Mesoconius eques ( Schiner, 1868 ) Marshall, 2019

Marshall, Stephen A., 2019, A revision of the genus Mesoconius Enderlein (Diptera, Micropezidae, Taeniapterinae), European Journal of Taxonomy 548, pp. 1-126 : 30-31

Mesoconius eques ( Schiner, 1868) comb. nov.

Fig. 9 A–C, D (in part), E–I

Calobata eques Schiner, 1868: 251 .

Mesoconius aeripennis Enderlein, 1922: 180 . syn. nov.

Cliobata eques – Steyskal 1968 : 48.6.

Material examined

Type material of Calobata eques Schiner, 1868

VENEZUELA • ♂ (probable type); “ eques, Alta Sammlung ”; “Venezuela”; “ Mesoconius End. F. Hendel det.”; NHMW.

Holotype of Mesoconius aeripennis Enderlein, 1922

ECUADOR • ♀; Baños; R. Haensch leg.; MNBG.

Other material

ECUADOR • 4 ♂♂, 8 ♀♀; Napo, SierrAzul Reserve , 14 km W of Cosanga; 2200 m a.s.l.; 00°40ʹ55ʺ S, 77°56ʹ9ʺ W; 10 May 2002; M. Buck leg.; DEBU • 2 ♂♂, 3 ♀♀; same locality as preceding; 11 May 2002; M. Buck leg.; DEBU • 6 ♂♂, 2 ♀♀; same locality as preceding; 8–11 May 2002; S.A. Marshall leg.; dung on leaf; DEBU • 4 ♂♂, 2 ♀♀; same locality as preceding; 8–11 May 2002; S.M. Paiero leg.; MYCRO074-15 sequenced for CO1; DEBU • 1 ♀; same locality as preceding; 8–11 May 2002; P. Careless leg.; DEBU • 1 ♂; same locality as preceding; 5 Nov. 1999; S.A. Marshall leg.; dung ball; DEBU • 1 ♀; Napo, Yanayacu ; 23–28 Jul. 2008; W.K. Reeves leg.; DEBU • 1 ♂; Napo, 4.2 km S of Cosanga , pipeline trail; 2150 m a.s.l.; 7 Nov. 1999; S.A. Marshall leg.; QCAZ .

Description

LENGTH. 16–18 mm.

COLOUR. Black, including wing membrane, except as follows: parafacials, gena and face strongly silvery microtrichose, inner and outer margins of subantennal areas shiny brown; mid and hind femur usually with white bands near or just beyond middle, bands vary from wide to obsolete. Notum with postsutural area silvery microtrichose, except at middle, pruinosity extending presuturally as two broad longitudinal vittae and sometimes a narrow median vitta. Abdominal pleuron dirty white.

HEAD. Epicephalon and paracephalon finely striate, subshining; frontal vitta velvety, posteriorly tapered to a broad, densely microtrichose patch extending to level of inner vertical bristles, broad and broadly tapered anteriorly, extending ⅔ of distance from ocellus to frons margin. One large fronto-orbital bristle, inserted at junction of epicephalon and orbital strip. Antennae separated by width of antennal socket, upper quarter of face strongly and broadly carinate, lower face flat. Clypeus mostly bare. Lower back of head densely short-setose.

THORAX. Cervical sclerite with a microtrichose, subquadrate posterior portion and a small bare anterior portion. Fore tibia narrow, sulcate on outer face. Tarsomere 1 of fore leg expanded and flat, much wider than and longer than other tarsomeres combined, very broad and cultriform in male, less conspicuously broadened in female. Mid and hind femora shiny and almost bare basal to pale band near midpoint, setulose and slightly swollen distally. Notum microtrichose, with rows of small acrostichal and dorsocentral setulae; postpronotal lobe microtrichose, with some scattered small setulae, anterior margin forming a vertical, shiny face. Dorsocentral bristle slightly longer than scutellar length. Scutellum with two–four small discal setulae and a pair of long apical bristles (longer than scutellum). Katatergite very prominent, with a long, tapered microtrichose nipple-like process. Notopleuron with two widely spaced black bristles. Vertical row of katepisternal bristles black. Coxae with anteroventral black setae.

