Several of the type specimens are quite damaged and many characters are difficult or impossible to observe (Figs 1–2). However, it is obvious that they do not belong to Gymnometriocnemus, and the better preserved male specimens show characters that fits the diagnosis of Chaetocladius: wings with coarse punctuation and without macrotrichia on the membrane (Fig. 1D), divergent lateral spinules on the tibial spurs (Fig. 1C) and a fore leg ratio of 0.75. We are confident that this species should be placed in Chaetocladius, but due to the state of the specimens and the unrevised nature of the genus, we have not attempted to compare C. volitans with other species in Chaetocladius.

We have only seen two females from eastern and central Norway. The two specimens fit Edwards’ description for G. brevitarsis and represent the first records of this species in Norway. The wing and antenna are photographed (Fig. 3A, B) and leg ratios of fore- mid- and hind legs are measured to be LR₁ 0.41-0.42 [n=2], LR₂ 0.38-0.39 [n=2], LR₃ 0.50-0.53 [n=2] respectively. Only females are known and partial COI gene sequences do not reveal close relationships to any other species in Gymnometriocnemus. Subgeneric placement of G. brevitarsis is therefore not possible.

Only one specimen of this species from Norway has been available to us. It fits Sæther’s description of G. (G.) marionensis in having very slightly larger megasetae on the gonostyli than specimens of G. (G.) subnudus (Figs 4A, C), but this character is not trustworthy as it is dependent on the orientation of the gonostyli in the slide-mount. The larger anal point will separate G. (G.) marionensis (c. 38 µm long) from G. subnudus (c. 17 µm long). Cranston and Oliver (1988) synonymized G. (G.) marionensis with G. (G.) subnudus doubting the diagnostic value of the size of the megaseta and position of the end of R₂₊₃ (Fig. 5A). We have not examined the types of G. (G.) marionensis, but specimens from Michigan and North Carolina (ZMBN) identified by Ole Sæther as belonging to this species. This record of the species is the first from Norway and Europe.

Holotype: Male adult (NTNU-VM slide 143840), Norway, Hordaland, Kvam, Berge, oak canopy fogging, tree #3, 60.30921°N; 6.16453°E, 23.vi.2011, leg. Karl H. Thunes [BOLD ID: CH-eik131]. 5 Paratypes: 2 male adults as holotype except tree #1 60.314°N; 6.167°E, 21.vi.2011; 1 female adult as holotype except tree #18, 59.201°N; 9.920°E, 5.vii.2012; 2 male adults, Norway, Telemark, Porsgrunn, Brevik, Frierflauene, 59.0579°N; 9.66485°E, Malaise trap, 30.vi–27.vii.2010, leg. Geir Søli.

The species is named “pallidus”, Latin adjective meaning pale, referring to the conspicuous pale body colour compared to other Holarctic Gymnometriocnemus.

Gymnometriocnemus (G.) pallidus can be separated from other Gymnometriocnemus species by the following combination of characters in the adults: body pale yellow-green; male with short inconspicuous virga, gonostylus with convex outer margin and weakly developed crista dorsalis. Female with setae on most of wing surface, including numerous in cell m; antenna with apical flagellomere pointed and longer than flagellomere 4; genitalia with long rami, about the same length as notum.

Male adult (n = 5 unless otherwise stated). Wing length 1.21–1.30, 1.28 mm. Colouration pale yellow-green body, legs and antennae; slightly darker bands on scutum; postnotum, dorsal side of head, ventral part of preepisternum pale brown; eyes dark brown.

Head. Antennal ratio in Table 1. Temporal setae 9-10; palp lengths (in µm): 25/30/90-100/80-90 (4)/110-115 (4).

Thorax. Antepronotum with 2-6, 3 setae. Dorsocentrals 10-17, 13; acrostichals 7-12, 10, minute and difficult to discern; prealars 3-4; scutellars 6-7.

Wing (Fig. 5B). Costa moderately extended, not reaching half way to apex of M₁₊₂; R₂₊₃ approaching costa at 1/3 distance between R₁ and R₄₊₅. Macrotrichia present on membrane in apical half of wing, 0-2 setae in cell m. Veins Sc, R₂₊₃, M and pseudovein without setae.

