Description of the female of Platycheirus altomontis Merlin & Nielsen in Nielsen, 2004 (Diptera, Syrphidae) with notes on the occurrence and hilltopping behaviour of rare French montane and Alpine Syrphidae Author Van de Meutter, Frank https://orcid.org/0000-0002-9850-1860 Research Institute for Nature and Forests (INBO), Achterheide 16, 3980 Tessenderlo, Belgium frank.vandemeutter@inbo.be text Alpine Entomology 2022 2022-09-19 6 65 76 http://dx.doi.org/10.3897/alpento.6.81676 journal article http://dx.doi.org/10.3897/alpento.6.81676 2535-0889-6-65 69D24E57CCA84B1089541986CD071C70 5D0B91EC5F8C526FA9695E6490F98BF4 Platycheirus altomontis Merlin & Nielsen in Nielsen, 2004 Examined material. FRANCE • 1 female , 05- Hautes-Alpes , Molines-en-Queyras , near Pain de Sucre , 44.698°N , 6.991°E , 2780 m , 26 Jul. 2020 ; 3 males , 2 females , 05-Hautes-Alpes, Vars, La Mortrice, 44.574°N , 6.769°E , 3142 m , 27 Jul. 2020 . Two high mountain tops were searched and both produced P. altomontis . A female was found feeding on small white flowers near the top of the Pain de Sucre, and 3 males and 2 females were found on the top of La Mortrice. The females were visiting small flowers, the males were feeding or sitting on the stones, from which they made short flights, suggestive of hilltopping behaviour. The female of P. altomontis is unknown so far and is described below. Females of P. altomontis were identified as such because they occurred together with the males, and because they shared some typical characters also found in the males including the very dark legs, the very broad head, and the very long hairs on the head and thorax. A male P. altomontis is shown in Fig. 1 , the female is shown in Figs 2 - 4 . Figure 1. Habitus dorsal view of a male Platycheirus altomontis , 27.Vii.2020 , Vars, la Mortrice (photo by Sander Bot). Description of the female of P. altomontis . The following description is based on the three collected females. Head (Figs 2 , 3 ): Eyes bare, frons at the height of the antenna distinctly broader than an eye. Third antennal segment (flagellum) 1.2 to 1.6 times longer than wide, dark grey-brown but narrowly orange below at base, scape and pedicel black, arista relatively short and thick, slightly longer than flagellum. Face below the antennae with very long, white pilosity, mainly at the sides, as long or longer as the distance between the posterior ocelli. Face completely covered with thin grey pollinosity, frons and vertex undusted except narrow triangular paired dust spots that each reach one third of the width of the frons. Frons with long white to dark grey pilosity, about as long as the 3rd antennal segment. Facial tubercle and mouth edge distinctly protruding, occiput completely pollinose but denser pollinose on ventral side. Figure 2. Frontal view of the head of a female P. altomontis , 27.Vii.2020, Vars, la Mortrice (photo by Sander Bot). Thorax (Fig. 3 ): Scutum and scutellum shining metallic blue-black with long white pilosity, as long or longer as flagellum. Pleurae and humerus with thin grey pollinosity and rather long white pilosity. Figure 3. Side view of the head and thorax of a female P. altomontis , 27.Vii.2020, Vars, la Mortrice (photo by Sander Bot). Wing: Stigma light yellow. Wing covered with microtrichia, except cell bm, br and cua microtrichose apically, otherwise bare. Calypter yellow-white, haltere yellow-brown. Legs: All legs completely dark with thin grey pollinosity, but tibiae narrowly yellow at base and