Chaoborus flavicans

Chaoborus flavicans (Meigen, 1830)

Corethra flavicans Meigen 1830: 243 (original description). Macquart 1834: 47 (short notes on morphology). Gimmerthal 1845: 296 (short notes on morphology). Giles 1900: 362 (identification key to adults, redescription of the holotype, translation of the original description from German to English). Theobald 1901: 294 (translation of the original description from German to English, reference to Giles 1900). Giles 1902: 505 (identification key to adults, redescription of the holotype, translation of the original description from German to English). Corethra flavicans: Berg 1937: (ecology, morphology, biology), labral blades fig.1.1, mandible fig.1.2., terminal process fig. 1.3, palpus fig 2.4., two last flagellomeres fig. 2.5., paramere fig. 2.6., egg mass fig. 16, embryos fig. 17, egg mass fig. 18. Berg & Petersen 1956: 184 (ecology, morphology), labral blade fig. 74A, mandible fig. 74B, pupal respiratory organs fig. 74C, terminal process fig. 74D, palpus fig. 75A, two last flagellomeres fig. 75B, paramere fig. 75C.

Chaoborus flavicans: Brunetti 1911: 229 (nomenclature). Séguy 1924: 170 (identification key to adults, comparison to C. crystallinus). Séguy 1925: 58 (identification key to adults, comparison to C. crystallinus, distribution, ecology). Martini 1929: 56 (identification key to adults, resdescription, distribution), palpus fig. 77a, two last flagellomeres fig. 77b, parameres fig. 77c & c1. Edwards 1930: 164 (notes on adult morphology, in comparison to C. obscuripes and C. crystallinus). Matheson 1944: 94 (identification key to adults, short notes on morphology), hypopygium plate 10 fig. 2. Sládeček 1952: (larval and pupal morphology, ecology), head fig. 2, mandible fig. 4, labral blade fig. 5c, respiratory organ fig. 7a, terminal process fig. 8a (figs. 5, 7,8 copied from Peus 1934). Aitken 1954: 442 (key to larva, pupa and adult, distribution in Sardinia), labral blade fig. 1.1. Prokešová 1959: (larval morphology, instars, ecology), head capsule fig. 7, mandible fig. 8, thorax fig. 10. Hirvenoja 1961: (identification key). Brindle 1962: (identification key to larvae, ecology), mandible fig. 6. Stahl 1966b: (tentative synonymy of C. alpinus with C. flavicans). Saether 1967: forma flavicans, forma alpinus, forma infuscatus (morphology, intraspecific variation), labral blades fig.1A, bifurcate labral setae fig.1 B-E, bristled labral scales fig. 1F-H, plumose labral seta fig. 1J, maxilla fig. 1K, labrum fig. 1L, tergites of pupal exuviae fig. 2A-B, parameres fig. 2C-F. Parma 1969: (larval instars, morphology, ecology, identification key), labral blades fig. 3M-O, labral setae fig. 4B, bifurcate setae fig. 5A-C, bristled scales fig. 6A-F, scales of anal apparatus fig. 7A-C, setae above anal gills fig. 7D-E, anal fan seta fig. 7F, dorsal process fig. 7K, anal papillae fig. 7N, mandible fig. 7O. Parma 1971a: (biology, ecology), embryo fig. 12, newly hatched larvae fig. 13. Parma 1971b: (morphology of larval instars), head capsule, antenna, prelabral appendage, mandible, maxilla, dorsal process fig. 1, last abdоminal segments, bristled scales of the labrum, bifurcate setae of the labrum, middle seta of dorsal side of head capsule, details of anal apparatus fig. 2. Balvay 1977a: (identification key, larval instars), labral blade fig. 1C.F., dorsal process and anal tubules fig. 2C.F., mandible fig. 3C.F. Balvay 1977b: (morphometry of larval instars). Balvay 1977c: (morphology of head and mandibles of larval instars), head 1 st instar larva fig. 1, post antennal setae 1 st instar larva fig. 2a, 4 th instar larva fig. 2b, placement of post antennal setae 2 nd instar larva fig. 3a, 4 th instar larva fig. 3b, mandible 1 st instar larva fig. 4, mandible 2 nd instar larva fig. 5, mandible 3 rd instar larva fig. 6, mandible 4 th instar larva fig. 7. Stenson 1978: (ecology), outline of larval head fig. 1. Borkent 1979: (discussion of characters, number of anal fan setae and head capsule length of 4 th instar larvae). Stenson 1980: (ecology), head outline fig. 2. Uutala 1990: (paleolimnology, identification key), mandibles fig. 4-5. Wagner 1990: 72 (list of species). Borkent 1993: 15 (list of species, synonymous names, locations of type specimens, distribution). Walker 2001: 46 (paleolimnology), mandible fig. 1e. Berendonk et al. 2003: (molecular phylogeny in relation to body size and lake vs. pond-dwelling lifestyle). Sweetman & Smol 2006: (paleolimnology), mandible fig. 3C. Wende et al. 2006: (molecular phylogeny, haplotypes). Dupuis et al. 2008: (molecular analysis, phylogeny, distribution, ecology, morphology), mandible fig. 2B. An et al. 2012: (molecular phylogeny, emphasis on Korean specimens). Borkent 2014: 476 (list of list of species, synonymous names, locations of type specimens, distribution).

Corethra plumicornis: “søform” Wesenberg-Lund 1914: 8 (ecology, life cycle, morphology of larva and pupa), egg mass fig. 6, larval head (lateral view) fig. 7b, dorsal view fig. 8b, anal fan fig. 9b, labral blade fig. 10b, pupal respiratory organ fig. 11b.

Chaoborus eluthera Dyar & Shannon 1924: 211, syn. (description). Stone in Belkin et al. 1966: 22 (lectotype designation, syn. of C. flavicans).

Chaoborus (Chaoborus) elethera: Edwards 1932: 25 (misspelling, list of species).

