonym of Aleiodes pallidator ); Belokobylskij et al. 2003: 398.

Rogas (Aleiodes) negativus Tobias, 1961: 123; Belokobylskij 2000: 60 (as synonym of Aleiodes apiculatus (Fahringer, 1932); paratype in BMNH examined).

Aleiodes negativus ; Shenefelt 1975: 1165.

Type material.

Holotype of Aleiodes apiculatus , ♀ (ZMB), “Type”, "Coll. H. Rhd", "Germania, [surroundings of] Bautzen", "Holotypus Rogas apiculatus Reinh., 1863, ♀, Papp, 1983", " Aleiodes pallidator Thunb., ♀, det. Papp, J., 1984/ var. apiculatus (Fahr.)". Paratype of Aleiodes negativus , ♀ (BMNH) from Russia (Siberia: Tuvinskaya ASSR).

Additional material.

*England (V.C.s 9, 17, 20, 23, 24, 29, 31), *Poland. Specimens in NMS, BMNH, RMNH, AAC.

Molecular data.

MRS028 (England EF115455, CO1 + EF115440, 28S), MRS064 (England KU682218, CO1), MRS079 (England KU682222, CO1), MRS407 (England KU682239, CO1).

Biology.

This rather poorly-known species is a probably monophagous parasitoid of Euproctis similis (Fuessly) ( Erebidae : Lymantriinae ), from which we have seen 5 rearings (England, Poland; A.A. Allen, S.D. Beavan, M.R. Shaw, L. Sukovata) in addition to a reared paratype of Aleiodes negativus from the same host. Although evidently not obligatorily so (see below), it is probably largely univoltine, and the winter is passed inside the diapausing host larva. The host is arboreal, and when parasitised shows strong climbing behaviour just before being mummified, such that mummies are formed in exposed positions. It was readily reared from Euproctis similis in culture, but quantitative data are not available owing to high overwintering mortality. The notes that follow relate to a single, virgin, female. This female showed great interest in an egg mass of its host, antennating the dense covering of setae left by the female moth, and probing also with the ovipositor but probably without attempting to oviposit except into fully eclosed larvae as they exited from the felted covering. Neither legs nor antennae were used to manipulate such hosts, and the process was achieved with a single insertion of the ovipositor. In subsequent trials, second instar hosts were offered naked, and it was clear that there was an injection of a temporarily paralysing venom (detected by a clear jerk of the wings) before actual oviposition took place, although the ovipositor was usually not removed in the interim. As with the emerging first instars, the use of antennae or legs to hold the host was minimal so usually the ovipositor was all that was in contact with the host, pinning it against the substrate, and oviposition usually took about (often just over) 2 minutes, without a period of post-oviposition assessment or at most with only a minimal one. The long setae of third instar hosts were a good deal harder for the female to penetrate, but some ovipositions into this instar also occurred.

In culture Aleiodes apiculatus proved to be, like its host, partly plurivoltine. The host invariably overwinters as a partly grown larva in a densely spun hibernaculum, and the adult moths appear in the following vi/vii. In captivity, a small proportion of host larvae (available from about vii onwards) from the resulting eggs fed up rapidly and produced a second generation of the moth, while the majority developed only slowly and entered hibernation in the autumn (often not until the end of ix) while still relatively small, joined at that time by offspring of the second generation. The parasitoid invariably overwinters as a small larva within these diapausing hosts. From overwintering hosts mummification takes place in about ( v–)vi the following year, and emergence of the adult parasitoids in about ( vi–)vii, to oviposit into the young hosts that appear soon after. In host individuals with the accelerated growth pattern the host was mummified in about viii and the adult parasitoids emerged in ix (N = 4). At this time host larvae, from both generations, are still available prior to constructing their hibernacula. The cohort of hosts with accelerated growth that produced a second generation during the culture experiments arose in control groups as well as among the parasitised hosts, so this behaviour was not the result of having been parasitised: rather, it seems likely that only the growth of host individuals independently destined for a second generation would have provoked similar early development by the parasitoid. Hosts bearing the parasitoid entered winter diapause on average an estimated 8-10 days sooner than unparasitised ones. For the hibernaculum, the parasitised hosts constructed a weak outer web, moulted, and then made a much denser inner chamber isolated from the exuvium, while unparasitised controls usually moulted before commencing construction of a single chamber. Parasitised hosts (N = 10) broke diapause in spring over a period of 22 days, on average 8.0 days later than controls (N = 9) which emerged from their hibernacula over a period of 11 days (see also Aleiodes pallidator which exhibits similar behaviour).