femora yellow at their distal end. Legs entirely pale-haired. Coxae and trochanters of usual shape. Abdomen (Fig. 4 ): Relatively short and broad, tergites 2 and 3 more than 2 times broader than long. Abdomen dark grey-black, largely matt except large shining areas in the frontal corners at the sides of all tergites. Tergites 3 and 4 on these shining areas with large semi-rectangular spots of white-grey pollinosity with rounded inner corners, covering somewhat more than half the length of the median axis of the tergite. Pilosity on abdomen pale; sparse, short and adpressed centrally, long and erect laterally. Pilosity on sternites pale. Pilosity on s1-2 very long and erect, on 3-5 short and adpressed. Figure 4. Dorsal view of the abdomen of a female P. altomontis , 27.Vii.2020, Vars, la Mortrice (photo by Sander Bot). Body length: 6-7 mm. Of the 23 species in the Platycheirus ambiguus group, the females are as yet unknown for 8 species. In the key for females of Nielsen (2014) the female of P. altomontis would run to P. lundbecki (Collin, 1931). No material of P. lundbecki females was available to me to compare with, therefore no differential diagnosis relative to that species is provided. Based on current knowledge of the distribution of the species, the area of origin may be decisive for deciding which species is involved (Nordic countries: P. lundbecki , high Alpine mountain tops: P. altomontis ). From all other known species of the P. ambiguus group the female of P. altomontis differs by the rather small, compact build with short and broad, black abdomen with grey dust spots and very dark legs. The female resembles the male of P. altomontis apart from the usual sexual dimorphism found within this genus. Additional records and observations of rare and new syrphids from the French mountains All expeditions combined, a total of 205 species of Syrphidae have been observed in mountains in France by the author (see Suppl. material 1). Of these, two species are new to France and 26 species occur in 5 or less French departments based on Speight et al. (2018) and may be considered rare in the French context. Below an alphabetically ordered account of these rare and new species recorded in France is given. If applicable, details on ecological observations are provided. All records are leg. and coll. F. Van de Meutter and are from France, unless otherwise stated. For each location, the department with its number (if in France), the height above sea level in meters, and decimal coordinates (WGS84) are provided. Observations are annotated with behavioural observations mainly regarding hilltopping. Cheilosia crassiseta Loew, 1859 Examined material. FRANCE • 1 male, 05-Hautes-Alpes, Villar-d'Arene , Col du Lautaret, 45.029°N , 6.401°E , 2075 m, 21 Jun.2020; 2 males, 05-Hautes-Alpes, Molines-en-Queyras, near Pain de Sucre, 44.698°N , 6.991°E , 2780 m, 26 Jul. 2020; 2 males, 5 females, 05-Hautes-Alpes, Vars, near La Mortrice, 44.574°N , 6.760°E , 2844 m, 27 Jul. 2020. Cheilosia marginata (Becker, 1894) Examined material. FRANCE • 2 males, 05-Hautes-Alpes, Villar-d'Arene , Col du Lautaret, 45.029°N , 6.401°E , 2075 m, 21 Jun. 2020. Cheilosia pascuorum Becker, 1894 Examined material. FRANCE • 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 1780 m, 44.623°N , 6.716°E , 20 Jun. 2020. Dasysyrphus postclaviger (Stys & Moucha, 1962) Examined material. FRANCE • 2 females, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.623°N , 6.716°E , 1780 m, 20 Jun. 