Chaoborus (Chaoborus) flavicans: Edwards 1932: 26 (list of species). Peus 1934: (larval morphology, identification key, pupal morphology), mandible fig. 3b, terminal process fig. 9a, apex of respiratory organ fig. 10c. Monchadskii 1936: 114 (identification key, notes on larval morphology), figures copied from Peus 1934. Cook 1956: 23, in part (redescription of C. flavicans includes both C. flavicans and C. albipes), male abdominal tergites 3 and 4 fig. 14B. Enns 1960: 128 (key to larvae, faunistics), labral blade fig. 9 (may also refer to C. albipes). Cook 1965: 103 (list of species, distribution). Roth 1967: 65 (identification key to larvae, notes on morphology, ecology), antenna fig. 1.1, dorsal process fig. 1.5, labral blade fig. 1.9, mandible fig. 1.13. Hennig 1968: 73 (list of European species, literature on larvae and pupae). Roth 1968: (identification key to pupae), terminal process fig. 4. Saether 1970: 35 (measurements and ratios of body parts, phylogeny), upper part of eye fig. 15C. Saether 1972: (identification keys to larval, pupal and adult stages, ecology), upper part of eye fig. 10A, parameres fig. 11B-C, respiratory organs fig. 12I-J, terminal process fig. 12O, head outline fig. 13J, dorsal process fig. 13M, mandible fig. 13Q, larval antennal 15C, labral blade fig. 15H. Sikorowa 1973: 31 (larval instars, morphology, ecology), parameres fig. 1, larval antenna fig. 4d, labral blade fig. 9d, egg mass fig. 14. Nilssen 1974: (notes on larval morphology, ecology), mandible fig. 3B. Borkent 1981: 126 (distribution, ecology, phylogeny). Saether 1997a: (identification key to larvae, pupae and adults), figures are the same as in Saether 2002, except female genitalia figures are lacking. Saether 1997b: (subgeneric identification key to larvae, pupae and adults), figures are the same as in Saether 2002, except female genitalia figures are lacking. Saether 2002: 27 (identification key to larva, pupa and adult, redescription, morphometry), parameres fig. 18e-f, female genitalia fig. 19h, respiratory organs fig. 20c-d, larval antenna fig. 21c, labral blade fig. 21h, mandible fig. 21m, dorsal process fig. 21r, anal tubules fig. 21w.

Chaoborus crystallinus ”form aus gr. Madebröken See”: Eckstein 1936: (larval and adult morphology, comparison between European and exotic species), dorsal process fig. 1a, labrum and labral blade fig. 3b, bifurcate seta fig. 4c, bristled scale fig. 5c, labral seta fig. 6d, labral blade fig. 7a, labral blades fig. 8b, paramere fig. 9a.

Chaoborus alpinus Peus 1938: 63, syn. (description, larva, pupa, adult male), mandible fig. 1, labral blades fig. 2, dorsal process fig. 3, terminal process fig. 4, respiratory organs fig. 5d-f, parameres fig. 6. Hirvenoja 1960: (identification of museum specimens, ecology), parameres fig. 3. Hirvenoja 1961: (identification key). Ökland 1964: 131 (ecology, notes on morphology or larva, pupa and adult), labral blade fig. 59A, mandible fig. 59B, terminal process fig. 59C, respiratory organs fig. 59D, parameres fig. 59E. Sikorowa 1966: (larval morphology, ecology), anterior part of head fig. 3. Sikorowa 1967: (larval instars, taxonomy), mandibles fig. 1, paramere fig. 2.

Chaoborus: Alhonen & Haavisto 1969: (paleolimnology of a lake), larval mandible (plate 1, fig. 1).

Chaoboridae: Ursenbacher et al. 2020: (paleolimnology), pupal respiratory organ fig. 2.

Sayomyia albipes: Felt 1904: 363 (in part, description of larva), mandible fig. 103, labral blades fig. 104, labrum fig. 105, ventral hooks fig. 106.

Sayomyia rotundifolia Felt 1904: 366 (in part, description of larva).

Sayomyia flavicans: Theobald 1905: 43 (list of known species).

Material examined. Type material. Holotype male. [“ Corethra flavicans ³”] (handwritten), [“ ISI 40”] (handwritten), [“ MNHN, Paris ED946”], pinned (MNHN). Type locality: Germany (Giles 1902, Borkent 2014). The holotype is pinned, in relatively good condition, tip of abdomen missing. Not studied, high quality photos on labels and specimen available at https://science.mnhn.fr/taxon/species/chaoborus/flavicans.

Lectotype male of Chaoborus eluthera (Fig. 1). [“ Chaoborus ” “eluthera” “Dyar & Snn.” “Potlatch, Ida.” “6.20, 1907” “J.M. Aldrich.” “2032” (handwritten)]. [“ USNM ENT 1240508” (printed)]. The hypopygium of the lectotype male (Fig. 1a,b) is slide mounted. Designated by Alan Stone in Belkin et al. (1966).

*note. Type material of C. alpinus was requested from various institutes and museums in Germany and Canada. It is mentioned in the original description that specimens were deposited in the collection of the author (Peus). It is likely, that Saether (1967, p. 573) studied the type specimens, because ”Professor Dr. FRITZ PEUS kindly sent me his preparations from the inundation pools of the Oder (Neumark, Bellinchen) and the Rhine (Karlsruhe), and from Lake Eibsee”, Eibsee being the type locality of the species. Besides Saether, there are no other mention of the type specimens in the literature, except Borkent (1993, 2014) stating that their location is unknown.

