Spilogona hennigi, Sorokina, 2025

Sorokina, Vera S., 2025, New taxonomic notes on the genus Spilogona Schnabl, 1911 (Diptera: Muscidae) in Arctic Russia, with the description of three new species, Zootaxa 5584 (1), pp. 1-25 : 5-7

Spilogona hennigi sp. nov.

Figs 1 A–E

Limnaricia pauxilla ( Holmgren, 1869) ; Frey, 1915: 28 (West Taymyr, New-Siberian Islands). Misidentification.

Spilogona hirticauda ( Malloch, 1921) ; Hennig, 1959b: 302 (West Taymyr, New-Siberian Islands). Misidentification.

Notes. Over the past 100 years, questions have been raised around three species: Spilogona hirticauda ( Malloch, 1921) , Spilogona obsoleta (Malloch, 1920) , and Spilogona novaesibiriae ( Frey, 1915) . Malloch (1921) described Melanochelia hirticauda from St. Paul Island, Alaska. Later, Huckett (1932) compared paratypes of Melanochelia hirticauda with the male holotype of Limnophora obsoleta and considered them identical species. However, Hennig (1959b) resurrected Spilogona hirticauda (Malloch) as a possibly valid species occurring in Alaska and the Far East of Russia, but this was not followed by Huckett (1965) and Pont (1986). Hennig’s doubts were caused by Frey’s paper (1915), where an unknown species was described and illustrated with the genitalia under the name “ Limnaricia pauxilla ( Holmgren, 1869) ” ( Fig. 1C, D ). Collin (1930) illustrated a similar form of surstylus in an Alaskan specimen (Savonoki, Naknek Lake) under the name “ Limnophora obsoleta Malloch ”, and synonymized Spilogona pauxilla (Holmgren) with Spilogona megastoma (Boheman, 1866) . Hennig studied Frey’s specimens from West Taymyr and the New-Siberian Islands, as well as Collin’s drawings of the Alaskan specimen ( Collin, 1930: Plate XIX, 16b1), and concluded that these specimens belong to Spilogona hirticauda . Hennig indicated that these specimens are very close to Spilogona novaesibiriae and Spilogona obsoleta but differ significantly from both in the male genitalia ( Fig. 1E ).

Relatively recently, Sorokina and Michelsen (2014) supported the view that Spilogona hirticauda (Malloch) is a synonym of Spilogona obsoleta and Spilogona novaesibiriae . This opinion, like the opinion of probably many other researchers, was based on the fact that Frey’s illustrations (1915: Taf. II, Figs 23–24) and Hennig’s illustrations (1959a: Taf. XV, Fig. 312) show Spilogona obsoleta from different perspectives.

However, I recently received muscid material for identification from Franz Josef Land. The specimens are very similar to Spilogona novaesibiriae . I examined the male genitalia and they are absolutely identical with Frey’s illustrations (1915: Taf. II, Figs 23-24) and Hennig’s illustrations (1959a: Taf. XV, Fig. 312), and they are completely different from the genitalia of Spilogona obsoleta from the same perspective. My first thought was that Hennig was right and Spilogona hirticauda is a valid species. Unfortunately, the type specimens of Spilogona hirticauda were not dissected and it is not possible at this time to study the type to confirm this statement. Huckett (1932) studied a paratype and noted that the description of Melanochelia hirticauda is entirely consistent with Spilogona obsoleta .

After studying Malloch’s description of Melanochelia hirticauda (1921), I found several distinctive differences from the specimens from Franz Josef Land and, therefore, from Hennig’s description. In addition to the structure of the male genitalia, these differences include the width of frons, the face in profile, the chaetotaxy of legs, and colour of female scutum. In addition, the locality of Melanochelia hirticauda is significantly further south than the locality of specimens from Franz Josef Land and of Frey’s specimens from the New Siberian Islands. I have thus concluded that the species discussed by Hennig is not Spilogona hirticauda but is a species new to science.

