Egle atomaria ( Zetterstedt, 1845 )

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 : 33-35

8. Egle atomaria ( Zetterstedt, 1845)

Figs. 91–96 , 176, 177 .

Aricia atomaria Zetterstedt, 1845: 1624 . Hylemyia (Chortophila) salicola Huckett, 1928: 79 , figs. 1–3. Synonymized by Ackland (1970: 190). Hylemyia (Egle) atomaria (Zetterstedt) ; Ringdahl 1933: 29 (in part); Ringdahl 1939a: 45; Ringdahl 1939b: 146. Egle atomaria (Zetterstedt) ; Ringdahl 1951: 153 (in part); Ringdahl 1952: 176; Ringdahl 1959: 272 (in part); Lyneborg

1965: 224, figs. 23–25; Hennig 1967a: 138, plate-figs. 141, 142, 150; Ackland 1970: 188, 190, figs. 13, 14; Hennig

1976: 937, 938; Michelsen 1985: 41; Dely-Draskovits 1993: 51; Griffiths 2003: 2365, figs. 2689–2693; Michelsen

2004. For further references, see Griffiths (2003).

Taxonomic note. Ringdahl (1933) and subsequent authors correctly assigned Zetterstedt’s name atomaria to Egle , but with an ambiguous species concept embracing various very small species of Egle without setal tufts on the male sternite V. Collin (1947) sunk E. atomaria as a junior synonym of E. minuta (Meigen) , but this was shown to be a mistake by Lyneborg (1965) who settled the present identity of Zetterstedt’s Aricia atomaria by designation of a lectotype.

Description. Extremely small: wing length 2.3–3.0mm.

Male. Palp distinctly expanded on distal part. Parafacial in middle narrow, about half as wide as postpedicel. Lower facial margin reaching distinctly beyond weakly developed fronto-parafacial angle. Genal setae in two irregular rows. Apparently 2 prealar setae, both short and stubby, at most half as long as posterior notopleural seta. Even setulae on anterior part of mesonotum and on postpronotal lobes short and stubby. Proepisternals 1(–2); proepimerals 1–2. Scutellum without usual minute setulae beneath tip. Lower calypter very short, hind margin nearly straight. Submedian tibial setae: fore tibia with 1–2 long and hair-like pd-setae, without p–pv-setae; mid tibia with 0 ad-, 2 pd- and 0 p-setae; hind tibia with 0 av- and 0 p–pv-setae. Hind femur with short pv-setae on basal two-thirds. Tergite VI separate from syntergosternite VII+VIII. Sternite V ( Figs. 91, 92 ) with short, tapering posterior lobes; basal plate with several rather short setae disti-laterally; similar setae present latero-basally and at hind margin of posterior lobes. Terminalia ( Figs. 93–96 ): shape of surstyli and cerci diagnostic.

Female. Haustellum notably thick; prementum mat, extensively covered in thin dusting. Palp distinctly expanded on distal part, narrowly spoon-shaped. Lower facial margin weakly produced but reaching distinctly beyond weakly developed fronto-parafacial angle. Apparently 2 prealar setae, both short and stubby, at most half as long as posterior notopleural seta. Even anterior margin of mesonotum and postpronotal lobes with short and stubby setulae. Proepisternals 1; proepimerals (1–)2. Scutellum bare beneath tip, without usual minute setulae. Lower calypter very short, nearly straight at hind margin. Submedian tibial setae very few: fore tibia with 1 hair-like pd- and 0 p–pv-setae; mid tibia without ad-, 1 pd- and 0 p-setae; hind tibia with 0 avsetae. Oviscapt ( Fig. 176, 177 ): Sternites VI and VII extensively membranised on posterior two-thirds, at the most a little sclerotized near hind margin sternite VI; sternite VIII very reduced but with pair of setulae still discernible; small epiproct with a pair of short setulae; hypoproct V-shaped, with ca. 4 marginal setulae; cerci small, moderately slender. Spermathecae two normal-sized, cross-wrinkled, third spermatheca absent, represented by rudimentary duct only.

Material examined. FINLAND [ FMNH, ZMUC]: Ostrobottnia australis: Alavus , 11 males 14.v.1940 (L. Tiensuu). Ostrobottnia borealis (N): Rovaniemi, Pisa, 1 male 15.vi.1951 (H. Lindberg). Lapponia kemensis (W): Muonio, 1 male (W.E. Hellén); Pallastunturi, 3 males (W.E. Hellén). Lapponia enontekiensis: Kilpisjärvi, 1 male (W.E. Hellén) ; NORWAY [ ZMUC]: Sør-Trøndelag (inner): Kongsvoll , 900–1100m, 29 males, 11 females 12–20.vi.1985 ( V. Michelsen) . SWEDEN [ MZUL, ZMUC]: Jämtland: Åre , 2 males, 5 females 7–11.vi.1948 (H.C. Huckett): Torne Lappmark: Abisko, 1 female 18.vi.1951, 1 male, 2 females 20.vi.1951 (J. R. Vockeroth), 1 female 28.v.1973, 1 female 22.vi.1973 (B.G. Svensson). Nearctic specimens seen from : USA [ ZMUC]: New York: Riverhead, Long Island , 1 male, 3 females 15.iv–2.v.1926 –27 (H.C. Huckett) .

Biology. Adults are usually collected on flowering willow shrubs. Larval development surely takes place in the female catkins of various Salix spp.

Distribution. A Holarctic species, but Palaearctic records are so far confined to subarctic localities in northern and elevated parts of Fennoscandia: Finland ( Michelsen 2004), Norway ( Ackland 1970) and Sweden ( Lyneborg 1965). The inclusion of the species in a checklist from Poland ( Draber-Moṅko 1991) is certainly based on a misidentification. Widely distributed in subarctic and boreal northern North America ( Griffiths 2003), where the species extends as far south as Long Island (New York) on the east coast.

Relationships. As stated by Griffiths (2003), E. atomaria takes up an isolated position within the Egle minuta section.

Figures

FIGURES 91–96. Egle atomaria, male terminalia. 91, 92. Sternite V, ventral and lateral views. 93, 94. Hypopygium, caudal and lateral views. 95. Pre- and postgonites, lateral view. 96. Phallus, lateral view. Same scale.

FIGURES 176–179. Egle spp., female terminalia. 176. E. atomaria, oviscapt, flat mounted. 177. Same, spermathecae. 178. E. parvaeformis, oviscapt, flat mounted. 179. Same, spermathecae. Different scales.