Other material. Finland. Ab: Naantali, Tiensuu leg. 12.VIII.1939, 1 female pinned, GV.50520 (MZH). Lohja, A. Luther leg. 23. VI.1901, 1 male pinned, GV.50509; 1 female pinned, GV.50510; 1 female pinned, GV.50511; 1 female pinned, GV.50512 (MZH). Lohja, S. Lindberg leg. 1.VIII.1927, 1 male pinned, GV.50513 (MZH). Lohja, Forsius leg. no date, 1 male, GV.50514 (MZH). Karjalohja, R. Frey leg. no date, 1 female pinned, GV.50508 (MZH). Salo, Märy, Paasivirta L. leg. 7. V.2018, 2 larva, NVO.ins2018-646 (LMM). Lohja, Kärkölä, Viitanen E. leg. 23. VIII.2017, 5 male, parameres of 2 males on slide in glue, NVO. C2020-1; 23.08.2018, 1 male, NVO.ins2018-425; 3 males, 2 females, NVO.ins2018-426; 1 male, wing, legs, head on slide, NVO.ins2018-453; 1 male, legs, head, wings, hypopygium on slide, NVO.CUL-2019-67 (LMM). N: Helsinki, Tiensuu leg. 18. VI.1949, 1 female pinned, GV.50514; 1 male pinned, GV.50515; 1 male pinned, GV.50518 (MZH). Ka: Hamina, Haukilampi, Kymijoen vesi ja ympäristö leg. 24.XI.2015, 2 larvae, NVO.ins2018-786; NVO.CUL-2019-73, 1 larva, BOLD (LMM). Hamina, Kannusjärvi, Ketola M. leg. 1.X.2014, 15 larvae, NVO.ins2018-791 (LMM). Rajala, Saima kanal, von Adelung N. leg. July 1907, 1 male pinned, GV.50519 (MZH). Ta: Iitti, Arrajärvi, Ketola M. leg. 9.X.2014, 15 larvae, NVO. ins2018-788; 1 larva, BOLD, NVO.CUL-2019-69; 1 larva, head & tail on slide, torso EtOH, NVO.CUL-2019-70 (LMM). Iitti, Märkjärvi, Ketola M. leg. 2.X.2014, 15 larvae, NVO.ins2018-790; 1 larva on slide, BOLD, NVO. CUL-2019-71; 1 larva on slide, NVO.CUL-2019-72 (LMM). Iitti, Urajärvi, Ketola M. leg. 3.X.2014, 15 larvae, NVO.ins2018-792 (LMM). Kouvola, Sompanen, Ketola M. leg. 29.IX.2014, 15 larvae, NVO.ins2018-789 (LMM). Hämeenlinna, Ilmoilanselkä, Hämeen ELY leg. 19.X.2018, 5 larvae, NVO. PM2019-01 (LMM). Sysmä, Nuoramoisjärvi, Hämeen ELY leg. 9.X.2018, 10 larvae, NVO. PM2019-02 (LMM). Loppi, Punelia, Hämeen ELY leg. 6.XI.2018, 10 larvae, NVO. PM2019-03 (LMM). Asikkala, Urajärvi, Hämeen ELY leg. 9.X.2018, 8 larvae, NVO. PM2019-04 (LMM). Urjala, Pihlajamäki, Vantanen P. leg. 18. V.2018, 4 larvae 1 pupa, NVO.ins2018-222; 1 larva, BOLD, NVO. ins2018-602; 1 larva, BOLD, NVO.ins2018-603; 1 larva, BOLD, NVO.ins2018-604; 1 larva, BOLD, NVO.ins2018- 605; 1 larva on slide, NVO.CUL-2019-74 (LMM). Urjala, Kankaantausta, Vantanen P. leg 02. VI.2018, 3 larvae, NVO.ins2018-228; 1 larva, BOLD, NVO.ins2018-606; 1 larva, BOLD, NVO.ins2018-607 (LMM). Urjala, Kankaanmäki, Härmä O. leg. 30. V.2019, 1 male e.p., pupa exuviae, legs, wings, head, hypopygium on slide; torso EtOH, NVO. CHA047 (LMM). Jokioinen, Luodesuo, Korventie, Härmä O. leg. 28. V.2019, 1 male, NVO. CHA087 (LMM); 11.IV.2020, 3 larvae, LG.6280 (FLHM). Jokioinen, Kuoppatie, Härmä O. leg. 27.III.2020, 1 male e.l., LG.6135 (FLHM). Somero, Piilammi, Härmä O. leg. 18.IV.2020, 1 larva, LG.6159 (FLHM). Tammela, Purinsuo 1, Härmä O. leg. 21.IV.2020, 1 larva, LG. 6195 (FLHM). Tammela, Saarijärvi S, Härmä O. leg. 21.IV.2020, 1 larva (FLHM). Hollola, Silmälammi, Kolcsár L.-P. leg. 01.VIII.2018, 1 male, BOLD, NVO.ins2018-63 (LMM). Orivesi, Laajaanlahti, Salmela J. leg., 15.VII.2020, 1 male e.l., larva skin and pupal exuviae on slide, NVO. LMM-el-20-129; 1 male e.l., larva skin and pupal exuviae on slide, NVO. LMM-el-20-130; 1 female e.l., larva skin and pupal exuviae on slide, NVO. LMM-el-20-134 (LMM). Orivesi, Peräjärvi, Westerling P. & Väisänen A. leg. 4. XII.2017, 1 larva, NVO.ins2018-248 (LMM). Orivesi, Horhanpuro, Westerling P. & Väisänen A. leg. 4. XII.2017, 1 larva, NVO. ins2018-249 (LMM). Pälkäne, Rautajärvi, Mattila K. leg. 22.VII.–28.VII.2018, 1 female, NVO.ins2018-455 (LMM). Tb: Jyväskylä, Tellervonkatu, Linjama T. leg. 10.VIII.–12.VIII.2018, 7 males, NVO.ins2018-209. Sa: Punkaharju, Tiensuu leg. 1950, 1 male pinned, GV.50517 (MZH). Sb: Rautalampi, Pääskylampi, Salmela J. leg. 8. V.2019, 1 larva, NVO.CUL-2019-38 (LMM). Oa: Lappajärvi, Lappajärvi, Konttinen R. leg. 13.IX.2017, 15 larvae, NVO.ins2018-247; 1 larva, NVO.ins2018-611; 1 larva, BOLD, NVO.ins2018-612; 1 larva, NVO.ins2018-613; 1 larva, NVO.ins2018-614; 1 larva, BOLD, NVO.ins2018-615 (LMM). Ok: Kuhmo, Ontojärvi, Kantola L. leg. 4.IX.1984, 4larva, NVO.chao31, NVO.chao32 (LMM). Kajaani, Nuasjärvi Kantola L.