Myolepta angustifacia, Steenis, 2020

Steenis, Jeroen Van, 2020, A new species of the genus Myolepta Newman (Diptera: Syrphidae), with short description and key to all species of the M. vara subgroup, Zootaxa 4750 (3), pp. 370-390 : 372-375

Myolepta angustifacia sp. n.

Figs 1 A−B, 3A–C, 4A−B, 7A−B, 8A−B, 10A, 11A, 13A, 17A−B urn:lsid:zoobank.org:act:FC404DED-2657-4364-AEF4-1E37396D9664

As Myolepta vara in: Mutin & Barkalov 1999: 460; Sivova et al. 1999: 2

Type material. HOLOTYPE ♂, Russia: “ Russia, Siberian Far East / Khabarovski Kray, Amur river / Komsomolsk nature reserve / 50°42’55”N 137°21’40”E / 10-06-2013, 25 m a.s.l. / J van Steenis Sib13-59”, “ Myolepta sub-group / fig no JvSMo1-001” ( NBC) . PARATYPES 13♂, 10♀. Russia: “Комсомолск н/А / сквер КГПИ / 8. VI.1998 / В Мутин” , 1♂ ( JSA); same data as previous, except “ 8.06.2001 ” , 1♂ ( VMK); “Komsomolsk-na- / Amure / Central district / 21. VI 1999 Mutin” , 1♂ ( MRL); same data as previous, except “ 8. VI.1998 V. Mutin ” , 1♂ ( MRL); “Комсомолск-на-Амуре / Силинский парк / Тенлый кпюч / 31.05.2014 / В. Мутин” , 1♀ ( VMK); “RUS- SIA 20 km S. of Khabarovsk / City, Bychikha / Crateagus maximowitchi / 02 06 2015 V. A. Mutin ” , 1♂ ( VMK); same data as previous , 1♀ ( JSA); “ Ru Хабаровский край / окрестности Пивань / смешанный лес / В Мутин / 01.06.2014 ” , 1♂ ( SBH); “ Хабаровский край / окрестности Хабаровска / р. Чирки / 05.06.2017 В. Мутин”, “ Myolepta sub-group / fig no JvSMo1-010” , 1♂ ( VMK); “Хабаровский кр. / Пивань / 4.06.2006 / В. Мутин” , 1♀ ( JSA); “ЮЖное Приморье / бух. ВитЯЗь / 5. VI.2006 / М. ПроЩалыкин” , 1♂ ( VKM); “ЮЖ. Приморье окр. с. / Каменушка / ув. Acer ginnala / 15. VI Мутин 981г.” , 1♂ ( JSA); same data as previous, except “13. VI ” , 1♀ ( VMK); “ЛаЗовский Зап / верх р Быструшка / 14- 17.06.2007 / Ю. Сундуков” , 1♀ ( VMK); “ Russia, Siberia / Novosibirskaya Oblast / Berdsk , Shadriha river / 54°46’N 83°09’E / 22-06- 2013, 115 m a.s.l. / J van Steenis Sib13- 658”, “ Myolepta sub-group / fig no JvSMo1-006” , 1♀ ( JSA); “п. ТанЗыбей // стационвр ИЛ // Смешнный лес // пцхтарник // Колл. Е. В. Борисова // 14.06.10” , 1♂, 1♀ ( JSA); “ Зап. СаЯн окр. г. // АбаЗа 11. VI.1981 // Сб. А. Баркалов” , 1♂ ( SZMN); [written Russian alphabet, hardly readable] “6/VII.75” , 1♂ ( SZMN); “Симоново Амур. обл. // 75 km W. Свободного // Зиповьев 8. VI.959”, “illegible // на уь Salix // xerophila ”, “коллекциЯ // Н. А. Виоловичь” , 1♂ ( SZMN); “окр. Горно Алтайска // 23-25. VI.1979 // сб. А. Баркалов” , 1♀ ( SZMN); “ст Сица Сучан. рн. // Уссур. кр. 15. VI // Штакелберг 927” , 1♀ ( SZMN); “рр. М. Пера Б. Эрг- // ель меЖдур Амур. // Зиновев ьирубка 10. VI.1958 ”, “XV 2-1 // ъирубка” , 1♀ ( SZMN) .

Diagnosis. Face in male with shiny vitta from central knob down to mouth edge; face relatively narrow at height of mouth edge; frons in female with narrow light-grey pollinose fascia along eye margin reaching posteriorly not as far as anterior ocellus; scutum with rather short yellowish pile; pleura predominantly non-pollinose and shiny, only parts of proepimeron, anterior anepisternum, katepisternum and anepimeron grey-pollinose slightly shiny; tergum II evenly shiny, almost entirely non-pollinose; sterna entirely pollinose.

