Merodon mixtum Vujić, Radenković et Likov, 2019

Vujić, Ante, Radenković, Snežana, Likov, Laura, Andrić, Andrijana, Gilasian, Ebrahim & Barkalov, Anatolij, 2019, Two new enigmatic species of the genus Merodon Meigen (Diptera: Syrphidae) from the north-eastern Middle East, Zootaxa 4555 (2), pp. 187-208 : 192-199

Merodon mixtum Vujić, Radenković et Likov sp. n.

Figs 8 , 9 , 10 , 11A , 12 A–B, 13, 15

Type material. HOLOTYPE: Iran, ♂, pinned, in HMIM. Original label: “Iran, Golestan, Khanbebin, Shirabad, 80m, 5.vii.2001, Mofidi, Osten, Ebrahimi” . PARATYPES: Iran: 1♀, Golestan, Khanbebin, Shirabad , 80m, 36° 58' 51.13"N 55° 00' 6.7"E, 5.vii.2001, Mofidi, Osten, Ebrahimi ( HMIM) ; 1♂, Elburz Mountains, Mazandran, Haraz Chay river valley, 22 km S of Amol, 400m, 36° 23'N 52° 20'E, 23–24.vii.1970, det. by Bankowska as M. trochantericus ( NMPC) ; 2♀, Mazandaran, Behshahr , 36° 43'N, 53° 34'E, 25.vii.1970, det. by Bankowska as M. trochantericus ( NMPC) .

Diagnosis. Based on the bent anterior surstyle lobe of the male genitalia ( Fig. 13A ) and the mesocoxa posteriorly having many long pile, this species belongs to the M. albifrons lineage. This species has a unique combination of characters on the legs, including: apomorphic modifications on pro- and mesotibiae and pro- and metafemora in males ( Figs 10 A–D), less expressed in females ( Fig. 15B ); males with small thorn on the metatrochanter; ventral margin of metafemur undulating, with basal bulge and oval central process ( Fig. 11A ). Medium sized species (11–13mm), with vitta of black pile between wing bases. Tergum 4 with golden pilosity ( Fig. 12A ).

Description. MALE. Head ( Figs 8 A–B). Antenna dark brown-reddish ( Fig. 8A ); basoflagellomere with medium-sized fossette at dorsal surface, 1.2 times longer than pedicel, acute at tip; arista light brown in basal half and darker at the tip, covered with pollinosity, about as long as basoflagellomere and pedicel together. Face and frons black, covered with yellow pile and dark grey pollinosity, except for shiny gena and upper and lower parts of mouth edge; occiput covered with dense grey pollinosity and with pale-yellow pile. Eyes densely covered with pale pile, about as long as posterior ocellus. Eye contiguity about 10 facets long. Vertex black, covered with yellow pile, except for ocellar triangle covered with long black pile; vertical triangle isosceles, covered with greyish pollinosity; ocellar triangle isosceles, posterior ocelli larger than anterior ocellus ( Fig. 8B ). Thorax ( Figs 9 , 10 , 11A ). Scutum black, with three narrow pollinose vittae; scutum mostly covered with pale-yellow pile, except for wide fascia of mixed yellow and black pile between wing bases ( Fig. 9 ); posterior margin of scutum shiny. Scutellum black and shiny, covered with long pale-yellow pile, as long as half the width of scutellum or longer; posterior margin of scutellum with well-defined rim, lighter brown color compared to scutellum ( Fig. 9A ). Wings hyaline, mostly covered with microtrichia, except for basal part of cell r; vein RS with a few short pale pile at the beginning of cell r2+3; veins dark brown, haltere yellow-brown. Pleuron black; dorsal part of anterior anepisternum, posterior anepisternum, anterior anepimeron, dorsomedial anepimeron, posterior anepimeron and posterodorsal and anteroventral parts of katepisternum covered with long pale pile, whereas katatergum is covered with short brown pile. Femora black, except for yellow tip, tibiae yellow except for brown apical third of pro- and mesotibia and central part of metatibia; apical two tarsomeres black dorsally, whereas the other tarsomeres are yellow on all legs; legs covered with yellow pile, but pile on bulges of metafemur and on metatrochanter orange-red; metatrochanter with a small thorn-like process that is densely covered with short orange pile; apical third of pro- and mesotibia twisted ( Figs 10 A–B); bulge located at middle third of pro- and mesofemora and in basal third of mesofemur; one large bulge basoventrally at the inner side and one acute bulge at basal half of metafemur, both covered with conspicuously orange-red pile ( Figs 10 , 11A ); metafemur with bare line ventrally and with a row of orange-red pile opposite to triangular process at apicoventral part of metafemur. Abdomen ( Fig. 12A ). Terga mostly black; tergum 2 with a pair of yellow triangular maculae and yellow pile on lateral margins; tergum 3 with short black pile on dorsal surface and fascia of pale ones at posterior margin; terga 2 and 3 with a pair of triangular pollinose fasciae covered with yellow pile; tergum 4 entirely covered with short yellow-golden pile, and with a pair of connected pollinose fasciae in the middle of the tergum. Sterna 2–3 light brown, sterna 1 and 4 dark, all covered with pale pile; posterior margin of sternum 4 with rounded medial incision. Male genitalia ( Figs 13 A–C). Posterior surstyle lobe broad, with parallel margins and rounded apex, curved interiorly (marked on Fig. 13B ); anterior surstyle lobe bent inward, narrow, covered with dense short pile; cercus elongated ( Figs 13 A–B). Hypandrium sickle-shaped; lateral sclerite of aedeagus well developed, hammer-shaped ( Fig. 13C ).