& Tikkanen P. leg. 17.IX.1984, 2 larvae, NVO.chao36 (LMM). Suomussalmi, Vuokkijärvi, Kantola L. & Tikkanen P. leg. 12.IX.1984, 7 larvae, NVO.chao87 (LMM). Suomussalmi, Vuokkijärvi, Kantola L. & Tikkanen P. leg. 13.IX.1984, 10 larvae, NVO. chao89 (LMM). Hyrynsalmi, Latvajärvi, Kolcsár L.-P. leg. 10.VIII.2018, 1 male, legs, wings, head, hypopygium on slide; torso EtOH, BOLD, NVO.ins2018-61 (LMM). Kuhmo, Roukonpuro, Kolcsár L.-P. leg. 9.VIII.2018, 4 males, 1 female, NVO.ins2018-62 (LMM). Kuhmo, Kolcsár L.-P. leg. 08.VIII.2018, 4 males, 2 females, hypopygium of one male on slide, NVO.ins2018-67 (LMM). Kuhmo, Hankaranta, Kolcsár, L-P leg. 08.VIII.2018, 1 male, mid and hind legs, head, wings, hypopygium on slide, torso in EtOH, NVO.CUL-2019-66 (LMM). Kuhmo, Roukonpuro, Kolcsár, L-P leg. 09.VIII.2018, 1 male, hind leg, head, wings, hypopygium on slide, torso EtOH, NVO.CUL-2019- 68 (LMM). Obb: Ylitornio, Selkäsaari, Salmela J. leg. 10. VI.2019, 1 female, reared, pupa exuviae in on slide, NVO. LMM-el-265. Ylitornio, Niittysaari, Salmela J. leg. 10. VI.2019, 1 male, reared, pupa exuviae mid and forelegs, wings, head, hypopygium on slide, BOLD, NVO.LMM-el-268 (LMM). Rovaniemi, Erkinlampi, Salmela J. leg. 13.VIII.2019,1 larva II instar, NVO.LMM-el-566 (LMM). Rovaniemi, Hyypiökivalo, Salmela J. leg. 13.VIII.2019, 3 larvae, NVO.LMM-el-568; 8 larva NVO.LMM-el-595; 1 larva, BOLD, NVO.CUL-2019-77; 11.IX.2019, 1 pupa, reared, NVO. CH 2020-1 (LMM). Rovaniemi, Hietaperänlampi, Salmela J. leg. 13.VIII.2019, 2 larvae, NVO.LMMel-569; 5 larvae, NVO.LMM-el-587 (LMM). Rovaniemi, Veitsikangas, Salmela J. leg. 13.VIII.2019, 1 larva, NVO. LMM-el-572 (LMM); 4 larvae, NVO.LMM-el-591; 1 larva, head & tail on slide, NVO.LMM-el-613; 1 larva, head & tail on slide, NVO.LMM-el-614; 1 larva, head & tail on slide, BOLD, NVO.LMM-el-615; 27. V.2020, 1 male e.l., larval skin and pupal exuviae on slide, NVO.LMM-el-20-84; 1 male e.l., NVO.LMM-el-20-88; 1 female e.l., NVO. LMM-el-20-103 (LMM). Rovaniemi, Koivusaari, Salmela J. leg. 7. VI.2019, 1 female, reared, NVO.LMM-el-586 (LMM). Rovaniemi, Kuusilampi, Salmela J. leg. 9. VI.2020, 1 male e.l., NVO.LMM-el-20-115; 1 male e.l., NVO. LMM-el-20-118; 1 male e.l., NVO. LMM-el-20-126 (LMM); 1 larva, 1 pupa (ABC). Rovaniemi, Varjakanlammit, Salmela J. leg. 27.VII.2019, 3 larvae, NVO.LMM-el-609; Salmela J. leg. 26. V.2020,1 male e.l., larval skin and pupal exuviae on slide, adult pinned, NVO.LMM-el-20-80; 1 male e.l., larval skin and pupal exuviae on slide, NVO. LMM-el-20-82; 1 male e.l., larval skin and pupal exuviae on slide, NVO.LMM-el-20-85; 1 female e.l., larval skin and pupal exuviae on slide, NVO.LMM-el-20-87; 1 male e.l., larval skin and pupal exuviae on slide, NVO.LMMel-20-89; 1 female e.l., larval skin and pupal exuviae on slide, NVO.LMM-el-20-90; 1 pupa e.l., NVO.LMM-el-20- 93; 1 male e.l., NVO.LMM-el-20-94; 1 female e.l., NVO.LMM-el-20-95; 1 female e.l., NVO.LMM-el-20-96; 1 male & 1 female e.p., NVO.LMM-el-20-97; 1 pupa e.l., LMM-el-20-98; 1 female e.l., NVO.LMM-el-20-100 (LMM); 2 males e.p. (ABC). Lkoc: Kittilä, Lompola, Salmela J. leg. 27.VII.2019, 1 larva, head & tail on slide, BOLD, NVO.LMM-el-603 (LMM). Lkor: Savukoski, Nimetönselkä, Laine E. leg. 10.VII.2018, 1 larva II instar, NVO. EML2018-02; 1 larva II instar, NVO. EML2018-03; 1 larva II instar, NVO. EML2018-04; 1 larva II instar, NVO. EML2018-05; 1 larva II instar, NVO.ins2019-162 (LMM). Li: Ivalo, R. Frey leg. 1911, 1 male pinned, GV.50522; 1 male pinned, GV.50525; 1 male pinned, GV.50526; 1 male pinned, GV.50527; 1 male pinned, GV.50528; 1 male pinned, GV.50529; 1 male pinned, GV.50530; 1 male pinned, GV.50531; 1 male pinned GV.50535; 1 male pinned, GV.50537; 1 male pinned, GV.50540; 1 male pinned, GV.50546; 1 male pinned GV.50547 (MZH). Inari, Iso-Söimi, Salmela J. leg., 29. VI.2020, 1 pupa, NVO.LMM-el-20-128 (LMM). Utsjoki, Geaidnogeachi, Salmela J. leg., 17.VII.2018, 3 II-III instar larvae, NVO.ins2018-485; 1 larva, BOLD, NVO.ins2018-637; 1 larva, BOLD, NVO.ins2018-638; 1 larva, BOLD, NVO.ins2018-639 (LMM).

