Mesoconius obtusiconus Enderlein, 1922

Marshall, Stephen A., 2019, A revision of the genus Mesoconius Enderlein (Diptera, Micropezidae, Taeniapterinae), European Journal of Taxonomy 548, pp. 1-126 : 40-43

Mesoconius obtusiconus Enderlein, 1922

Fig. 14

Mesoconius obtusiconus Enderlein, 1922: 179 .

Material examined

Holotype

PERU • ♀; Cusco, Callanga, Piñipiñi Valley ; 1500 m a.s.l.; O. Garlepp leg.; MNBG.

Other material

COLOMBIA • ♀; Nariño, La Planada Nature Reserve Parcela Permanente; 01°15ʹ N, 78°15ʹ W; 1885 m a.s.l.; 2–16 Jun. 2001; G. Oliva leg.; Malaise trap; M2382; IAVH .

Description

Described based on Colombian non-type specimen (female) except as noted.

LENGTH. 17 mm.

COLOUR. Abdomen orange at base (T1–2 or T1–3), otherwise black; thorax mostly black, metapleuron and scutellum orange on Colombian specimen but not on type. Head black, except as follows: gena, extreme anteroventral corner of face and parafacial silvery microtrichose, palpus orange-brown, margin and postocellar part of frontal vitta silvery microtrichose, scutum with a silvery longitudinal vitta on each side, presutural part of silver strip narrow and tapered anteriorly, postsutural part broader and split to create a diffuse, central dark patch. Fore tarsus white (type with base of tarsomere 1 and all of tarsomeres 4–5 darkened), hind tarsus white, with mostly white setae on tarsomeres 1–4, dark setae on tarsomere 5 (hind tarsus missing on Colombian specimen); fore femur orange basally, black distally; mid femur sharply divided into orange basal and black distal half; hind femur similarly divided, but with a white band near base of distal black part. Tibiae black. Wing clear except for indistinct broad discal and apical bands. Oviscape black. Pleuron pale except for slightly darkened upper halves of pleura 3–6.

HEAD. Epicephalon and paracephalon bare and shiny, indistinctly striate, sharply contrasting with dull striate orbits and lower frons; frontal vitta broad anterior to ocelli (0.44 × frontal width), constricted behind ocelli to form a broad, microtrichose, parallel-sided band. Fronto-orbital bristles (2) widely separated, upper fronto-orbital bristle very large, inserted on epicephalon well above orbital strip, lower fronto-orbital minute. Upper face flat, except for a narrow central carina, subantennal areas shiny.

THORAX. Cervical sclerite with a vertical groove separating a microtrichose, subquadrate, dark and convex posterior portion from a small, bare, pale anterior portion. Scutum with microtrichose pattern of silvery areas as noted above, otherwise unevenly microtrichose, broad central vitta with a narrow long-microtrichose vitta flanked by scattered small acrostichal setulae near middle; dorsocentral setulae minute, but forming a row; postpronotal lobe microtrichose, except for shiny anterior fifth, which has many small setulae. Dorsocentral bristle strong, longer than scutellum. Katatergite slightly swollen, entirely setulose, without a point or prominent apex. Vertical row of katepisternal bristles yellow. Coxae with black anteroventral setae.

ABDOMEN. Abdominal segments 1 and 2 petiolate; length of 1+2 2.4× that of tergite 3. Bursa with a small oval body bearing a finger-like ventral receptacle, distally extending as a broad common spermathecal duct. Single spermathecal duct arising just before apex of common spermathecal duct, uniformly smooth and parallel-sided until a constriction just before basally swollen and distally tapered single spermatheca. Paired spermathecal duct arising at apex of long common duct, entirely smooth and uniform from apex of striated common duct to constriction, before splitting into paired spermathecae and their stems. Paired spermathecae oval, distinctly striate, each stem with a large oval swelling and a distal section with an S-bend putting spermatheca at right angle to duct. Single spermathecal duct only slightly smaller than paired duct, spermatheca narrow but well developed.

Remarks

The holotype of M. obtusiconus , from Peru, and the specimen from Colombia differ in a number of details, including the distal fore tarsomeres (white in the Colombian specimen, dark in the type) and the colour of the metapleuron and hind coxa (red in the Colombian specimen, black in the type). Both specimens, however, share several distinctive characters, such as the colour of the mid and hind femora, the broad postocellar part of the frontal vitta, a similar pattern of silvery pruinosity on the scutum and a similarly reddish abdominal base. Furthermore, they easily key out together because of the distinctive femoral colour. More specimens of this species (or species group) are needed to clarify what variation is intraspecific and what is interspecific.

This is one of the five species originally described in Mesoconius solely on the basis of specimens from Callanga, Peru. Two remain known only from the types. The other three, M. obtusiconus , M. albimanus Enderlein, 1922 and M. infestus Enderlein, 1922 present similar problems because of differences between the Callanga material and putatively conspecific material from Colombia.

Mesoconius obtusiconus is unusual because the absence of a postocellar bristle places it in the M. eques group, but the relatively flat katatergite and the spermathecal complex resemble those of the M. oblitus group.

Figures

Fig. 14. Mesoconius obtusiconus Enderlein, 1922, ♀♀. A. Spermathecae and associated structures, dorsal view, Colombia. B. Oviscape with spermathecae teased out, Colombia. C. Spermathecae and associated structures, lateral view, Colombia. D–E. Holotype, MNBG, Peru. F. Entire specimen, Colombia. G. Head, Colombia. Abbreviations: bc = bursa copulatrix; cd = common duct; ps = paired spermatheca; psd = paired spermathecal duct; pss = paired spermathecal stem; ss = single spermatheca; vr = ventral receptacle.