FEMALE ( Figs 8 C–D, 15A–B). Similar to the male except for typical sexual dimorphism and for the following characters: frons shiny, with broad pollinose vittae along eye margins; ventral margin of antennae light brown ( Figs 8 C–D); anterior half of scutum covered with pale- yellow pile; pro- and mesofemora with slight depression at apical end; metafemur simple except for barely visible bulge ventrally in the middle of the femur ( Fig. 15B ); pro- and mesotibiae with tooth in apical third and with black maculae basolaterally. Terga 4–5 with pale pollinose fasciae at posterior margin ( Fig. 15A ). Sterna dark, except for yellow sternum 2, posterior margin of sternum 4 and anterior half of sternum 3.

Etymology. The specific epithet ‘ mixtum ’ derives from the Latin adverb ‘ mixtim ’ meaning ‘in a mixed way’, since this species shows characters of different species groups.

Distribution. Mountainous area in northeast Iran ( Fig. 16 ).

Morphological characters in common with different species groups of the albifrons lineage. Merodon albifrons + desuturinus lineage (sensu Vujić et al. 2012) is divided in two lineages, M. albifrons and M. desuturinus ( Table 1). M. albifrons lineage contains six groups and two individual taxa ( Table 1) with 64 species in total. Among these six groups, M. mixtum sp. n. shares some taxonomically important characters with four groups: M. constans , M. albifrons , M. geniculatus , and M. ruficornis .

Merodon mixtum sp. n. — Merodon constans group. The M. constans group is defined by the following combination of characters: medium to large-sized hoverflies (7–16 mm); tip of abdomen (or at least tergum 4) covered with golden to reddish-yellow pile ( Figs 12 C-D); terga reddish to black; terga 2–4 (or at least tergum 4) with a pair of usually triangular pollinose fasciae ( Figs 12 C–D); scutum often with black pile between wing bases; male usually with projections on metalegs (on apex of tibia and ventral margin of femur) (as on Fig. 11A ).

The character that links Merodon mixtum sp. n. with all species belonging to the M. constans group is the golden pilosity on the top of the abdomen (tergite 4) ( Fig. 12A ). Some species of the M. constans group, such as M. caucasicus Portschinsky , possess a small thorn on the metatrochanter and exhibit a central bulge on the ventral side of the metafemur ( Fig. 11E ), similar to M. mixtum sp. n. Male genitalia of M. mixtum sp. n. ( Fig. 13A ) and M. caucasicus ( Fig. 14B ) are very similar in shape, especially in terms of the surstyle and cercus.