Norway. Hordaland (Hoy), Bergen, Milde, Mildevatnet, G. Kvifte & M. Stokkan leg. 21.-24.VIII.2008, 3 males Euparal (ZMBN). Buskerud, Fla, 37, J.P. Nilssen leg., no date, 1 larva III instar on slide (CNC). Ak, Hurdal, Röystrejnet, 32 V PM 127 980; EIS 37, 190 masl, K.M. Olsen leg. 19. V.2003, 2 larvae, J.nr.32577 (KMO). AK, Nesodden, Kvistemyrdammen, 32VNM897264, 19 masl, K.M. Olsen leg. 24. V.2007, 5 larvae, 3 pupae, J.nr. KMO 40587 (KMO). Finnmark, Kautokeino, Lahpoluoppal, 69.20992N 23.757661E, 320 masl, Finnmarksprosjektet leg. 25. VI.-9.VII.2010, 1 male Euparal (ZMBN). Finnmark, Sør-Varanger, Pasvik, Russevann, 69.44497N 29.89904E, 60 masl, Finnmarksprosjektet leg. 19.-24. VI.2010, 19 males on slides (ZMBN).

Estonia. Rakujärv, Kolcsár L.-P. leg., 28.VII.2018, 1 male, BOLD, NVO.ins2018-64 (LMM).

Germany. Borken, Jugdenburg Castle, 51.83 6.85, stat.no. 30, A. Borkent leg., 20.VIII.1978, 1 larva (CNC). Brandenburg, Prignitz, Lenzen / Elbe, 53.1122 11.5383, Rulik B. leg. 13. VI.2014, 1 male, ZFMK-TIS-2526022; 1 male, ZFMK-TIS-2526023; 1 female, ZFMK-TIS-2526026; 1 female, ZFMK-TIS-2526028 (ZFMK). Mecklenburg-Vorpommern, Nationalpark Müritz, Boek, 53.42508 12.77963, Heller K. leg. 13. VI.2015, 1 female, ZFMK-TIS-2555532 (ZFMK). Hessen, Sinntal, 50.27362 9.65287, J. Kappert leg. 13. VI.2017, 1 male, ZFMK-TIS- 2601121; 1 male, ZFMK-TIS-2588956; 1 male, ZFMK-TIS-2606370 (ZFMK). Mecklenburg-Vorpommern, Insel Rügen, Kniepow, 54.35 13.35, ZFMK Malaise Trap Program leg. 26.VII.2014, 1 male, BOLD, GBOL-224104746; BOLD, GBOL-224101338; BOLD, GBOL-224101362; BOLD, GBOL-224101369; 9.6.2014, 1 male, BOLD, GBOL-224101392; 21. VI.2014, 1 female, BOLD, GBOL-224105295; BOLD, GBOL-224105462; BOLD, GBOL- 224105498 (ZFMK).

Poland. Lake near Olsztyn, A. Sikorowa leg. 14. V.1965, 2 larvae on slide, 32 (CNC). Lake Mubek near Olsztyn, A. Sikorowa leg. 20. VI.1963, 1 larva on slide (MZH).

Kazakhstan. Lake Kushmurun, Salokannel J. leg. 09.VIII.2018, 1 female, BOLD, NVO.ins2018-460 (LMM).

Russia. Petsamo, Hellen leg. no date, 1 male, GV.50523 (MZH).

Japan. Shikoku, Matsuyama, Kolcsár L.-P. leg 23.IV.2019, 1 male, BOLD, NVO. C2020-2; 1 male, NVO. C2020-3; 2 females, NVO. C2020-4 (LMM). Shikoku, Matsuyama, T. Ishihara leg. 21.IV.1952, 1 female, pinned (ELEU). Tarumi, Matsuyama, T. Ishihara leg. 2. V.1952, 5 females pinned (ELEU). Honsu, Niigata, Matsunoyama-Kannonji, Kato D. leg. 13.VIII.2020, 1 male, NVO.JAP-08; 1 male, NVO. JAP-10 (LMM).

Canada. Alberta, Siler Lake (unclear handwriting), McMillan & Smith leg. 14.VII.1970, 2 larvae III instar on slide; 1 larva II instar on slide; 1 larva IV instar on slide (CNC). Alberta, near Fort Chipewyan, 58°43ʹN 111°09ʹW, D.N. Gallup leg. June-July 1971, 1 larva on slide (CNC). Alberta, Wabumun Lake, 53°33ʹN 114°29ʹW, J. Rasmussen leg. 15. V.1972, 1 larva on slide (CNC). Ontario, Kenora, L. 120, 49.75 -93.98, G.J. Brunskill leg. 13. V.1969, emerged 22. V.1969, 1 larva, pupa exuviae, male, (same specimen) on slide, 31 (CNC). Ontario, Marmora, 44.48 -77.68, J. R. Vockeroth leg. 4. VI.1952, 1 male on slide, 40; 7. VI.1952, 1 male pinned, hypopygium in glycerol; 11. VI.1952, 7 males pinned, 1 hypopygium in glycerol; 13. VI.1952, 1 male pinned; 10.VI.1952, 1 male pinned (CNC). Ontario, Kenora, ELA 0.132.2, 49.75 -93.98, collector unknown 3.VI.1968, 1 female on slide, 0-132-2 (CNC). NWT, Mackenzie delta (NWT Pipeline Limnology Project), 68.45 -135.49, N. Snow leg. 19.IV.1972, 5 larvae, 3 in EtOH, 2 on slide, L.7-D (6) (CNC). NWT, Fort Simpson (NWT Pipeline Limnology Project), 61.85 -121.46, Crocker leg. no date, 1 larva in EtOH, RRI-11S190572DN (CNC). Ontario, N. Burgess Twp., Lanark Co., 44.80 -76.28, D.M. Wood leg. 25.VI.1967, 1 male pinned hypopygium in glycerol (CNC). Manitoba, Riding Mountain NP, 50.657 -99.974, 617 masl, BIObus leg. 12.VII.2008, 1 male, BOLD, 08BBDIP-1924 (CBG). Manitoba, Riding Mountain NP, 50.65 -99.94, 582 masl, BIObus leg. 6.VII.2008, 1 male, BOLD, 08BBDIP-2630 (CBG). British Columbia, Gulf Islands National Park Reserve, Near McDonald Campground, 48.673 -123.429, 0 masl, R. Walker & J. Mercer leg. 7.VII.2012, BOLD, BIOUG 03103- B03; 1 male, BOLD, BIOUG 03103- B06; 15.6.2012, 1 male, BOLD, BIOUG 06622- F03; 1 male, BOLD, BIOUG 06622- F05; 1 male, BOLD, BIOUG 06622- F09; 23.VII.2012, 1 male, BIOUG 06622-G02; 2.8.2012, 1 male, BOLD, BIOUG 06622- G05 (CBG). Alberta, Elk Island National Park, Astotin Lake, 53.685 -112.86, 719 masl, S. Church leg. 29. VI.2012, 1 male, BOLD, BIOUG 03291- E03; 1 male, BOLD, BIOUG 03291- F11; 1 male, BOLD, BIOUG 03291- G04; 1 female, BOLD, BIOUG 03291- G11; 1 female, BOLD, BIOUG 03291- H06; 27.VII.2012, 1 male, BOLD, BIOUG 03624- G11; 1 male, BOLD, BIOUG 03624- G12; 1 male, BOLD, BIOUG 03624- H01; 1 male, BOLD, BIOUG 03624- H03; 1 male, BOLD, BIOUG 03624- H06 (CBG). Prince Edward Island, Prince Edward Island National Park, Woodland Trail / Long Point, 46.4123 -63.085, 6 masl, P.Ayles leg. 26. VI.2013, 1 male, BIOUG 10377-H10, (CBG). Nova Scotia, New Glasgow, EQP-CLL-558, 45.567 -62.634, 33 masl, E. Stewart leg. 03.10.2014, 1 female, BOLD, BIOUG 16032- D09; 1 female, BOLD, BIOUG 16032- E06 (CBG). British Columbia, Gulf Islands National Park Reserve, North Pender Island, Roe Lake Trail, 48.781 - 123.301, 108 masl, BIObus leg. 22. VI.2014, 1 male, BOLD, BIOUG 23518- B10; 1 male, BOLD, BIOUG 23518- D01; 1 male, BOLD, BIOUG 23518- D10; 1 female, BOLD, BIOUG 23518- G06; 1 female, BOLD, BIOUG 23518- H10 (CBG). British Columbia, Victoria, 48.5197 -123.43, 63 masl, D.Faser & L. Ramsay leg. 30.VII.2014, 1 male, BOLD, BIOUG 28195- D07; 1 female, BOLD, BIOUG 28195- D12 (CBG). Ontario, Perth, Murphy`s Point Provincial Park, 44.7812 -76.2336, 143 masl, CBG Collections Staff leg. 19. VI.2014, 1 male, BOLD, BIOUG 35181- F05; 1 male, BOLD, BIOUG 35181- F12; 1 male, BOLD, BIOUG 35181- H01; 1 male, BOLD, BIOUG 35181- H04; 1 male, BOLD, BIOUG 35187- A06; 1 male, BOLD, BIOUG 35187- A07; 1 male, BOLD, BIOUG 35187- A11; 1 male, BIOUG 35187-B03; 1 male, BOLD, BIOUG 35187- B11; 1 male, BOLD, BIOUG 35187- B12; 1 male, BOLD, BIOUG 35187- D04; 1 male, BOLD, BIOUG 35187- D06; 1 male, BOLD, BIOUG 35187- D10; 1 female, BOLD, BIOUG 35187- F07 (CBG).

