Romaleosyrphus Bigot, 1882

Moran, Kevin M. & Skevington, Jeffrey H., 2021, Taxonomic revision of Romaleosyrphus Bigot (Diptera, Syrphidae), including descriptions of seven new species, ZooKeys 1075, pp. 1-32 : 1

Romaleosyrphus Bigot, 1882

Figures 1 , 2 , 3

Romaleosyrphus Bigot, 1882a: 159. - Bigot (1882b): cxxix; - Bigot (1883): 356. Type species: Romaleosyrphus villosus Bigot, 1882 by original designation.

Rhomaleosyrphus Rye, 1884: 10. - Kertész (1910): 291. Unjustified emendation of Romaleosyrphus .

Crioprora Williston, 1891: 73. - Aldrich (1905): 401. - Coquillett (1910): 528.

Criorhina Thompson, 1976: 118.

Differential diagnosis.

Romaleosyrphus is separated from Criorhina and Sphecomyia by the combination of the following characters. Male eye contiguous for ca. 1/2 length of ocellar triangle. Oval shaped postpedical. Broad intersection of vein R1 with vein C. Proximal ventral half of vein C with setae. Abdominal pile appressed. Male genitalia with phallapodeme keeled and laterally sclerotized, not banana-shaped. It is further distinguished from Matsumyia by a distal part of vein R4+5 beyond vein M1 longer than cross-vein h.

Redescription.

MALE. Body length: 13.0-17.1 mm. Wing length: 8.0-12.1 mm.

Head. Face black, produced downwards and completely pruinose, concave beneath antenna, tuberculate; gena broad, as broad or broader than long, bare, shiny, pilose posteriorly; anterior tentorial pit short, extending along ventral third of eye, pilose; frontal prominence distinct; frons broad and pruinose; vertex triangular, longer than broad and always pilose; ocellar triangle small; eye bare, contiguous for ca. 1/2 length of ocellar triangle; head oval in shape; length of antenna segments in a 3:3:2 ratio; postpedical oval, with bare arista dorsally placed.

Thorax. Ca. as long as broad, long pilose; postpronotum pilose; proepimeron pilose; anterior anepisternum bare, posterior anepisternum pilose; scutellum without apical sulcus and with ventral pile fringe; katepisternum bare anteriorly, discontinuously pilose posteriorly with broadly separated patches; anepimeron with anterior portion pilose, and dorsomedial and posterior portion bare; katepimeron bare; metathoracic pleuron bare; without hypopleural pile at the base of the posterior thoracic spiracle; meron bare; metathoracic spiracle ca. same size as postpedical; metasternum pilose; postmetacoxal bridge incomplete; plumula simple, elongate, short, not reaching calypteral margin; calypter brown.

Legs. Coxae pilose anteriorly, bare posteriorly; hind trochanter sometimes tuberculate in male; metafemur swollen, curved, with large apicoventral ridge and without basiventral setose patch; metatibia transverse apically, rounded basiventrally.

Wing. Cell r1 open; stigmatic cross vein present; cross-vein r-m at outer ¼ of cell dm; broad intersection of vein R1 with vein C (Fig. 3 ); vein R4+5 straight; distance between apices of veins R1 and R2+3 longer than distance between apices of veins R2+3 and vein R4+5; distal part of vein R4+5 beyond vein M1 (hereafter distal vein R4+5) longer than cross-vein h (Fig. 3 ); vein M2 absent; vein CuP+CuA short, curved; proximal ventral half of vein C with setae.

Abdomen. Oval, slightly longer than broad, with dense appressed pile.

Male genitalia. Surstyli symmetric; aedeagus segmented, with phallapodeme separated from basiphallus and distiphallus; phallapodeme rounded, not banana-shaped; well-developed ctenidion present in male genitalia.

FEMALE. As male except for the following character states. Eyes widely separated; frons fully brown pruinose; face without pruinosity; metafemur only slightly swollen, never curved or with apicoventral ridge; metatibia never modified; always without tubercle on hind trochanter; wing always less microtrichose with species-specific characters as in species description.

Remarks.

Generally, species of Romaleosyrphus show little variation in pile color patterns, at least given the limited material we worked with. However, there are a few exceptions. Romaleosyrphus soletluna Moran & Thompson, sp. nov. is drastically dimorphic in pile coloration with a mostly orange morph and mostly black morph. The single northern specimen of Romaleosyrphus arctophiloides from the Sierra Madre Occidental has fully black pilose legs. This contrasts with the population surrounding Mexico City, from which the type was collected, which have a streak of yellow pile at the base of the fore and mid femora. Finally, pile color on the proepimeron is variable inside multiple species with observed character states being fully yellow, fully black or a mix of the two. We suspect that additional material will likely show proepimeron pile color to be variable in all species.

Figures

Figure 1. Romaleosyrphus bigoti sp. nov.

Figure 2. Romaleosyrphus distribution.

Figure 3. Intersection of vein R 1 with vein C (white), distance between apices of veins R 1 and R 2 + 3 and apices of veins R 2 + 3 and R 4 + 5 (blue), distal vein R 4 + 5 (pink) and setosity of proximal ventral half of vein C (red). A Romaleosyrphus bigoti sp. nov. B Sphecomyia weismani (Moran) C Criorhina bubulcus (Walker).