2020; 1 male, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.613°N , 6.743°E , 2010 m, 24 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.621°N , 6.721°E , 1792 m, 24 Jun. 2020. Eristalis alpina (Panzer, 1798) Examined material. FRANCE • 1 male, 07- Ardeche , Lafarre, 45.058°N , 4.496° E, 550 m, 4 Aug. 2021; 1 male, 1 female, ibidem, 6 Aug. 2021. Notes. Previously only known from one department in the Alps. On observation.org, however, a female E. alpina has been reported from Central France by Menno Reemer at Valcivieres , indicating more populations or a metapopulation may be present in the mountainous of the south-central part of France. Melangyna barbifrons ( Fallen , 1817) Examined material. FRANCE • 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.611°N , 6.743°E , 2140 m, 20 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.605°N , 6.766°E , 2280 m, 22 Jun. 2020. Both specimens were caught on flowering Salix sp.. Melangyna quadrimaculata (Verrall, 1873) Examined material. FRANCE • 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.605°N , 6.766°E , 2280 m, 22 Jun. 2020. On flowering Salix sp.. Melangyna ericarum (Collin, 1946) Examined material. FRANCE • 1 male, 05-Hautes-Alpes, la Danchere , path to Lac Lauvitel, 1180 m, 44.982°N , 6.072°E , 25 Jul. 2019; 2 males, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.614°N , 6.746°E , 1950 m, 20 Jun. 2020; 1 male, 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.611°N , 6.743°E , 2140 m, 20 Jun. 2020; 1 female, 05-Hautes-Alpes, Freissinieres , 44.712°N , 6.447°E , 2050 m, 23 Jun. 2020; 1 female, 05-Hautes-Alpes, Cervieres , Le Laus, 44.849°N , 6.735°E , 1805 m, 25 Jun. 2020. Notes. This species is poorly described in current literature but can be identified with Speight and Sarthou (2015) . Possibly overlooked to some extent. Males were observed hovering above forest tracks in pine wood. Merodon atratus (Oldenberg, 1919) Examined material. FRANCE • 3 females, 05-Hautes-Alpes, la Berarde , parc des Ecrins, 44.905°N , 6.316°E , 1910 m, 23 Jul. 2019; 3 males, 1 female, 05-Hautes-Alpes, la Grave, Le Chazelet, plateau des Emparis, 44.905°N , 6.332°E , 1800 m, 23 Jul. 2019; 1 male, 05-Hautes-Alpes, Molines-en-Queyras, vers col d'Agnel , 44.713°N , 6.919°E , 2090 m, 26 Jul. 2020; 2 males, 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.608°N , 6.731°E , 2345 m, 27 Jul. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.616°N , 6.723°E , 1825 m, 27 Jul. 2020. Merodon cinereus (Fabricius, 1794) Examined material. FRANCE • 2 females, 05-Hautes-Alpes, la Berarde , parc des Ecrins, 44.905°N , 6.316°E , 1910 m, 8 Jul. 2005; 1 female, 05-Hautes-Alpes, Molines-en-Queyras, vers col d'Agnel , 44.713°N , 6.919°E , 2090 m, 26 Jul. 2020; 1 male, 05-Hautes-Alpes, Molines-en-Queyras, vers col d'Agnel , 44.700°N , 6.946°E , 2290 m, 26 Jul. 2020; 3 males, 4 females, 05-Hautes-Alpes, Molines-en-Queyras, vers col d'Agnel , 44.692°N , 6.971°E , 2576 m, 26 Jul. 2020; 1 male, 05-Hautes-Alpes, Villar d'Arene , Col du Lautaret, 45.033°N , 6.403°E , 2050 m, 28 Jul. 2020; 1 male, 2 females, 07- Ardeche , Saint-Martial, Gerbier de Jonc, 44.843°N , 4.195°E , 1430 m, 6 Aug. 2021; 1 male, 1 female, 07- Ardeche Saint-Martial, 44.866°N , 4.195°E , 1400 m, 6 Aug. 2021. Merodon parietum Wiedemann in Meigen, 1822 Examined material. FRANCE • 1 male, 2 females, 09-Ariege, Bordes-Uchentein, Maison du Valier, 42.808°N , 1.049°E , 1380 m, 14 Jul. 2020. Paragus absidatus Goeldlin, 1971 Examined