Homotropus hellqvisti, Johansson, Niklas, 2020

Johansson, Niklas, 2020, Additions to the Swedish fauna of Diplazontinae (Hymenoptera: Ichneumonidae) with the descriptions of five new species, European Journal of Taxonomy 724, pp. 70-92 : 72-74

Homotropus hellqvisti sp. nov.

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Figs 2 , 5C

Diagnosis

Homotropus hellqvisti sp. nov. ( Fig. 2 A–B) is similar to Homotropus collinus (Stelfox, 1941) ( Fig. 5D, F ), but is primarily distinguished based on the irregular microsculpture on the 3–7 th tergites ( Fig. 2B ) and the shorter and more weakly excised clypeus ( Fig. 5C ). The new species is also similar to Homotropus melanogaster (Holmgren, 1872) ( Fig. 5E ) from which it differs by the only weakly laterally compressed metasoma (in H. melanogaster the metasoma is strongly compressed, knife-like from the 5 th tergite onwards), the irregular microsculpture on the 3–7 th tergites ( Fig. 2B ), the absence of a subbasal dark spot on the hind tibia and the usually more numerous flagellomeres. Note that while the females of H. melanogaster usually have the mid and hind coxae infuscate, the species sometimes occurs in a colour variety with red hind coxae in Sweden ( Klopfstein 2014b: 68–69) (see Remarks). The number of flagellomeres ranges from 17–19 in H. melanogaster (n = 20) and 19–20 in H. hellqvisti sp. nov. Two of the three known females all have distinct, quite large shoulder marks, while only one of the studied females of H. melanogaster (n = 17) has small and diffuse shoulder marks.

Etymology

The specific epithet hellqvisti (masculine name in genitive case) is derived from the name of one of the collectors of the specimens who revealed the presence of this new species, Sven Hellqvist (Umeå, Sweden).

Type material

Holotype SWEDEN • ♀; Västerbotten, Åselet, Hästholmen ; 65.233° N, 20.414° E; 25 May–19 Aug. 2019; R. Mugerwa Pettersson and S. Hellqvist leg.; Malaise trap in riverside, herb rich, mixed forest; NHRS- HEVA000011635 .

Paratypes SWEDEN • 2 ♀♀; same collection data as for holotype; NHRS-HEVA000011636 , NHRS- HEVA000011637 .

Description

Female

Fore wing length 4.2–4.3 mm. Body length 5.5 mm. Head transverse in anterior view. Inner orbits parallel. Face entirely coriaceous and matt. Clypeus with apical margin bilobed and thin, weakly excised centrally ( Fig. 5C ). Antennae with 19–20 flagellomeres. First flagellomere about four times as long as wide. Apical flagellomeres with multiporous plate sensillae also present ventrally. Head behind eyes slightly narrowed. Temple in lateral view about 0.6 times as wide as compound eye. Mesoscutum matt with fine rugulose microsculpture and very weak punctures dissolving against background. Mesopleuron in lower half irregularly rugulose, in upper half polished, below subtegular ridge with irregular punctures. Metapleuron coriaceous. Propodeum evenly coriaceous without carinae. Coxae coriaceous, matt. Fore wing with areolet closed and vein 3rs-m unpigmented ( Fig. 2A ). Metasoma laterally weakly compressed from the 4 th tergite onwards ( Fig. 2A ), with dense hairs. First tergite stout, slightly longer than wide, evenly coriaceous with a faint indication of longitudinal striae in apical corners. Second tergite evenly coriaceous. Third tergite onwards with fine irregular microsculpture ( Fig. 2B ). Spiracle of second and third tergite above lateral fold. Ovipositor sheath apically rounded.

COLOURATION. Body and head black. Mandibles, palpi, occasionally subtegular ridge, hind corner of pronotum and tegulae whitish. Clypeus yellowish. Pale central face patch absent or diffuse. Yellowish shoulder mark small or absent. Scutellum black. Pterostigma transparent brownish. Legs orange, fore coxae white, basally more or less black. Mid and hind coxae orange. Trochanter and trochantelli yellow except for hind trochanter, which is orange. Tibiae whitish. Fore and mid tibia with yellow apices. Hind tibia with apical 0.25 black and base very narrowly infuscate. Hind tarsi black. Mid and fore tarsi whitish, except for brownish apical segment. Metasoma black.

Male

Unknown.

Remarks

Klopfstein (2014b) noted that some females of Homotropus melanogaster collected in Sweden had orange hind and mid coxae, thereby differing in colour from the nominate form with black coxae. Since both forms also often occurred together at the same localities, they were treated as varieties of the same species. The actual specimens with the red coxae studied by Klopfstein bear a handwritten label “sp. X”. I have studied 5 ♀♀ and 2 ³³ of this form of H. melanogaster (NHRS, SMTP) and it is not conspecific with the species here described and apart from the paler coxae there are no reliable distinguishing characters between the two forms. In the key to the species of Homotropus Förster, 1869 provided by Klopfstein (2014b), Homotropus hellqvisti sp. nov. will run to either couplet 6 together with Homotropus melanogaster or to couplet 8 with H. collinus . For distinguishing characters, see Diagnosis.

Ecology

The three known females were collected by a Malaise trap situated in a herb rich riverside boreal forest dominated by birch Betula spp. along the forest river Byskeälven The area ( Fig. 12 A–B) rests on sandy ground and is periodically flooded. The trap also collected several rarely recorded diplazontines such as Syrphoctonus idari Diller, 1985 , Homotropus melanogaster , Diplazon neoalpinus Zwakhals, 1979 and Syrphophilus asperatus Dasch, 1964 .

Figures

Fig. 2. Homotropus hellqvisti sp. nov., paratype, ♀ (NHRS-HEVA000011637). A. Habitus, lateral view. B. Posterior segments of metasoma.

Fig. 5. A–B. Mesoscutum of female, anterodorsal view. A. Homotropus pallipes (Gravenhorst, 1829). B. Homotropus mugerwai sp. nov., paratype (NHRS-HEVA000011633). C–D. Head, anterior view of female. C. Homotropus hellqvisti sp. nov., paratype (NHRS-HEVA000011637). D. Homotropus collinus (Stelfox, 1941). E–F. Posterior segments of metasoma of female. lateral view. E. Homotropus melanogaster (Holmgren, 1872). F. Homotropus collinus.

Fig. 12. A. Malaise trap at Hästholmen by the forest river Byskeälven. Type locality for Homotropus hellqvisti sp. nov. and Homotropus mugerwai sp. nov. Photo: Roger Mugerwa Pettersson. B. The Natura 2000 area Byskeälven from Marranäsvältan. Photo: Sören Uppsäll, Länsstyrelsen.