Legs. Fore tibia with one spur, 35 µm long; mid tibia with two spurs ca. 20-25 µm long; hind tibia with well-developed comb and 2 spurs, ca. 20 and 35 µm long. Fore leg ratios in Table 1.

Hypopygium (Fig. 4B). Ninth tergite with 10-15, 13 setae, median setae stronger and situated on an obvious anal point. Virga 15–20 µm long consisting of two spines. Inferior volsella well-developed lobe; gonostylus with slightly convex outer margin.

Female adult (n = 1). Wing length 1.23 mm. Colouration as male.

Head. Antenna (Fig. 3E) with five flagellomeres, lengths (in µm): 75/60/70/60/70. Temporal setae 9; palp lengths (in µm): 25/30/95/-/-.

Thorax. Antepronotum with 6 setae. Dorsocentrals 18; acrostichals 11; prealars 3; scutellars 6.

Wing (Fig. 3D). Costa well extended, reaching slightly past half way to apex of M₁₊₂; R₂₊₃ approaching costa at 1/3 distance between R₁ and R₄₊₅. Macrotrichia present on membrane in whole wing. Veins M, Sc and R₂₊₃ without setae.

Legs. Fore tibia with one spur, 20 µm long; mid tibia lost; hind tibia with well-developed comb and 2 spines, ca. 35–40 µm long. Tarsus of fore leg lost (LR₁ not measurable).

Genitalia (Fig. 3F). Gonocoxite IX with 7 setae. Ninth tergite undivided, semi-circular with 12 setae; cercus 50 µm long; seminal capsules about 70 µm long and 45 µm wide, seminal tubules about 325 µm long. Notum as long as rami, 87 µm. Inner lobe of gonapophysis VIII broadly rounded with numerous long medially directed microtrichiae.

Immature stages unknown

The species is morphologically similar to G. (G.) subnudus and G. (G.) johanasecundus, but paler (see whole specimen figures in BOLD dataset DS-GYMNO). Males and females are almost completely yellow-green with pale brown posterior side of head and postnotum; pale brown scutal bands and ventral side of preepisternum. Gymnometriocnemus (G.) pallidus is also similar to these species in having a short, triangular anal point and a small virga, but the hypopygium of G. (G.) pallidus has a more prominent inferior volsella than G. (G.) johanasecundus and considerably stronger anal tergite setae than G. (G.) subnudus (Figs 4B, C). Comparison with DNA barcode data in BOLD indicates that the species also has records from Germany and France.

We have seen specimens from eastern and central Norway that fit well with the original and later descriptions of the species, except for having a lower AR (1.0-1.1) compared to what Edwards (1929) reported. The specimens group in a well-defined barcode cluster (Fig. 6) separated from G. (G.) marionensis and G. (G.) pallidus sp. n. and is fairly widely distributed throughout Europe.

Holotype: Male adult (NTNU-VM slide no. 136299), Norway, Finnmark, Porsanger, small pond near Gaggavann, 69.8306°N; 25.1856°E, 107 m a.s.l., 03.ix.2010, leg. Alyssa Anderson [BOLD ID: Finnmark201]. 3 Paratypes, male adults: 1 Norway, Finnmark, Vardø, Nedre Domen, lake and pond at road E75, 70.3215°N; 31.0341°E, 120 m a.s.l., 05.ix.2010, leg. Alyssa Anderson; 1 Norway, Finnmark, Nordkapp, Nordkapp-Plateau, 71.1446°N; 25.7641°E, 220 m a.s.l., 01-ix-2010, leg. Trond Andersen; 1 Norway, Oppland, Dovre, Rondane National Park, Vidjedalsbekken (upper), Malaise trap, 61.9717°N; 9.83606°E, 1280 m a.s.l., 15.ix.2008, leg. Terje Hoffstad.

The species is named “autumnalis”, Latin adjective meaning belonging to autumn, referring to the time of the year when the type material was collected.

Gymnometriocnemus (R.) autumnalis can be separated from other Gymnometriocnemus species by the following combination of characters in the adult male: body brown, dark brown; virga long and conspicuous with strong lateral sclerotization, anal tergite without dorsal anal point or ridge, gonostylus with convex outer margin and well-defined median crista dorsalis.

Male adult (n = 4 unless otherwise stated). Wing length 1.30–1.52, 1.43 mm. Colouration completely brown, dark brown except for pale transverse bands posteriorly on abdominal tergites V–VIII, narrower on tergite V.