material. FRANCE • 2 males, 1 female, 05-Hautes-Alpes, la Grave, Le Chazelet, plateau des Emparis, 44.905°N , 6.332°E , 1800 m, 24 Jul. 2019. Parasyrphus kirgizorum (Peck, 1969) / P. tarsatus (Zetterstedt, 1836) Examined material. FRANCE • 5 males, 10 females, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.611°N , 6.743°E , 2140 m, 20 Jun. 2020; 5 males, 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.603°N , 6.759°E , 2320 m, 22 Jun. 2020; 1 male, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.613°N , 6.743°E , 2010 m, 24 Jun. 2020. Notes. In the Alps a long series of Parasyrphus was collected (Figs 5 , 6 ), which clearly belong to the same species, but which cannot unambiguously be identified with current literature, displaying features of P. kirgizorum and P. tarsatus . The specimens are large (11-14 mm), have a clear orange underside of the third antennal segment, and large, black triangular marks on the sternites (Fig. 6 ). For now, they are left unidentified but for future reference, pictures are provided which may allow for identification once stable characters and species delimitations are reformulated (see Figs 5 , 6 ). Found on flowering Salix sp. at the edges of remnant snow patches. On 22.Vi.2020, a group of hilltopping males (>25) was found at the last larch Larix sp. above the treeline at 2320 m. They were sitting on the tree or were hovering close to it. Figure 5. Male Parasyrphus kirgizorum or P. tarsatus , 20.Vi.2020, Vars, Val d'Escreins . Habitus dorsal view with detail of the head (photos by Sander Bot). Figure 6. Male Parasyrphus kirgizorum or P. tarsatus , 20.Vi.2020, Vars, Val d'Escreins . Ventral view of abdomen. Note the dark triangular markings on the sternites (photo by Sander Bot). Pipizella bispina Simic 1987 Examined material. FRANCE • 1 male, 1 female, 05-Hautes-Alpes, la Danchere , path to Lac Lauvitel, 44.982°N , 6.072°E , 1180 m, 25 Jul. 2019. Found sunning on tree leaves in a small clearing within broad-leaved forest. Pipizella elegantissima Lucas, 1976 Examined material. FRANCE • 1 male, 1 female, 38-Isere, Mont-de-Lans, 770 m, 45.009°N , 6.068°E , 19 Jun. 2019. ITALY •: 2 male, 1 female, Oulx, Amazas Torino, 45.009°N , 6.826°E , 1160 m, 25 Jul. 2020. Notes. Pipizella elegantissima was seen at the edge and along paths of broad-leaved forests on the lower, warmer slopes of the Alps, usually flying low through forest margin vegetation. Though it occurs at rather low elevation, it appears to be mountain species that is so far only known from the French and Italian Alps and the Italian Apennines (Speight, 2020). Pipizella speighti Verlinden, 1999 Examined material. FRANCE • 1 male, 09-Ariege, Bordes-Uchentein, Maison du Valier, 42.802°N , 1.056°E , 1760 m, 14 Jul. 2020. Platycheirus brunnifrons Nielsen, 2004 Examined material. FRANCE • 5 females, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.611°N , 6.743°E , 2140 m, 20 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.614°N , 6.746°E , 1950 m, 20 Jun. 2020; 3 females, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.605°N , 6.766°E , 2280 m, 22 Jun. 2020; 7 females, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.613°N , 6.743°E , 2010 m, 24 Jun. 2020; 1 female, 05-Hautes-Alpes, Cervieres , Col d'Izoard , 44.820°N , 6.737°E , 2400 m, 25 Jun. 2020; 1 female, 05-Hautes-Alpes, Molines-en-Queyras, Fontgillarde, 44.718°N , 6.908°E , 2040 m, 26 Jul. 2020. Notes. Platycheirus brunnifrons were always caught on late flowering Salix sp. at