Egle pilitibia ( Ringdahl, 1918 )

Michelsen, Verner, 2009, Revision of the willow catkin flies, genus Egle Robineau-Desvoidy (Diptera: Anthomyiidae), in Europe and neighbouring areas, Zootaxa 2043 (1), pp. 1-76 : 30-32

7. Egle pilitibia ( Ringdahl, 1918)

Figs. 82–90 .

Chortophila pilitibia Ringdahl, 1918: 193 . Hylemyia (Egle) pilitibia (Ringdahl) ; Ringdahl 1931: 19; Ringdahl 1933: 29; Ringdahl 1939a: 45. Hylemyia pilitibia (Ringdahl) ; Séguy 1937: 107. Egle pilitibia (Ringdahl) ; Ringdahl 1951: 153, 176; Ringdahl 1952: 178; Ringdahl 1959: 271, figs. 35, 129; Hennig

1967b: 146, plate fig. 140; Ackland 1970: 187, 192; Hennig 1976: 937; Ólafsson 1991: 55; Dely-Draskovits 1993:

52; Griffiths 2003: 2312, figs. 2609–2616; Michelsen 2004. For further references, see Griffiths (2003).

Description. Medium-sized, wing length 3.5–4.7mm. Resembling Egle brevicornis , but easily identified by notopleuron without accessory setulae and hind tibia without apical pd-seta. Other notable differences: Prementum mainly shining, only with traces of dusting on distal part. Dorsocentral rows with 3–4 pairs of setae behind suture. Fore tibia with 1–3 longish hair-like pd-setae in addition to some p-setae. Mid tibia with 2–4 pd-setae. Hind tibia with 4–7 short av-setae. Male differences: Katepisternals 1 + 1(–2). Hind tibia with some p–pv-setae on middle third. Terminalia ( Figs. 82–87 ): Sternite V enlarged with exposed and shiny subbasal swelling. Shape and setation of sternite V, cerci and gonites different from other West Palaearctic species. Egle rectapica described from China has very similar terminalia (see under Relationships). Female differences: Katepisternals (0–)1 + 1. Hind femur without row of longish pv-setae. Oviscapt ( Fig. 88–90 ): As in the Egle brevicornis species group except sternites VI and VII considerably broader. One of the three spermathecae moderately reduced in size according to my observations, but this may be a variable condition, as Griffiths (2003) described the three spermathecae as of equal size.

Geographic variation. Examination of the terminalia of a male from Canada revealed some differences from European males as follows: Sternite V without prominent transverse hump on distal part of basal plate; posterior lobes with fewer lateral setae, apically more slender in lateral view and with fewer setulae; pregonite more declining on distal part. If these differences prove stable throughout the North American range, it may seem warranted to assign the Nearctic populations to a separate species.

Material examined. ICELAND [ ZMUC]: Thjorsarver , 1 male 14.vi.1973, 1 female 17.vi.1973 (E. Ólafsson) . NORWAY [ ZMUC]: Hordaland (inner): Rjoto, Eidfjord, 990m, 1 female 21.vii.1967 ( T. Nielsen et al.); Finse, Ulvik , 1220–1350m, 1 male 17.vi.1981 (K. Rognes) . RUSSIA [ ZMUC]: Murmansk Oblast: Kola , 1 female (J.A. Palmén) . SWEDEN [ MZUL; ZMUC]: Jämtland: Undersåker , 1 female 26.vi.1925 (O. Ringdahl); Vällista, 1 male 22.vi.1925, 1 male 21.vi.1939 (O. Ringdahl); Torne Lappmark: Abisko, Toppstugan, 900m, 1 female 3.vi.1973 (B.G. Svensson). Nearctic specimens seen from : CANADA [ ZMUC]: British Columbia: Summit Lake, Alaska Hwy , 5000ft., 1 male 25.vi.1959 (E.E. MacDougall) . Manitoba: Churchill, 1 male 25.vi.1948 (G.E. Shewell); Fort Churchill , 1 female 3.vi.1952 (J.G. Chillcott) .

Biology. A subarctic to arctic species often found above the treeline in association with flowering Salix shrubs. In Canada (Northwest Territories) it has been bred from larvae in female catkins of Salix glauca L. and S. arctophila Cockerell ( Griffiths 2003) .

Distribution. A Holarctic species, but Palaearctic distribution poorly known: Finland and adjacent northern Russia ( Michelsen 2004), Iceland ( Ólafsson 1991), Norway ( Michelsen 2004), Sweden ( Ringdahl 1952). Recently collected by A. Grossmann (in litt.) in Austria. Nearctic distribution summarized by Griffiths (2003) as USA: Alaska; Canada: Alberta, British Columbia, Manitoba, Northwest Territories, Quebec and Yukon.

Relationships. As judged from illustrations of the male terminalia ( Jin et al. 1981: 92, figs. 7–9), the Chinese Egle rectapica Ge & Fan is overall very similar, but different in some details of the male cerci and surstyli.

Figures

FIGURES 82–87. Egle pilitibia, male terminalia. 82, 83. Sternite V, ventral and lateral views. 84, 85. Hypopygium, caudal and lateral views. 86. Pre- and postgonites, lateral view. 87. Phallus, lateral view. Same scale.

FIGURES 88–90. Egle pilitibia, female terminalia. 88. Oviscapt, flat mounted. 89. Distal oviscapt, lateral view. 90. Spermathecae. Same scale.