ABDOMEN. Abdominal segment 1 and base of segment 2 petiolate; length of 1+2 twice as long as that of tergite 3.

FEMALE ABDOMEN. Bursa small, inconspicuous; ventral receptacle reduced; single spermatheca small, tuberculate, on a short duct arising from side of a long common duct that becomes basal part of paired spermathecal duct; paired spermathecae with a very long, broad duct divided into two parts: basal ⅔ broader, more membranous and accordian-like, distal part more sclerotized and with weak transverse striations and slightly swollen before splitting into strongly tuberculate stems leading to each spermatheca. Paired spermathecae cup-like, invaginated apically, with transverse striations.

MALE ABDOMEN. S5 small, unmodified. S6 tapered anteriorly, broad posteriorly, posterior margin with a deep V-shaped emargination. S7 broad, extending along hind margin of S6. S7–8 black, shiny except for dull, microtrichose posterior margin. Epandrium with large, quadrate, setose posteroventral angles, cercus large and in a more or less dorsal position. Hypandrium anteriorly forming a simple loop with a small and narrow anterior process. Basiphallus very small, frame-like; not extending beyond base of distiphallus. Basal part of distiphallus short, narrowly tubular, gradually expanding to a large phallic bulb; distal part of distiphallus 3× as long, terminating in a barb-like apex. Ejaculatory apodeme slightly smaller than epandrium.

Remarks

The unusual appearance of this species, which is almost entirely black including the wing membrane and abdominal pleuron, is matched by an undescribed species of Poecilotylus Hennig, 1934 ( Fig. 9D , in part) from the same locality in Ecuador where most of the specimens of Mesoconius eques examined here were collected. Mesoconius noteques sp. nov., from Peru, also resembles M. eques in external features other than the fore tarsi (slender in M. noteques sp. nov.), but is very different in the structure of the spermathecal ducts. The other almost entirely black species in the Mesoconius eques group, M. pasachoa sp. nov., has more extensive pale pigmentation on the tibiae and tarsi. The most remarkable external feature of M. eques is the expanded, paddle-like tarsomere 1, which is especially broad in the male but also conspicuously expanded in the female. The only congener with a similarly expanded male tarsomere is M. lobopoda sp. nov., in which the expanded tarsomere of males is brown on the outer surface and brilliantly white on the inner surface. Mesoconius lobopoda sp. nov. differs widely in other characters and does not belong to this species group. The type specimens of M. eques (described from Venezuela) and M. aeripennis (described from Ecuador) differ slightly, as the hind femur of the former has a white band and the hind femur of the latter appears to be immaculate. Most of the new material reported here (from Ecuador) seems identical to the type of M. eques (from Venezuela) but the band on the hind femur is reduced on some specimens. I see no other character that might justify recognizing M. aeripennis and M. eques as different species.

Figures

Fig. 9. Mesoconius eques (Schiner, 1868). A. Presumed holotype, ♂, NHMW, Venezuela. B. Live ♂, Ecuador. C. Head. D. ♀ (right) and a sympatric undescribed species of Poecilotylus Hennig, 1934 (left), Ecuador. E. Thorax-abdomen junction to show prominent katatergite. F. Base of phallus and distal part of phallapodeme, Ecuador. G. Abdomen, ♂, lateral view, Ecuador. H. Spermatheca and associated structures, Ecuador. I. Male aedeagus and associated structures, Ecuador. Abbreviations: bdp = basal distiphallus; cd = common spermathecal duct/distal bursa; ddp = distal distiphallus; ea = ejaculatory apodeme; ed = ejaculatory duct; hy = hypandrium; pb = phallic bulb; pd = paired spermathecal duct; ph = phallapodeme; pss = paired spermathecal stem; sd = single spermathecal duct.