the edge of remaining snow patches except for the individual in July that was feeding on a yellow crucifer. The identification of the female P. brunnifrons was based on Nielsen (2014) and corroborated by comparison with a long series of male and female P. brunnifrons from the Caucasus. Platycheirus clausseni Nielsen, 2004 Examined material. FRANCE • 1 male, 65- Hautes-Pyrenees , Bagneres-de-Bigorre , Tourmalet, 42.901°N , 0.158°E , 2010 m, 17 Jul. 2020. Notes. Feeding on a low yellow crucifer on a dry scree slope. Platycheirus complicatus (Becker, 1889) Examined material. FRANCE • 1 male, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.605°N , 6.766°E , 2280 m, 22 Jun. 2020. Platycheirus discimanus (Loew 1871) Examined material. FRANCE • 1 male, 2 females, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.611°N , 6.743°E , 2140 m, 20 Jun. 2020; 2 males, 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.605°N , 6.766°E , 2280 m, 22 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.603°N , 6.759°E , 2320 m, 22 Jun. 2020; 2 males, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.613°N , 6.743°E , 2010 m, 24 Jun. 2020. Platycheirus fasciculatus Loew, 1856 Examined material. FRANCE • 3 males, 1 female, 65- Hautes-Pyrenees , Bagneres-de-Bigorre , Tourmalet, 42.808°N , 0.159°E , 2090 m, 17 Jul. 2020; 1 female, 05-Hautes-Alpes, Molines-en-Queyras, top Pain de Sucre, 44.691°N , 6.999°E , 3140 m, 28 Jul. 2020. Notes. Both in the Alps and the Pyrenees found on scree slopes with sparse vegetation. A male is shown in Fig. 7 . Figure 7. Habitus dorsal view of male Platycheirus fasciculatus , 17.Vii.2020, Bagneres-de-Bigorre , Tourmalet (photo by Sander Bot). Platycheirus sticticus (Meigen, 1822) Examined material. FRANCE • 1 female, 31-Haute-Garonne, Portet-d'Aspet , 42.941°N , 0.858°E , 1025 m, 11 Jul. 2020. Platycheirus tatricus Dusek & Laska , 1982 Examined material. FRANCE • 1 female, 05-Hautes-Alpes, La Berarde , parc des Ecrins, 44.905°N , 6.316°E , 1910 m, 7 Jul. 2005; 1 female, 05-Hautes-Alpes, La Berarde , parc des Ecrins, 44.905°N , 6.316°E , 1910 m, 23 Jul. 2019; 1 male, 2 females, 05-Hautes-Alpes, Villar d'Arene , Col du Lautaret, 45.026°N , 6.406°E , 2220 m, 21 Jun. 2020; 9 males, 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.603°N , 6.759°E , 2320 m, 22 Jun. 2020; 1 male, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.605°N , 6.766°E , 2280 m, 22 Jun. 2020; 1 female, 05-Hautes-Alpes, Freissinieres , 44.712°N , 6.447°E , 2050 m, 23 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.613°N , 6.743°E , 2010 m, 24 Jun. 2020; 1 female, 09-Ariege, Bordes-Uchentein, Maison du Valier, 42.802°N , 1.056°E , 1760 m, 14 Jul. 2020; 2 females, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.608°N , 6.731°E , 2345 m, 27 Jul. 2020. Notes. On 22.Vi.2020, a group of hilltopping males (>25) was found at the last larch Larix sp. above the treeline at 2320 m. Rohdendorfia alpina Sack 1938 NEW TO FRANCE Examined material. FRANCE • 17 males, 11 females, 05-Hautes-Alpes, Molines-en-Queyras, near Pain de Sucre, 44.698°N , 6.991°E , 2780 m, 26 Jul. 2020; 7 females, 05-Hautes-Alpes, Vars, near La Mortrice, 44.574°N , 6.760°E , 2844 m, 27 Jul. 2020; 3 males, 1 female, 05-Hautes-Alpes, Vars, top La Mortrice, 44.574°N , 6.769°E , 3142 m, 27 Jul. 2020. Notes. A species of bare scree slopes at high altitude. Though this species was never seen before in France, it is very common locally. The numbers listed above are only a fraction