USA. Arizona, Walker L., Green J. leg. 29.VII.1982, 1 larva on slide (CNC).

Redescription. Adult male. Head light brown, bearing pale setae. Non–setose area of occiput whitish, frontal macula bare. Antennal flagellomeres pale. Length of penultimate flagellomere 281 (262–296, n=11), apical flagellomere 239 (214–257, n=9), penultimate/apical 1.18 (1.04–1.36, n=9). Lengths of palpal segments 2–5 (n=10 except 5th palpal segment n=8): 111 (101–129), 218 (201–248), 196 (174–222), 370 (331–409). Thorax. Scutum with orange–dark brown scutellar stripes; ground color straw yellow–light grayish, setae pale (Fig. 3a,b). Scutellum and mediotergite orange–dark brown. Coloration of pleuron composed of pale and dark areas: ventral part of katepisternum about as dark as scutellar stripes; antepronotal lobe, postpronotum, anepimeron, part of metanepisternum and part of anepisternum slightly darkened, halteres whitish (Fig. 4). Thoracic setae (n=5, except katepisternal and postpronotal n=4): antepronotal lobe 32 (25–36), postpronotal 5 (4–5), proepisternal 8 (7–8), katepisternal 4 (3–4), anepisternal 11 (8–15), anepimeron 8 (4–10), supra–alar 2 (2–3). Legs pale–straw yellow, apical tarsomeres slightly darkened. Foreleg, lengths of fe, ti and ta1–ta5 (n=10): fe 1737 (1517–1922), ti 1865 (1559–2097), t1 787 (650– 901), t2 496 (420–557), t3 398 (332–455), t4 264 (210–307), t5 193 (169–219). Midleg, lengths of fe, ti and ta1–ta5 (n=10): fe 1606 (1445–1802), ti 1558 (1353–1902), t1 665 (557–815), t2 426 (358–547), t3 342 (301–429), t4 220 (197–281), t5 181 (155–197). Hind leg, lengths of fe, ti and ta1–ta5 (n=8): fe 2002 (1875–2198), ti 1903 (1722– 2107), t1 1102 (989–1199), t2 621 (563–698), t3 442 (408–481), t4 246 (229–271), t5 192 (169–205). Wing (n=10). Length 3862 (3394–4170), width 884 (771–952), length/width 4.38 (3.71–4.57); fork of R 2+3 423 (330–490), fork of M 1+2 402 (322–476), R 3 1302 (1149–1539), M 1 1113 (988–1226), number of setae on squama 35 (30–42, n=9). Abdomen. Ground color of tergites pale yellowish or grayish, first tergite brownish, brown basal band of second tergite very wide, with a median lobe, third–fifth tergites with a subapical brown band, median lobe modest; bases of setae with a dark ring (Fig. 5a). Hypopygium (Fig. 6). Gonocoxite most often yellowish brown, rarely dark brown, length 534 (477–655), width 169 (141–199), length/width 3.05 (2,37–3,46), n=9); gonostylus brown–dark brown, rather narrow, length 428 (364–462), width 31 (27–36), length/width 13.74 (11.86–16, n=10); paramere usually bicolorous, basal part pale, apical claw infuscated, in some specimens dark all over; medially bent and constricted; apical claw rather narrow, slightly curved (viewed from above) (Fig. 6 b–e, 8a); subapical crest present or absent; if present may vary in width (Fig. 7); length 141 (118–160, n=9).