Head. Antennal ratio in Table 1. Temporal setae 8-10, 9; palp lengths (in µm): 25/35/80-90/75-90/105-125.

Thorax. Antepronotum with 2 setae. Dorsocentrals 10-11; acrostichals 8-9, minute and difficult to discern; prealars 4-6; scutellars 2-5.

Wing (Fig. 5D). Costa moderately extended, not reaching half way to apex of M₁₊₂; R₂₊₃ approaching costa at ½ distance between R₁ and R₄₊₅. Macrotrichia frequent on membrane in apical 1/3 of wing, absent from cell m, few (0-6) in cells cu+an. Veins Sc, R₂₊₃, M, Cu, PCu and pseudovein without setae.

Legs. Fore tibia with one spur, 40 µm long; mid tibia with two spurs ca. 20 µm long; hind tibia with well-developed comb and 2 spines, ca. 50 µm long. Fore leg ratios in Table 1.

Hypopygium (Fig. 4D). Ninth tergite with 16-19, 18 setae, without anal point or ridge. Virga 110-120, 115 µm long consisting of two spines, with strong lateral sclerotization. Inferior volsella well-developed lobe; gonostylus with slightly convex outer margin and well-defined median crista dorsalis.

Female and immature stages unknown.

The species is morphologically similar to G. (R.) brumalis and G. (R.) kamimegavirgus, but different in lacking an anal point or ridge on the anal tergite. This character is similar to characters reported for G. terrestris and G. tairaprimus, but these two species can according to original descriptions be separated by having a higher AR (1.4 in G. terrestris) and a different shape of the superior volsella (Krüger and Thienemann 1941; Sasa and Okasawa 1994). The virga of G. terrestris has not been described, but the species is listed as a member of subgenus Gymnometriocnemus in the World Catalogue of Chironomidae (Ashe and O’Connor 2012). We have examined two males and one female between cellophane strips on two separate pins from the Goetghebuer collection; labels reading “Allemagne, Dr Thienemann, Bonn 1939”. Only one pin with a female bears a type label, but all specimens are likely part of the type series and regarded as syntypes. A small virga is visible in a rather well mounted and cleared hypopygium on one of the specimens. We can confirm placement in subgenus Gymnometriocnemus and that none of the specimens we have collected in Norway belong to this species. G. (R.) autumnalis has so far only been recorded from the very north of mainland Norway and the Rondane mountains (1280 m a.s.l.) in Central Norway.

We have barcoded specimens from eastern, central and northern Norway that fall within the same genetic cluster although with quite large intraspecific divergence (0–6.8%, mean 3.42% K2P-distance) (Fig. 6). We are at present not able to find morphological differences that fully correspond to the internal groupings inside the G. (R.) brumalis cluster and all our specimens fit the description by Sæther (1983) with the additions by Cranston and Oliver (1988). There is some variation observed in the length of the virga in relationship with the length of the gonocoxite, one of the characters used to separate G. (R.) acigus from G. (R.) brumalis (Cranston and Oliver 1988; Sæther 1983), but we have not examined or barcoded a sufficient number of specimens to confidently conclude if the divergent genetic clusters in our G. (R.) brumalis can be regarded as separate species. We have examined the male holotype and a male paratype of G. (R.) acigus and can confirm that the species fits our and Cranston and Oliver’s (1988) interpretation of G. (R.) brumalis. The species has a Holarctic distribution.

Gymnometriocnemus (R.) kamimegavirgus can be separated from other species of the genus Gymnometriocnemus by having well-developed, long virga (about the length of the gonocoxite); AR 0.9-1.1 (n=5); LR₁ about 0.53-0.56 (n=3); wing membrane with setae at the apex only, occasionally with 1-2 setae proximally in cell an; R₂₊₃ situated in the middle between R₁ and R₄₊₅; dark brown almost blackish thorax and head, slightly paler abdomen and legs.

Our examined material is from eastern, central and northern Norway, frequently collected near streams, rivers and moors. Male adults fit well with Brundin’s description of G. volitans, and Sasa & Hirabayashi’s description of G. kamimegavirgus except for slightly fewer setae on the abdominal tergites (Brundin 1956; Sasa and Hirabayashi 1993; Sasa and Okasawa 1994). The species is Holarctic in distribution.