of the numbers seen in the field. Rohdendorfia alpina was found at both of the two high mountain tops visited in July 2020 and probably is present at many other mountain tops in the French Alps. At La Mortrice, male R. alpina seemed to perform hilltopping behaviour. A male and a female are shown in Figs 8 , 9 . Figure 8. Habitus dorsal view of male Rohdendorfia alpina , 26.Vii.2020, Molines-en-Queyras, near Pain de Sucre (photo by Martin Speight). Figure 9. Habitus dorsal view of female Rohdendorfia alpina , 26.Vii.2020, Molines-en-Queyras, near Pain de Sucre (photo by Martin Speight). Spazigaster ambulans (Fabricius, 1798) Examined material. FRANCE • 1 male, 1 female, 05-Hautes-Alpes, Molines-en-Queyras, vers col d'Agnel , 44.700°N , 6.946°E , 2290 m, 26 Jul. 2020; 1 male, 1 female, 05-Hautes-Alpes, Molines-en-Queyras, vers col d'Agnel , 44.713°N , 6.919°E , 2090 m, 26 Jul. 2020. Sphaerophoria estebani Goeldlin, 1991 Examined material. FRANCE • 3 males, 05-Hautes-Alpes, La Berarde , parc des Ecrins, 44.904°N , 6.332°E , 2400 m, 23 Jul. 2019. Notes. All individuals were caught on a patch of disturbed and slightly fertilized patch of ground next to a refuge building with sparse pioneer vegetation of yellow crucifers. In the nearby more pristine habitat other Sphaerophoria species were found. It is the experience of the author, that many of the species of the Sphaerophoria rueppellii -group are linked to disturbed situations with pioneer vegetation: S. rueppellii in open lowland situations (ground works, riparian zone of streams, ... ) S. shirchan in recent forest clearings, and S. estebani in high mountain areas (scree slopes, human disturbances, ... ). Syrphocheilosia claviventris (Strobl, 1910) Examined material. FRANCE • 2 males, 1 female, 05-Hautes-Alpes, Villar-d'Arene , Col du Lautaret, 45.029°N , 6.401°E , 2075 m, 21 Jun. 2020; 1 female, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.605°N , 6.766°E , 2280 m, 22 Jun. 2020; 1 female, 05-Hautes-Alpes, Freissinieres , 44.704°N , 6.435°E , 2240 m, 23 Jun. 2020; 2 females, 05-Hautes-Alpes, Molines-en-Queyras, vers col d'Agnel , 44.692°N , 6.971°E , 2576 m, 26 Jul. 2020. Xylota triangularis Zetterstedt, 1838 Examined material. FRANCE • 1 male, 05-Hautes-Alpes, Vars, Val d'Escreins , 44.614°N , 6.746°E , 1950 m, 20 Jun. 2020. Hilltopping at montane and Alpine hilltops During the above-mentioned visits to the French Alps, 13 species were observed hilltopping. Raw estimates of numbers and altitude at which the behaviour was performed are indicated in Table 2 . Table 2. Overview of the species observed hilltopping in the French Alps in June and July 2020. The estimated number of individuals and the elevation(s) (in m asl) of the hilltop(s) are indicated.

Species	Nr. (males)	Elevation (m asl)	Month
Cheilosia canicularis (Panzer, 1801)	15	2345	July
Cheilosia melanura (Becker, 1894)	25	2320	June
Didea alneti (Fallen, 1817)	2	2320	June
Epistrophe leiophthalma (Schiner & Egger, 1853)	1	3142	July
Eristalis tenax Linnaeus, 1758	3	3142	July
Eupeodes flaviceps (Rondani, 1857)	2	3142	July
Parasyrphus kirgizorum (Peck, 1969) / Parasyrphus tarsatus (Zetterstedt, 1838)	25	2320	June
Pipizella calabra (Goeldlin, 1974)	25	2320	June
Pipizella nigriana ( Seguy , 1961)	30	2320	July
Pipizella pennina (Goeldlin de Tiefenau, 1974)	2	2320	June
Platycheirus altomontis Merlin & Nielsen in Nielsen, 2004	3	3142	July
Platycheirus tatricus Dusek & Laska , 1982	25	2320	June
Rohdendorfia alpina Sack, 1938	25	2780/3142	July