Description. MALE. Body length 9.5–12.2 mm, wing length 7.9–10.7 mm. Head. Face slightly protruding antero-ventrally and concave, with clear central knob; frons triangular, slightly less protruding than mouth edge; grey-brown pollinose and dull, except for the following non-pollinose and shiny parts; a fascia from central knob down to mouth edge and a triangular area laterally from mouth edge to eye margin; frons wide, black shiny, only grey pollinose along eye margin; pile on frons yellow, confined to the pollinose part; ocellar triangle black, shiny, yellowish pilose. Thorax. Scutum with erect to slightly reclined and rather short yellowish pile, this pile clearly shorter than on posterior margin of scutellum; anterior margin of scutum rather broadly grey-pollinose; postpronotum pollinose on anterior 1/2 to 3/4; pleura black, predominantly shiny and with rather long light yellow pile, non-pollinose and shiny, except pollinose and dull to sub-shiny on proepimeron, on postero-dorsal half of anterior anepisternum, on posterior half of anepisternum, on entire anepimeron and postero-ventrally and on postero-dorsal corner of katepisternum; pile on katatergum thin, very dense and short; non-shiny grey-pollinose parts confined to anterior 3/4 of proepimeron, anterior margin of anterior anepisternum, posterior 1/3 of anepisternum and posterodorsal corner of katepisternum; scutellum black, shiny, long yellow pilose. Wing. Shape, veins and cells as usual for the genus with yellow basal veins and darkly infuscated at stigma and apically; basal wing cells extensively bare of microtrichia; vein Rs and basal part of vein R 1 with a row of rather long setae. Legs. Colour predominantly black, except: knees yellow; pro- and mesotrochanter in most specimens entirely yellow; protibia only narrowly yellow basally and apically; meso- and metatibia variable but often widely yellow basally and apically; first three tarsomeres of meso- and metatarsus yellow; pile on legs almost entirely yellow; black setulae present on baso-ventral part of femora, ventral side of pro- and mesotarsus and ventrally at apex of mesotibia; longest pile on ventral side of metafemur short, about half as long as width of metafemur. Abdomen. Entirely black, predominantly light-yellow pilose; terga I–III medially and tergum IV antero-medially with short and suppressed black pile; yellow pile on lateral margin of terga rather long, on terga II and III rather short and on tergum IV sub appressed on posterior half; terga mostly shiny, non-pollinose except anterior margin of tergum II slightly pollinose but shiny and tergum I entirely densely grey-pollinose and non-shiny; sterna with long white pile, entirely greyish-brown pollinose, dull. Genitalia ( Figs 3 A–C). Epandrium squarish with postero-dorsal corner more medially placed; cerci rounded, yellow pilose, pile about as long as width of cercus; surstylus short rectangular shaped with straight ventral margin, slightly concave dorsal margin and almost squarish apex, ventral half and along ventral margin covered with short black setae, dorsally with short yellow pile; hypandrium elongate, rectangular, apico-ventrally rounded into narrower apex, in ventral view basally rounded with round medio-lateral corners, apical part only slightly narrower; superior lobe separated from hypandrium by a apico-ventral cleft and a baso-dorsal membranous area; superior lobe rectangular with deep and sharp incision apico-ventrally and rounded apico-dorsally; baso-dorsally with short and rather wide triangular extension; aedeagus oval-shaped ventral margin rounded apically; dorsal margin basally and apically with small rounded extension.

FEMALE. Body length 8.1–10.5 mm, wing length 5.7–8.1 mm. Similar to male except for sexual dimorphism. Face strongly concave, without central knob; black, largely non-pollinose and shiny; a wide trapezoid area from just below the antennae down to mouth-edge and a broad triangular area laterally from the mouth edge to the eye margin non-pollinose; frons rather wide with narrow rather short grey pollinose fascia along eye margin, ending posteriorly clearly before ocellar triangle.

Etymology. The specific epithet “ angustifacia ” is composed of the Latin words ‘ angustus ’ (narrow) and ‘ facius ’ (face), referring to the relatively narrow ventral part of the face in the male.

Distribution. Widespread in the Eastern parts of the Siberian lowlands from the Altai to the Russian Far East.

Biology. The larva has been described, as Myolepta vara , based on a larva found in a rot-hole in Ulmus pumila L. in Komsomolsk-on-Amur ( Sivova et al. 1999). Adults were found in moist mixed taiga forests with streams and rivers nearby. Adults have been collected while visiting flowers of Crataegus maximowiczii C.K. Schneid. and Salix xerophila Flod.

Remarks. Very similar to Myolepta vara and M. shikokuana based on the pilose metasternum, the relatively short-pilose scutum and metafemur and the narrow pollinose area along the eyes in the female. Differing from M. vara in the more pollinose face, pleura and sterna and the slightly narrower ventral part of the face; and from M. shikokuana by the less pollinose face and pleura, the clearly narrower ventral part of the face and the shorter pile on postero-ventral part of the metafemur. Furthermore, the surstylus and hypandrium in ventral view are differently shaped in all three species in which M. angustifacia sp. n. has a relatively short and basally broad surstylus with slightly triangular apex and hypandrium with round medio-lateral corners, M. shikokuana a slightly more elongate, medially wide surstylus with rounded apex and the hypandrium similar to M. angustifacia sp. n. and M. vara with an elongate, dorsally straight surstylus with rounded apex and hypandrium with very weak medio-lateral corners. Siberian specimens previously identified as M. vara are most likely to all belong to this new species.

Figures

FIGURE 1. Adult habitus of Myolepta hoverflies, male; A, C dorsal view; B, D. lateral view. A, B. Myolpeta angustifacia sp. n., holotype, fig no JvSMo1-001. C, D. Myolepta nigra, Douglas Co, Canada, fig no JvSMo1-002. Scale 1.0 mm.

FIGURE 3. Male genitalia Myolpeta angustifacia sp. n., holotype, fig no JvSMo1-001. A. lateral view. B. aedeagus, lateral view. C. hypandrium, ventral view. Scale 0.5 mm.