Chamaepsila withersi sp. nov.

urn:lsid:zoobank.org:act: 64D2DCA8-1E59-4532-864D-3955D94A1A51

(Figs. 1–9)

Examined material (34♂ & 10♀). HOLOTYPE: male (Fig. 1–3), FRANCE, Isère, RNHC, Crolles, Malaise trap n°117 (Fig. 4), 45.3203916°N 5.8584492°E, 1756 m asl, 3.ix.2019, rec. and leg. Suzanne Foret, coll. MHNG pinned and terminalia preserved in microvial in glycerine. PARATYPES: same data as holotype but: Chapareillan, Malaise trap n°115, 45.4518053°N 5.9294529°E, 1768 m asl, 1♀, 08.viii.2019, Crolles, Malaise trap n°127, 45.3202600°N 5.8579572°E, 1755 m asl, 1♀, 10.vii.2020, Malaise trap n°128, 45.3202943°N 5.8552002°E, 1776 m asl, 1♂, 01.viii.2020, preserved in ethanol 70%, coll. JC; Crolles, Malaise trap n°118, 45.3197377°N 5.8572407°E, 1762 m asl, 3♂, 1♀, 22.vii.2019, Malaise trap n°127, 6♂, 4♀, 10.vii.2020, 9♂, 01.viii.2020, preserved in ethanol 70%, coll. BT; Crolles, Malaise trap n°127, 1♀, 01.viii.2020, Chapareillan, Malaise trap n°126, 45.4518756°N 5.9298663°E, 1750 m asl, 1♂, 22.vii.2020, pinned and terminalia preserved in microvial in glycerine (coll. MHNG), Hautes Alpes, Cervières, near the Col de l’Izoard, net, 44.820893°N 6.7142732363°E, 2400 m asl, 7♂, 1♀, 1.viii.2023, rec. and leg. CL, coll. CL, 7♂, 1♀, 1.viii.2023, coll. JC, label “Col du Galibier, Hautes Alpes”, 2600 m asl, 1♂ (n° 47055017), 16.vii.1911, rec and leg. Claudius Côte, coll. MHNL.

Description. MALE. Body length: 6-7 mm. Head. Ground colour yellow. Ocellar triangle brown to black. Antenna yellow, including postpedicel, which is twice as long as wide at base.Arista yellow, conspicuously thickened and brown at the base, covered with yellow fine rays. Pilosity almost as long as the diameter of the arista at its widest point. The eye is ovoid, 1.1 times higher than large, and 1.4 times higher than the gena. Face yellow. Palpi yellow, brownish at apex. Prelabrum brown. Genae yellowish. Occiput yellowish. Chaetotaxy (all setae black): 3 vertical setae (1 inner vertical seta and 2 outer vertical setae); 1 postocellar seta; 1 to 2 fronto-orbital setae (rarely 3). Thorax. Ground colour yellow; scutum with two black post-sutural stripes. Scutellum yellow. Postnotum yellow with a black spot. Notopleural line vaguely marked, brownish. Pleura entirely yellow, except for a brown spot on the anepimeron, which is bare. Postpronotal lobes yellow. Chaetotaxy (all setae black): 1 notopleural seta; 1 supra-alar seta; 1 post-alar seta; 1 dorsocentral seta; 1 apical scutellar seta. Abdomen. Yellow to brown, with yellow pilosity. Legs: yellow with yellow to brown pilosity. Tarsi brown due to dense pilosity. Wing: Length: 5 mm, infuscate along veins. Veins yellow in the third basal, brown in distal two-thirds. Haltere white. Genitalia (Figs. 5–6). Genital measurement: 0.65 mm lenght in ventral view. The phallus is triangular and pointing downwards. Postgonites are triangular with rounded corners. Just like the others European Chamaepsila, the base of the phallopodeme lies at the postgonites. The hypandrium is very long and does not enclose the phallopodeme.

FEMALE. As in male, but terminalia not studied.

Etymology. The new species is named after Phil Withers, as a tribute to our dipterist colleague and friend who passed away much too soon (Claude 2021). We would have loved to publish these discoveries with him. Specific epithet in genitive case.

Ecology. Adult habitat. In Chartresuse: Malaise trap have been caried out in Subalpine grassland: Seslerion caeruleae & karstic mountain pine savanna: Erico carneae - Pinion sylvestris, Rhododendro ferruginei - Vaccinion myrtilli (Claude et al. 2020 - Fig. 4).At the Col de l’Izoard, the 14 specimens were collected on Cirsium spinosissimum (L.) Scop. 1769 in several gypsum dissolution funnels in a dry grassland context (Figs. 7-9). These depressions offer a cooler environment, sheltered from the wind. The large depressions over 2 m wide were also visited by CL, without success. At the bottom of the small funnels where C. withersi. was observed, the flora is more developed thanks to the greater accumulation of snow and rain. Carpets of C. spinosissimum develop at the bottom of these funnels, especially upstream where it is cooler. Although no further information is available about the specimen captured by Claudius Côte in 1911, it should be noted that the gology of the Col du Galibier is similar, with the presence of areas similar to those where C. withersi was found by CL on the Col de l’Isoard. In Chartreuse, there are no gypsum dissolution funnels, but in this limestone massif, there are many areas of small, cool depressions sheltered from the wind. C. spinosissimum is not present, however, or is extremely rare. Near the Malaise trap sites, C. acaulon (L.) Scop. 176 is present. This species also remains infrequent. For the moment, it is impossible to deduce whether the specimens observed at Izoard are associated with Cirsium sp. or are in depressions sheltered from the wind. Altitude. 1700-2600 m asl. Phenology. June to August. Larval habitat. Unknown but suspected to live in Cirsium spinosissimum (L.) Scop. 1769, in Alps.

Currently known distribution. France, Auvergne-Rhône-Alpes: Isère (in Chartreuse massif), Provence-Alpes-Côte d’Azur, Hautes-Alpes.

Differential diagnosis. Male. C. withersi has the wings infuscate along the veins (Fig. 3), which distinguishes it from nearly all other species of the genus, but it shares this feature with C. ristolasiensis sp. nov. The diagnostic differences between these two species are discussed below under the description of C. ristolasiensis. It is also close (colour, size and habitus) to C. obscuritarsis (Loew, 1856), but differs in having a single pair of scutellar setae. In case of doubt, the terminalia should be compared with those of C. obscuritarsis (Figs. 19-20). Female. Same as male. Terminalia not studied.