Despite the possibility of plurivoltinism revealed in culture experiments the capture dates, in Britain ( vi–)vii–ix(– x), suggest that a single generation of rather long-lived individuals is the norm. It appears to have colonised Britain only recently; the first specimens known to us were collected in 1999 in Berkshire, since when it has been taken in MV traps in the SE corner of England fairly regularly. It is unlikely to have been long-overlooked in Britain, as its rather common and attractive host larva is conspicuous, readily identified, often reared and, when mummified by this parasitoid, often easily seen in a sun-exposed position.

Diagnosis.

Head transverse in dorsal view and directly narrowed ventrally in anterior view; eye rather large; OOL 0.5 × width of posterior ocellus; scapus and pedicellus of ♀ at least partly blackish, contrasting with yellowish middle of antenna and antenna of ♀ in dorsal view bicoloured, first–fifth[– eighth] and few apical segments more or less dark brown, remainder of antenna yellowish, antenna of ♂ entire yellowish; antennal segments of ♀ 46-49; length of malar space of ♀ 0.25-0.30 × height of eye in lateral view (Fig. 60; of ♂ 0.30 times); speculum of mesopleuron granulate and with satin sheen; fore wing rather narrow (Fig. 50); vein m-cu of fore wing straight and angled to vein 2-CU1 (Fig. 50); pterostigma dark brown with its basal half largely pale yellow; hind femur about 4.5 × as long as its maximum width; hind trochantellus about 2.6 × as long ventrally as wide (Fig. 53); hind tibia completely brownish yellow (Fig. 53); tarsal claws with distinct fine pecten (Fig. 54); dorsal face of propodeum medium-sized and rounded posteriorly (Figs 51, 52), first metasomal tergite lamelliform protruding latero-anteriorly (Fig. 62); second metasomal tergite rather stout and with minute smooth triangular area medio-basally (Fig. 52); third tergite finely sculptured; apical half of third and fourth tergite without sharp lateral crease and superficially granulate and with satin sheen; fourth metasomal tergite of ♀ black latero-posteriorly (Figs 52, 53; of ♂ brownish yellow).

Description.

Redescribed ♀ (NMS) from England, length of fore wing 5.9 mm, of body 6.8 mm.

Head. Antennal segments of ♀ 47, length of antenna 1.2 × fore wing, its subapical segments 1.6 × as long as wide; frons granulate, with satin sheen and some rugae; OOL and POL 0.5 and 0.6 × width of posterior ocellus, respectively; stemmaticum strongly protruding; vertex rugulose-granulate, with satin sheen; clypeus convex and punctulate-coriaceous; ventral margin of clypeus thick and convex (Fig. 59); width of hypoclypeal depression 0.4 × minimum width of face (Fig. 59) and face mainly granulate with transverse rugulae; length of eye 3.4 × temple in dorsal view and temple moderately narrowed behind eye; occiput behind stemmaticum rugulose-granulate; occipital carina reduced medio-dorsally and complete ventrally, without crenulae and dorsally curved (Fig. 61); clypeus above lower level of eyes (Fig. 59); length of malar space 0.30 × height of eye in lateral view; eyes rather protruding (Figs 59-61).

Mesosoma. Length of mesosoma 1.7 × its height; mesoscutal lobes finely granulate, matt, but medio-posteriorly irregularly rugose and anteriorly high; notauli medium-sized and crenulate; prepectal carina medium-sized, remaining separate far from anterior border; precoxal area of mesopleuron and area above it distinctly rugose; remainder of mesopleuron (including speculum) granulate and with satin sheen (Fig. 51); metapleuron distinctly granulate and with satin sheen; mesosternal sulcus shallow and sparsely crenulate; mesosternum rather angulate latero-posteriorly but rounded medially; scutellum slightly convex, finely granulate, and antero-laterally with carina; propodeum weakly convex, without tubercles, anteriorly granulate, medially coarsely rugose and posteriorly with longitudinal carinae, median carina complete.