The new species appears therefore to be an exclusively arctic species that also inhabits the high Arctic of the Nearctic region, and so it may be found among series of Spilogona obsoleta in museum collections. As regards of the Alaskan specimen (Savonoski, Naknek Lake) described by Collin (1930: 272, Plate XIX, 16b 1), the surstylus is similar to the new species in its bend, but the shape is different: the surstylus does not protrude much above the epandrium; the cerci are also wide, as in Spilogona obsoleta . In view of these characters and the more southern locality of the Alaskan specimen, it is most unlikely that it belongs to the new species.

Type material: Holotype ♂, RUSSIA, Franz Josef-Land : Hooker Island, stream , 37 m, 80°20’N 52°48’E, 10.viii.2016, leg. A. Krasheninnikov ( SZMN) . Paratypes: RUSSIA, Franz Josef Land: 1♂ 2♀♀, Hayes Island , Cape Observatorskii, tundra, 3.viii.2012, leg. I. Mizin ; 1♀, Kane Island , Cape Gagara (Loon), coastal tundra, 81°05’N 58°30’E, 9.viii.2013, leg. M. Gavrilo ; 3♀♀, Hooker Island , Tikhaya Bay, tundra, 80°20’N 52°48’E, 4, 5, 17.viii.2014, leg. M. Gavrilo ; 2♀♀, Hooker Island , stream, 80°20’N 52°48’E, 10.viii.2016, leg. A. Krasheninnikov ; 1♀, Hooker Island , Tikhaya Bay, polar station, 80°20’N 52°46’E, 41 m, 10.viii.2016, leg. A. Krasheninnikov ; 7♀♀, Aldzhera Island , stream, 80°22’N 55°50’E, 13 m, 17.viii.2016, leg. A. Krasheninnikov (all in SZMN).

Etymology. The species name is a patronym in honour of the famous dipterologist W. Hennig, who was the first to describe and illustrate it.

Diagnosis. The new species is very similar to Spilogona novaesibiriae ( Frey, 1915) and can be separated from it as follows:

- Mid femur with 5–9 strong pv setae in basal half which are as long as diameter of femur or a little longer, without av setae; hind femur with short strong pv setae which are usually shorter than diameter of femur or sometimes a little longer; scutellum with downwardly-directed preapical setulae on upper border of declivities. Male: frontal vitta wide, distance between eye margins on upper part of frons as wide as frontal triangle or greater; surstylus semi-oval in shape, rounded at apex, without a platform with setae projecting above epandrium; cerci in lateral view broader, with convex inner margin. Female: scutum light, with three brown longitudinal stripes and sometimes with light brown dust between them.................... S. novaesibiriae

- Mid femur with a numerous long hair-like pv setae which are longer than diameter of femur and often with short hair-like setae on av-v surfaces; hind femur with elongate hair-like pv setae in basal half; scutellum without downwardly-directed preapical setulae on upper border of declivities. Male: frontal vitta narrower, distance between eye margins on upper part of frons narrower than frontal triangle; surstylus triangular in shape, pointed at apex, with a platform with setae projecting above epandrium; cerci in lateral view narrow, more or less straight. Female: scutum darker, with four black longitudinal stripes and brown dust between them................................................................. S. hennigi sp. nov.

Description. Hennig gave a good description of this species under the name “ Spilogona hirticauda ” and pointed out its great similarity to Spilogona novaesibiriae ( Hennig, 1959b: 302) . All the differences found between these two species are indicated in the diagnosis above.

As further differences, Hennig in his key (1959a: 260) also described a white wing and a completely yellow haltere for Spilogona novaesibiriae but a yellowish wing and a brown-black haltere for “ Spilogona hirticauda ”. However, these characters are variable as the series of Spilogona novaesibiriae as well as in the series of Spilogona hennigi sp. nov.

Comment. Because the type series has been extracted and pinned from alcohol, the flies are not in very good condition, which makes description difficult.

Distribution. PALAEARCTIC: Russia (Arctic Siberia: Franz Josef Land, West Taymyr, New-Siberian Islands).?NEARCTIC.

Figures

FIGURE 1. Spilogona hennigi sp. nov. A. Terminalia, lateral view (paratype). B. Cercal plate, dorsal view (paratype). C. Terminalia, lateral view (from Frey, 1915). D. Cercal plate, dorsal view (from Frey, 1915). E. Terminalia, lateral view (from Hennig, 1959a).