Merodon ruficornis, Meigen, 1822

Vujić, Ante, Radenković, Snežana, Likov, Laura, Gorše, Iva, Djan, Mihajla, Ristić, Zlata Markov & Barkalov, Anatolii V., 2022, Three new species of the Merodon ruficornis group (Diptera: Syrphidae) discovered at the edge of its range, Zootaxa 5182 (4), pp. 301-347 : 305-307

The Merodon ruficornis group

Morphological diagnosis. The M. ruficornis group represents a morphologically distinct group of species with several synapomorphic characters, especially in the structure of male metaleg. Metatrochanter, metafemur and metatibia usually with tubercle, calcar or lamina in the male (as in Fig. 1 ). Male genitalia usually with characteristic hooklike posterior surstyle lobe (as in Fig. 2A : pl), biramous anterior surstyle lobe (as in Fig. 2A : al) with moderately developed interior accessory lobe (as in Fig. 2A : il) and apical extension (as in Fig. 2A marked with arrow), cercus without prominences (as in Fig. 2A : c), and lateral sclerite of the aedeagus hammer-like with oval margins (as in Fig. 9C : s). In females, tergum 4 usually with transversal depression (as in Fig. 3A : marked with arrow, 3B); terga dark, except tergum 2 with a pair of lateral red-orange maculae; terga 2–4 usually with a pair of white pollinose fasciate maculae; tergum 5 with two small lateral depressions (as in Fig. 3C : marked with arrow); vertex at the level of ocellar triangle shiny black (as in Fig. 3D ) ( Vujić et al. 2021a).

Morphological description of males and females of the M. ruficornis group. Length. We use the following three categories to describe the general body size of the species: Small species 7–10 mm; medium-sized species 10–12 mm; large species 12–14 mm. MALE. Head (as in Figs 4A–C ). Antenna (as in Fig. 4A ) brown-orange, basoflagellomere 1.3 times as long as wide, 1.6 times longer than pedicel, concave dorsally, apex acute; arista basally pale and thickened, brown medially and dark brown apically, 1.5 times longer than basoflagellomere; covered with short, dense microscopic pile. Face and frons black, covered with long whitish-yellow pile and silver pollinosity.

Oral margin shiny black, well protruded (as in Fig. 4A ). Vertical triangle (as in Fig. 4B ) isosceles, 2.5 times longer than eye contiguity, shiny black except in front of anterior ocellus white pollinose, covered with long whitish-yellow pile, except black pilose on ocellar triangle. Ocellar triangle (as in Fig. 4B ) equilateral to slightly isosceles. Eye contiguity about 8–10 facets long (as in Fig. 4C ). Eye pile as long as scape, pale. Occiput with whitish-yellow pile, along the eye margin dense, white pollinosity and posteriorly with metallic bluish-greenish lustre. Thorax. Mesonotum black with bronze lustre, covered with dense, erect, yellow pile, as long as basoflagellomere. Pleurae grey-green pollinose and the following parts with long yellow pilosity: anterior part of proepimeron, posterior part of anterior anepisternum, the larger part of posterior anepisternum except anterior end, anteroventral and posterodorsal part of katepisternum, anepimeron, metasternum; katatergum with dense, erect, short, light-brown pile. Wing hyaline, with dense, brown microtrichia. Calypter pale yellow. Halter with light brown pedicel and yellow capitulum (outer part dark). Femora dark brown to black, except usually paler apex; tibiae can be from completely dark to pale basally and apically; colour of tarsi variable. Metatrochanter (as in Fig. 1B : a) with calcar. Metafemur (as in Fig. 1B : b) thickened and curved, often with ventral tubercle (as in Fig. 1A : marked with arrow) in the basal 1/3 of its length. Metatibia (as in Fig. 1B : c) with apical lamina and/or spur(s). Abdomen (as in Figs 5A, C ). Black with bronze reflections, slightly tapering, as long as mesonotum. Terga 2–4 black with more or less distinct pair of white pollinose fasciate maculae (absent in some species); tergum 2 with a pair of orange anterolateral maculae; pile on terga mainly erect and yellow, but terga 2–4 medially usually with some black pile. Sterna blackish-brown, covered with long, pale yellow pile. Genitalia. Posterior surstyle lobe rounded, pointed anteriorly (as in Fig. 2A : pl); margin of surstylus convex (as in Fig. 2A ); anterior surstyle lobe with small interior accessory lobe (as in Fig. 2D : il); cercus oval or rectangular (as in Fig. 2A : c). Hypandrium with folded thecal ridge (as in Fig. 2C : marked with arrow). Lateral sclerite of aedeagus elongated and narrow, hammer-like in lateral view (as in Fig. 9C : s).

FEMALE. Similar to the male except for the normal sexual dimorphism and for the following characteristics: tergum 4 with transversal depression (as in Fig. 3A : marked with arrow, 3B); tergum 5 with two small, lateral depressions (as in Fig. 3C : marked with arrow); black pile on terga more conspicuous than in males: posterior margin of tergum 2, and terga 3–4 predominantly black pilose, except lateral sides and white pollinose fasciate maculae with pale pile.

Figures

FIGURE 1. Part of metaleg of Merodon male. A Merodon armipes (ventral tubercle marked with arrow), B M. acutus sp. nov. (ventral tubercle marked with black arrow; lamella on metatibia marked with white arrow), C M. nigripodus (lamella on metatibia marked with arrow), D M. ponticus (lamella on metatibia marked with arrow), E M. acutus sp. nov. (inner, posteroventral spina on metatibia, marked with arrow). a—metatrochanter, b—metafemur, c—metatibia. Scale bar: A–D 1 mm, E 1.5 mm.

FIGURE 2. Male genitalia. A, C, D Merodon acutus sp. nov., B, E M. nigripodus. A epandrium, lateral view (extension marked with arrow), B surstylus, lateral view (extension marked with arrow), C hypandrium, lateral view (folded thecal ridge marked with arrow), D, E surstylus, ventral view. al—anterior surstyle lobe, c—cercus, il—interior accessory lobe, pl—posterior surstyle lobe, s—lateral sclerite of the aedeagus. Scale bar: 0.25 mm.

FIGURE 3. Merodon female. A M. portschinskyi, T4, lateral view, B M. trispinus sp. nov., T4, lateral view, tergum 5 dorsal. C M. trispinus sp. nov., T5, frontal view (depression marked with arrow), D M. trispinus sp. nov., frons, dorsal view. Scale bar: A, B 0.8 mm, C 1mm, D 0.6 mm.

FIGURE 4. Head of Merodon trispinus sp. nov.. A–C male, D–F female. A, D lateral view, B, E dorsal view, C, F frontal view. Scale bar: A, D 0.5 mm, B, C, E, F 0.75 mm.

FIGURE 5. Abdomen of Merodon, dorsal view. A, B M. fulvitarsis sp. nov., C, D M. trispinus sp. nov.. A, C male, B, D female. Scale bar: A, D 1 mm, B, C 0.9 mm.

FIGURE 9. Male genitalia. A, C, D Merodon fulvitarsis sp. nov., B, E M. lamellatus. A epandrium, lateral view (extension marked with arrow), B surstylus, lateral view (extension marked with arrow), C hypandrium, lateral view (folded thecal ridge marked with arrow), D, E surstylus, ventral view.al—anterior surstyle lobe, c—cercus, il—interior accessory lobe, pl—posterior surstyle lobe, s—lateral sclerite of the aedeagus. Scale bar: 0.25 mm.