Adult female. In general similar to male, with usual sexual differences. Penultimate flagellomere (152–180, n=2), apical flagellomere (195–206, n=2), penultimate/apical 0.78–0.87. Lengths of palpal segments 2–5 (n=3 except 5th palpal segment n=1): 117 (109–129), 224 (207–236), 208 (188–219), 401. Thoracic setae (n=2): antepronotal lobe 31–37, postpronotal 7, proepisternal 7–9, katepisternal 7–8, anepisternal 18–19, anepimeron 15–17, supra–alar 2. Wing length 4503 (4263–4701), width 1216 (1167–1303), length/width 3.71 (3.49–3.99); fork of R 2+3 391 (348–467), fork of M 1+2 396 (326–450), R 3 1698 (1682–1723), M 1 1512 (1478–1558), number of setae on squama 43 (26–53) (n=3). Foreleg, lengths of fe, ti and ta1–ta5 (n=1–2): fe 1845–1893, ti 1898–1993, t1 930, t2 556, t3 441, t4 292, t5 212. Midleg, lengths of fe, ti and ta1–ta5 (n=3): fe 1671 (1576–1753), ti 1573 (1458–1694), t1 713 (665–712), t2 426 (409–446), t3 298 (251–323), t4 236 (222–250), t5 195 (183–199). Hind leg, lengths of fe, ti and ta1–ta5 (n=3): fe 2085 (1887–2298), ti 2082 (1903–2200), t1 1196 (1140–1239), t2 664 (635–700), t3 459 (443–485), t4 271 (244–301), t5 215 (203–231). Abdominal tergites (Fig. 5b) 3–5 with relatively wide subapical bands, median lobes wider than in males.

Pupa. Thoracic respiratory organ constricted subapically, either slender (pond populations, Fig. 9a, length 1034 (920–1181), width 250 (207–282), length/width 4.16 (3.8–4.47, n=8)) or voluminous (lake populations, Fig. 9b, length 1108 (1011–1364), width 401 (386–413), length/width 2.75 (2.47–3.3), n=4). Lateral ribs of terminal processes brown to light brown, mid rib brown to dark brown; in lake-dwelling specimens all ribs may be pale.

IV instar larva. Mandibular fan bristles 13 (11–15, n=24). Apices of mandibular teeth 1, 2 and 4 darkened, otherwise pale, especially in lake-dwelling populations; in pond populations tips may be more extensively darkened, including tooth 3 (Fig. 10a,b). Average number of lateral teeth 4.3 (3–6, n=23), uppermost tooth smaller than mandibular tooth 3 (Fig. 9a,b). Labral blade (Fig. 10c) almost always serrated, length 276 (245–327), width 59 (48–68), length/width 4.72 (3.77–5.95, n=25). Length of antenna 543 (477–670, n=24). Number of anal fan setae 23 (20–26, n=23). Anal hook pale–brown in color.

DNA barcoding. Chaoborus flavicans was the most genetically divergent member of the complex, being over 30 % divergent from the most closely related congener (Table 1). The average pairwise tree distance of sequences (intra) for this species was modest at 2.4 %. However, this average was inflated by the presence of differentiated geographic clades (Nearctic and Palearctic; Fig. 15). The most basal sequence of C. flavicans was from Japan where the divergence was 7 % from Holarctic C. flavicans. These geographic clades presumably resulted from survival in separate Pleistocene glacial refugia (although the more divergent Japanese lineage may predate the Pleistocene). There was regional variation within the Palaearctic (Fig. 15). The barcoded Japanese specimen forms a unique BIN in BOLD (BOLD:AEF3847), that is 4.28 % (K2P) distant from the nearest Palaearctic C. flavicans specimen. Palaearctic haplotype subgroups formed two BIN clusters in BOLD, BOLD:ACB8413 and BOLD:ADT7895. The members of the former were mainly from ponds and small lakes, collected from Finland, Estonia, Norway, Germany, Kazakhstan and China, while the latter was composed of Finnish and South Korean specimens mostly from large, thermally stratified lakes. Nearctic specimens clustered in a single BIN (BOLD:AAG5462). The probability of identification of C. flavicans from barcoding information alone was high (97%).

Comments. Adults of C. flavicans are typically relatively light in their coloration. Scutellar stripes and adjoining integument are orange-brown or light brown, ground coloration is pale yellow or straw yellow, and pleural sclerites follow the same pattern. Abdominal tergites are yellowish brown with darker subapical bands on tergites 2–5. Based on these color patterns, adult specimens can be identified to species with high confidence. However, some specimens are darker, and for example, thoracic markings approach black in color (Fig. 4) and abdominal tergites are more uniformly darker. Parameres of adult males are medially bent and constricted, with the apical claw dark and relatively narrow. Pupae of C. flavicans are hard to separate from those of C. albipes, especially among pond populations that have slender respiratory organs. Larvae of C. flavicans are unique in the possession of small lateral mandibular teeth. Additional measurements from larvae and pupae are available e.g. from Parma (1969), Saether (1967) and Sikorowa (1973).

Saether (1967) was the first to study the variation of C. flavicans in a Holarctic context. His study was mainly based on larvae and pupae, but the parameres of adult males were also examined. First of all, Saether synonymised C. alpinus with C. flavicans but he named three forms, flavicans, alpinus and infuscatus. These forms should display differences especially in larval coloration, shape of pupal respiratory organ, and shape and coloration of male paramere (as “genital sclerite”). However, as Saether himself discusses, these characters are mostly overlapping and at least partly influenced by the environment. It should also be noted that the material studied by Saether was treated in KOH, which may obscure coloration patterns (Borkent 1979). Saether did not explicitly assign the studied specimens to these forms, but it may be deduced that f. flavicans and f. alpinus are European and f. infuscatus is North American.

Above all, it may be assumed that all specimens studied by Saether (1967) actually belong to C. flavicans, not to the two other species covered in the present revision. This is due to the shape of parameres depicted by him and the fact that specimens were mostly collected from larger lakes, not from ponds. Thus, Saether’s study provides a good source to assess intraspecific variation of C. flavicans, especially for measurements of specific structures and numbers of setae.Among the characters, the pupal respiratory organ and male paramere are particularly discussed as follows because these are otherwise important in Chaoborus taxonomy (e.g. Martini 1929; Peus 1934; Berg 1937; Saether 1970; Borkent 1979).