Wings. Fore wing: r 0.3 × 3-SR (Fig. 50); 1-CU1 slightly oblique, 0.5 × as long as 2-CU1; r-m 0.6 × 2-SR, and 0.45 × 3-SR; second submarginal cell rather long (Fig. 50); cu-a slightly inclivous, not parallel with CU1b, straight (Fig. 50); 1-M straight posteriorly and 1-SR angled to 1-M. Hind wing: marginal cell parallel-sided, but slightly narrowed submedially; 2-SC+R medium-sized, slender; m-cu short and only slightly pigmented; M+CU:1-M = 4:3; 1r-m 0.7 × 1-M.

Legs. Tarsal claws rather small and with distinct fine pecten (Fig. 54); hind coxa finely granulate, with satin sheen and 0.8 × as long as first tergite; hind trochantellus 2.6 × longer ventrally than wide; length of fore and hind femora 6.0 and 4.6 × their width, respectively; inner apex of hind tibia without distinct comb; length of inner hind spur 0.35 × hind basitarsus.

Metasoma. First tergite 1.1 × as long as wide posteriorly, stout, convex anteriorly and latero-anteriorly distinctly lamelliform; first and second tergites densely coarsely longitudinally rugose (Fig. 52), third tergite basally rugulose and with distinct median carina up to middle of third tergite; medio-basal area of second tergite minute; second suture rather wide and crenulate; remainder of third tergite granulate and following tergites shiny and superficially granulate; apical half of third and fourth tergites without sharp lateral crease; ovipositor sheath densely setose and apically truncate.

Colour. Brownish yellow; scapus and pedicellus of ♀ at least partly blackish, contrasting with yellowish middle of antenna and antenna of ♀ in dorsal view bicoloured, first–fifth[– eighth] and 2-3 apical segments more or less dark brown, remainder of antenna yellowish; malar space, mandible, palpi, tegulae, pronotum anteriorly, basal half of pterostigma, trochanters and trochantelli, fore and middle coxae, and ventral half of metasoma ivory or pale yellow; face medially, frons and vertex medially, stemmaticum, occiput dorsally, mesoscutum laterally narrowly, scutellar sulcus, axilla, scutellum posteriorly, metanotum, third (except antero-lateral corner)-sixth tergites, fourth–sixth sternites and ovipositor sheath black or dark brown; telotarsi slightly infuscate; veins and apical half of pterostigma dark brown; wing membrane slightly infuscate.

Variation. Antennal segments of ♀ 46(1), 47(10), 48(4), 49(1); ♂ 41(1), 42(2), 43(8), 44(3), 45(6), 46(2). Length of fore wing 5-6 mm, of body 5-7 mm. Males are brownish yellow, but stemmaticum black and antenna apically, occiput dorsally, mesoscutum laterally, scutellum posteriorly, metanotum, propodeum medially, first tergite except posteriorly and second tergite laterally somewhat infuscate; malar space, palpi, tegulae, pronotum, fore and middle coxae, trochanters and trochantelli, first tergite medio-apically and middle of second tergite pale yellowish.

Notes.

Similar to Aleiodes pallidator (Thunberg), but the latter differs by having the tarsal claws only bristly setose, the hind trochantellus ventrally 2.2 × as long as wide, the antennal segments of ♀ with 51-57 segments; the stemmaticum less protuberant, the pterostigma yellow and the body of ♀ entirely brownish yellow. The extent of dark colouration is highly variable, and is often poorly developed in the British population. In males especially, the colour (including scape and even stemmaticum) can be rather uniform orange to light honey-brown. Because it can lack the colour characters usually plain in females, the male of this species can superficially resemble some of the relatively large orange species with big ocelli and antennal segments in the range 41-48 that fall into the residual circumscriptus -group not dealt with in this paper. Good recognition characters for male Aleiodes apiculatus include its somewhat bristly antenna and legs, its enlarged fifth tarsal segment (especially in the fore leg), its relatively strongly sculptured second metasomal tergite with weak mediolateral depressions, its weakly pectinate claws, and the stronger (though weak) development of a comb at the apex of the hind tibia. The synonymy with Aleiodes negativus (Tobias) is accepted; the examined females of Aleiodes apiculatus have the antenna with 46-49 segments (the holotype has 49 segments). The examined paratype of Aleiodes negativus (BMNH) was reared from Euproctis similis and has 47 antennal segments. According to Tobias (1961) Aleiodes negativus female types (including the holotype) should have 35-38 antennal segments and the male types 42-43 segments; most likely the antennal counts for the female types given by Tobias result from a lapsus or typographical error and should be 45-48.