Gasteruption boreale (Thomson, 1883)

Johansson, Niklas & van Achterberg, Cornelis, 2016, Revision of the Palaearctic Gasteruptionassectator aggregate, with special reference to Sweden (Hymenoptera, Gasteruptiidae), ZooKeys 615, pp. 73-94 : 75-82

Taxon classification Animalia Hymenoptera Gasteruptiidae

Gasteruption boreale (Thomson, 1883) stat. rev. Figs 8-11, 12-13, 14-15, 16, 17-18, 27, 29

Foenus borealis Thomson, 1883: 849; Hedicke 1939: 7; Hedqvist 1973: 181, 182 (invalid lectotype designation); Wall 1994: 148. Synonymized with Gasteruption assectator (Linnaeus) by Schletterer (1889) and with Gasteruption minutum (Tournier) by van Achterberg and Talebi (2014).

Gasteruption boreale ; Schletterer 1885: 303.

Foenus fumipennis Thomson, 1883: 848; Hedicke 1939: 7; Hedqvist 1973: 181, 182 (lectotype designation); Wall 1994: 148. Synonymized with Gasteruption assectator (Linnaeus) by Schletterer 1885. Syn. n.

Trichofoenus breviterebrae Watanabe, 1934: 285; Hedicke 1939: 45. Synonymized with Gasteruption assectator (Linnaeus) by Pagliano and Scaramozzino (2000). Syn. n.

Gasteruption margotae Madl, 1987c: 225-227, 1990b: 480; Wall 1994: 149. Synonymized with Gasteruption assectator (Linnaeus) by Madl (1990b). Syn. n.

Type material.

In Thomsons collection in MZLU four males and one female are placed at the label Foenus borealis . Hedqvist (1973) states that the type series by Thomson only consisted of three males and one female but this is probably a simple miscalculation. The female (from Norway) was originally selected as lectotype by Hedqvist (1973) but the selection was declared as invalid (van Achterberg and Talebi 2014) because the listed original locality of the type series (= Lappland) excludes the selection of a lectotype from Norway. One male (Figs 8-11) was designated lectotype by van Achterberg and Talebi (2014) and the species was synonymized with Gasteruption minutum (Tournier, 1877). All males and the female in the type series belong to one distinct species (see key below). The wider malar space exhibited by the lectotype is clearly shorter than the mandibular base and fits within the range of this species and is not as long as in Gasteruption minutum .

The type series of Gasteruption fumipenne consists of the lectotype from Gotland. The size, habitus, antennae and smooth sculpture on the mesoscutum of the lectotype (Figs 12-13) indicates, despite the lacking metasoma, that it concerns a female of Gasteruption boreale . This is the only specimen known from the Baltic island Gotland, but the type locality ("Olle hau"= Ulla hau, Fårö, Gotland, Sweden) was at the time of the collection an active sand dune field with old pines. It was quite a different ecosystem than at the mainland of Gotland where Gasteruption assectator is the most common (and now only?) of the three species. The other specimen under this label is a male of Gasteruption assectator from Scania ( Skåne). The synonymisation with Gasteruption assectator made by Schletterer (1889) is rejected and Foenus fumipennis is to be regarded as a new synonym of Gasteruption boreale (Thomson).

The type series of Gasteruption margotae consists of the male holotype (Figs 14-15) from Finland ( Madl 1987c); the holotype is a typical male of Gasteruption boreale (Thomson). The study of the holotype shows that the synonymisation with Gasteruption assectator made by Madl (1990) is unjustified after resolving the Gasteruption assectator aggregate and that Gasteruption margotae is clearly a new synonym of Gasteruption boreale (Thomson).

The examined type series of Gasteruption breviterebrae (Fig. 16) consists of the holotype female and a paratype male from Sakhalin (Far East Russia). The holotype shows the typical features of Gasteruption boreale (Thomson), viz., the less sculptured mesoscutum and the bristly ovipositor sheath. The slightly aberrant red marks on the metasoma fall within the geographical variation of Gasteruption boreale . The synonymisation with Gasteruption assectator made by Pagliano and Scaramozzino (2000) is here rejected and Trichofoenus breviterebrae is a new synonym of Gasteruption boreale (Thomson).

Additional material.