The forms that Saether (1967) described differ in some regards. The respiratory organ is present either as a slender (f. flavicans) or a broad form (f. alpinus, infuscatus) (Fig. 9a,b), and its function is to keep the pupa in upright position in the water (A. Borkent pers.comm.) and provide stability during emergence (Parma 1971a). The f. infuscatus may have strong spicules on the whole surface and in f. alpinus these spicules are apparently lacking. Broad or voluminous respiratory organs are present in lake populations. In contrast, slender organs are present in pond populations, such as among the pupae described by Peus (1934) from the inundation pools along large rivers in Germany (see also Saether 1967, table 2). Organ volume may be affected by environmental conditions such as wave action (i.e., phenotypic plasticity). In smaller lentic waters, slender organs may suffice for safe emergence. On the other hand, organ width may be a genetically fixed trait. Finally, presence or absence of spicules in the two forms may be at least partly artefactual in nature. If one looks at the surface of the organs with high magnification, it can be seen that such spicules are indeed present on slender organs; instead of protruding, the spicules are appressed to the lamina.

The subapical crest of the male paramere may be present (f. alpinus) or absent (f. flavicans, infuscatus); if present, it may vary in size (Peus 1938; Saether 1967). Among the material studied in this revision, the presence of a crest is the prevailing character, and we agree that its size may vary (Fig. 7). However, unlike in Saether (1967), the crest was also present in Nearctic specimens. One male from northern Norway (Kautokeino) possessed the paramere of the f. infuscatus (dark, crest absent) type. Chaoborus flavicans parameres figured by Cook (1956) actually depict C. albipes, and thus Saether’s comment, in reference to Cook (1956), “without having a wing-like crest” for Nearctic specimens is not valid. It should also be noted that the paramere is a complex structure, and its position on the slide or angle to the viewer may influence whether the crest is visible or not. We thus conclude that the formae and their traits presented by Saether are geographically vastly overlapping and bear only limited or minimal taxonomic importance.

Sikorowa (1973), among other things, studied the larval instars and intraspecific variation of C. flavicans in Poland. According to her results, pond and lake populations differ in some larval characters. For example, larvae from lakes are more transparent than those from ponds, which is at least partly explained by the algal growth in the cuticula of pond-dwelling specimens (Sikorowa 1973, p. 15). Moreover, pond larvae are larger than lake larvae (Sikorowa 1973, table 3). However, Sikorowa also examined the presence/absence of the subapical crest of male parameres between pond and lake populations. This data is not quantified, but she states that the subapical crest may be present in both populations, and despite differences in larval characters, this variation should be considered as intraspecific.

Distribution. The species has a broad Holarctic range. It is widely distributed in the Nearctic Region, despite hitherto confusion with C. albipes (e.g. in Cook 1956; Borkent 1981). In the Palaearctic it occurs from Ireland to Japan and from northern Fennoscandia and western Russia to Italy, Sardinia and Spain (this study, Aitken 1954; Wende et al. 2006; Arranz et al. 2015; Andersen & Kvifte 2012).

Ecology. Mostly univoltine in the boreal–north temperate region, rarely bivoltine (Berg 1937; Hirvenoja 1960; Regmi et al. 2013), but may produce three generations in fishless ponds in Poland (Sikorowa 1973). Records of 5–6 annual generations in Japan (Xie et al. 1998) may also concern C. albipes or Chaoborus sp. (see below). Very common in dystrophic, eutrophic, or turbid lakes and may attain high densities, up to tens of thousands per square metre in bottom samples (Stahl 1966a; 1966b; Parma 1971a; Liljendahl-Nurminen et al. 2002). Fourth instar larvae perform diel vertical migrations, i.e., being present in the sediment or hypolimnion during day and epilimnion during night (Valle 1930; Berg 1937; Parma 1971a; Sikorowa 1973). Larvae penetrate the sediment (Gosselin & Hare 2003) and may also feed there (Parma 1971a). Most of the feeding occurs at night in the epilimnion where larvae prey upon planktic crustaceans (Sikorowa 1973; Jäger et al. 2011). In ponds of riverine flood-plains, larvae can be present in shallow water close to shore and devour young Ochlerotatus mosquito larvae (JS pers.obs.). Larvae respond to the presence of fish via chemical cues (Dawidowicz et al. 1990) and are photophobic (orient to darkness) (Parma 1971a). Fourth instar larvae overwinter and pupation in lake populations occurs typically in mid or late summer (Berg 1937). Pupae also perform vertical migrations (Parma 1971a). Adults emerge on the surface at night and live about 1–4 days (Parma 1971 a, Sikorowa 1973). Males may form large swarms in the lake shores around sunset (Berg 1937). Females lay eggs in roundish, floating egg masses and a female may lay only one batch of eggs (ca. 300 eggs, Sikorowa 1973). Ovipositing females do not discriminate between lentic habitats with or without fish (Berendonk 1999). First instar larvae hatch from the eggs within a few days and remain mainly in the surface waters during the first three instars (Parma 1971a; Sikorowa 1973). Fourth instar larvae finally aggregate to the deepest parts of the lake and may be present in lake bottoms of several tens of meters deep (Bardenfleth & Ege 1916). From late autumn to spring larvae hibernate in bottom sediments (Kajak & Rybak 1979). Larvae can also be present in fishless ponds (Sikorowa 1973; Garcia & Mittelbach 2008), but at least in some regions, these ponds are close to larger water bodies (JS pers.obs., Borkent 1981). Larvae of pond populations are usually somewhat larger and darker than those in lakes (Sikorowa 1973; JS pers.obs.). The species is also reported to occur in temporary ponds (Peus 1934; Kuper & Verberk 2011; Arranz et al. 2015), but these are results of the spill-over of larvae from adjacent water bodies (Borkent 1979) and ovipositing females from permanent populations (Berendonk & Bonsall 2002). Pond populations of C. flavicans emerge in late May or early June in Finland, and in late April in Poland (Sikorowa 1973). In Finland, C. flavicans is generally very rare or absent from chaoborid communities of fishless ponds. There is evidence that the larger and dominant species C. obscuripes (Palaearctic) may displace C. flavicans from fishless water bodies (Wissel & Benndorf 1998). However, C. flavicans and C. obscuripes may coexist if the water body is deep enough to permit spatial segregation of the two species (Hongve 1975).