Merodon mixtum sp. n. — M. albifrons group. The M. albifrons group possesses the following combination of morphological features: medium-sized hoverflies (7–12 mm); terga at least partly reddish; terga 2–4 usually with a pair of pollinose fasciae; male without projections or thorns on metalegs, except for M. trochantericus Costa ( Fig. 11C ); characteristic thorn-like process on the posterior surstyle lobe of the male genitalia ( Fig. 14C ).

One representative of the Merodon albifrons group, M. trochantericus , is similar to M. mixtum sp. n. in having a similarly shaped posterior surstyle lobe ( Fig. 14D ), a small thorn on the metatrochanter ( Fig. 11C ), and a small basal bulge at the posterior margin of the metafemur ( Fig. 11C ).

Merodon mixtum sp. n. — M. geniculatus group. The following combination of characters distinguishes the M. geniculatus group from other groups within the M. albifrons lineage: tergum 2 with a pair of reddish lateral maculae; metatrochanter in males with a blunt thorn, usually covered with a tuft of pile ( Fig. 11B ); metatibia in apical third strongly curved, with broad tip; posterior surstyle lobe oval or triangular ( Fig. 14E ). All species of the M. geniculatus group have a well-defined thorn on the metatrochanter ( Fig. 11B ) that is similar in shape to that of M. mixtum sp. n. ( Fig. 11A ).

Merodon mixtum sp. n. — M. ruficornis group. The M. ruficornis group exhibits several synapomorphic characters, especially in terms of the structure of the metalegs in males (trochanter, femur and tibia of metaleg usually with processes, Fig. 11D ). Furthermore, the posterior surstyle lobe of the male genitalia is characteristically hook-like ( Fig. 14F ). In females, tergum 4 has a transversal depression; terga are dark, except for tergum 2 with a pair of red-orange lateral maculae; terga 2–4 with a pair of white pollinose fasciae; tergum 5 with two small lateral depressions; and vertex at the level of the ocellar triangle is shiny black. Most species of the M. ruficornis group have a thorn on the metatrochanter and possess a central bulge at the ventral margin of the metafemur ( Fig. 11D ) that is similar in shape to that observed in M. mixtum sp. n. ( Fig. 11A ).

Figures

FIGURE 8. Head of Merodon mixtum sp. n.. A, C lateral view, B, D dorsal view. A, B male, C, D female. Scale bar, 1 mm.

FIGURE 9. Male of Merodon mixtum sp. n.. A dorsal view, B lateral view. Scale bar, 1 mm.

FIGURE 10. Legs of male in Merodon mixtum sp. n.. A profemur and protibia, B mesofemur and mesotibia, C metafemur and metatibia, A-C anterior view, D ventral view. Scale bar, 1 mm.

FIGURE 11. Metatrochanter and metafemur of Merodon male, anterior view. A Merodon mixtum sp. n., B Merodon geniculatus Strobl, C Merodon trochantericus, D Merodon trebevicensis Strobl, E Merodon caucasicus. t—thorn on trochanter, bb—basal bulge, cb—central bulge. Scale bar, 1 mm.

FIGURE 12. Abdomen of male. A, B Merodon mixtum sp. n., C Merodon constans (Rossi), D Merodon chrysotrichos. A, C, D dorsal view, B sterna 4, ventral view. Scale bar, 1 mm.

FIGURE 13. Male genitalia of Merodon mixtum sp. n.. A, B epandrium, C hypandrium. A, C lateral view, B ventral view. al— anterior surstyle lobe, pl—posterior surstyle lobe, c—cercus, s—lateral sclerite of aedeagus. Scale bar, 0.5 mm.

FIGURE 14. Male genitalia of Merodon, epandrium, lateral view. A Merodon constans, B Merodon caucasicus, C Merodon albifrons Meigen, D Merodon trochantericus, E Merodon geniculatus, F Merodon ruficornis Meigen. p—thorn-like process.

FIGURE 15. Female of Merodon mixtum sp. n., A habitus, dorsal view, B hind leg, anterior view. Scale bar, 1 mm.

FIGURE 16. Distribution map of Merodon eumerusi sp. n. and Merodon mixtum sp. n. (KG—Kyrgyzstan, TJ—Tajikistan).