Sweden ( Småland: Bäckebo, Skillingaryd, Ränneslätt, Jönköping; Västergötland: Baskarp; Södermanland: Huddinge; Uppland: Rossholm; Dalarna: Leksand, Ludvika; Hälsingland: Hornslandet; Västerbotten: Vindeln, Hällnäs; Lycksele lappmark : Gällivare); Finland ( Åland: Hammarland; Åbo: Harvaluoto).

Diagnosis.

Head in dorsal view almost parallel-sided behind eyes, elongate, about as wide as long (Figs 9, 18). Occipital carina indistinct and not reflexed. Frons with satin sheen. Mesoscutum smooth, weakly rugose/shagreened with satin sheen, medio-posteriorly in front of scutellum rugose-reticulate (Figs 17-18, 27). Mesosoma and head silvery pilose. Mesosoma with a satin sheen, quite distinct from the rather matt gloss occurring in Gasteruption assectator . Whitish pubescence of eye of female mostly distinctly longer and denser than of Gasteruption assectator . Antenna slightly shorter than in Gasteruption assectator with sixth segment about 1.5 times longer than wide and subapical segment about 1.2 times longer than wide. Only apical half of hind coxa weakly striate dorsally. Hind tibia and basitarsus with white ring which might be interrupted ventrally. Metasoma mainly black with orange lateral patches on tergites 2-4 which might be partially reduced, especially in northern specimens. Inner sides of tibiae often red brown to orange with white or yellow basal patch indistinct on fore and middle tibiae. Ovipositor sheath black or brown, 0.7-1.0 times as long as hind tibia, its apical half entirely with stout, rather scarce black bristles angled backwards at about 45° (Fig. 29). The species is closely related to Gasteruption assectator (Linnaeus) but the female can be distinguished by the shorter ovipositor sheath, the less sculptured mesoscutum and the more scarce promi nent bristles on the apical half of the ovipositor sheath. The male is hard to distinguish from Gasteruption assectator and identification is not always possible with certainty. In most cases the male of Gasteruption boreale can however be separated from Gasteruption assectator by its slightly more elongated, parallel-sided head in dorsal view, the more or less enlarged malar space and its less sculptured mesoscutum.

Description.

Female. Length of body 6-11 mm (fore wing 3.5-5.5 mm)

Head. Temples parallel-sided behind eyes in dorsal view. Occipital carina not raised. Frons and vertex with satin sheen. Malar space short, at most about 0.5 times mandibular base. Hypostomal bridge narrow, at most 0.5 times mandibular base. Eyes with dense white pubescence. Antenna short; sixth segment about 1.5 times longer than wide and subapical segment about 1.2 times longer than wide.

Mesosoma. Surface largely smooth with satin sheen, mesoscutal sculpture of almost equal intensity as on vertex. Antesternal carina narrow, non-lamelliform. Pronotal sides with very small pointed teeth antero-ventrally, but these are sometimes entirely absent. Upper half of mesopleuron mostly considerably weaker sculptured than its more rugose lower part.

Legs. Hind tibia stout as in Gasteruption assectator . Hind coxa often with weaker rugae apically than on basal half, dissolving amidst rugose background. Hind tibial spurs often brighter than hind tibia.

Metasoma. Ovipositor sheath entirely black or brown, 0.7-1.0 times as long as hind tibia, its apical half entirely with stout, black bristles angled backwards at about 45° (Fig. 29).

Colour. Black. Mandible apically, hind tibial spurs and patches laterally on tergites 2-4 reddish brown. Patches rarely intercepted. Fore and middle tibiae mostly with indistinct yellow or ivory basal patch. Inner side of tibiae often orange. Basal ivory ring of hind tibia usually indistinct.

Distribution.

As Thomson’s name implies this species is most common in boreo-alpine areas. In northern Europe it is quite widespread and common at higher latitudes and high altitude sites in the southern part, but becoming scarcer towards the southern lowlands in Sweden. Specimens are examined from Austria, Bulgaria, Finland, Germany, Netherlands (den Dolder, de Bilt, Tilburg, Wageningen, Groesbeek, Rhenen, Velp, Maastricht, Drimmelen, Rotterdam, Voerendaal), Norway, Russia, Serbia and Sweden.

Biology.

The species occur in (boreal) landscapes dominated by coniferous forests where it can be locally common. Many of the sites in Scandinavia are at high altitude. Gasteruption boreale is lacking from more open localities as well as in regions dominated by deciduous forests. It has been observed searching high stumps of Pinus trees and it also attends old wooden walls and artificial bee nests in gardens. Probably it is a kleptoparasitoid of Hylaeus spp.