Mesoconius nigricephala, Marshall, 2019

Marshall, Stephen A., 2019, A revision of the genus Mesoconius Enderlein (Diptera, Micropezidae, Taeniapterinae), European Journal of Taxonomy 548, pp. 1-126 : 66-69

Mesoconius nigricephala sp. nov.

urn:lsid:zoobank.org:act:B8C1945B-451B-4BE0-B5B2-9DDDA57B9F52

Fig. 26

Etymology

The specific name refers to the dark head that contrasts with the mostly orange body of this distinctive species.

Material examined

Holotype

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

Paratypes

COLOMBIA • 1 ♀; same collecting data as for holotype; IAVH • 2 ♀♀; same collecting data as for holotype but 16 Mar.–2 Apr. 2001; IAVH • 1 ♀; Nariño, La Planada Nature Reserve, Via Hondon ; 01°15ʹ N, 78°15ʹ W; 1930 m a.s.l.; 16 Jun.–2 Jul. 2000; G. Oliva leg.; IAVH .

ECUADOR • 1 ♀ (photograph); Pichincha, Maquipucuna Biological Reserve ; 00°7ʹ34ʺ N, 78°37ʹ57ʺ W; 1200 m a.s.l.; 27 Apr. 2002; M Buck leg.; photographed by S. Marshall; DEBU .

Other material

COLOMBIA • 1 ♀; Cordillera Occidental, Monte Socorro; 3800 m a.s.l.; “ Coll. Fassl ”; BMNH .

ECUADOR • 1 ♀; Pichincha, 7 km SE of Nanagalito , trout farm; 1500 m a.s.l.; 27 Oct. 1999; S.A. Marshall leg.; MYCRO451-18 sequenced for CO1; DEBU • 1 ♀; Pichincha, Maquipucuna Biological Reserve ; 00°7ʹ34ʺ N, 78°37ʹ57ʺ W; 1200 m a.s.l.; 26–28 Apr. 2002; S.A. Marshall leg.; MYCRO063-15 sequenced for CO1; DEBU .

Description

LENGTH. 14–15 mm.

COLOUR. Head black to dark brown, except for silvery parafacial, distally yellow palpus, pale lower face and reddish brown patches flanking facial carina; thorax orange except for variable black areas of prothorax, postpronotal lobe and areas above and below postpronotal lobe; fore leg with coxa and basal half of femur pale orange, distal half of femur and tibia black, tarsus white; mid and hind femora orange, except for dark anteromedial patches and dark apex, mid tibia and tarsus brown, hind tarsomeres 1–3 pale. Wing very lightly infuscated, with indistinct clear area anterior to crossvein dm-cu. Abdominal tergites orange, except for dark posterolateral patches on T2 (distinct), T3 and T4 (indistinct), pleuron of female pale on pinned specimens, some specimens with orange pigmentation on dorsal third of segments three–five (indistinct on most specimens); oviscape light orange basally, darker distally.

HEAD. Epicephalon and paracephalon smooth and shiny, lower half of frons dull; frontal vitta posteriorly narrow and extending to back of head as a very narrow groove, broad and broadly tapered anteriorly, not reaching frons margin. Postocellar bristles normally strong, closely spaced and far behind level of inner verticals (postocellars absent on two Ecuadorian specimens and shifted posteriorly on other Ecuadorian specimen). Frons separated from antennal socket, antennae separated by width of antennal socket, upper face weakly carinate; lower face flat and microtrichose. Clypeus angled anteriorly, meeting face at an angle of about 100°, shiny medially, laterally microtrichose. Postocciput with sparse small setulae.

THORAX. Cervical sclerite small, unmodified, entirely microtrichose. Postpronotal lobe microtrichose with some scattered small setulae, anterior margin forming a vertical, shiny face.

ABDOMEN. Abdominal segment 1 petiolate; length of 1+2 double that of tergite 3.

FEMALE ABDOMEN. Bursa broad and rugose; ventral receptacle with a distinct, parallel-sided apical part; spermatheca with a long, striate common duct before splitting into ducts leading to paired and single spermathecae. Paired spermathecae large and elongate, each on a separate narrow duct with a large ovate swelling just beyond basal quarter; common duct of paired spermathecae long and indistinctly striate. Single spermatheca small, elongate; duct with a short constricted area at base of spermatheca; duct slightly shorter and narrower than paired duct.

MALE ABDOMEN. Sternites 5 and 6 lightly sclerotized, unmodified. Sternite 7 dark, with a broad anterior apodeme and an expanded, bare, spatulate right apex. Sternite 8 very large, twice as large as epandrium, bare except for setulose posterior quarter. Epandrium small; cercus very small, cercus and posteroventral corner of epandrium setose, anteroventral corner of epandrium forming a broad, parallel-sided lobe articulating with hypandrium. Hypandrium with a very broad, twisted anterior plate with distiphallus apex coiled into its right side. Basal part of distiphallus broadly tubular, gradually expanding to a cuplike apex surrounding a large, two-chambered phallic bulb, upper chamber saddle-like. Ejaculatory apodeme larger than epandrium.

Variation

Two non-type specimens from Ecuador apparently lack postocellar bristles. The presence or absence of postocellar bristles is a relatively constant character in Mesoconius , so this is unusual variation and these specimens would not have been considered to be the same species in the absence of dissections showing every detail of the spermathecal complex to be identical to those of the type. There is also some variation in the extent of pigmentation of the postnotum but, unlike the postocellar bristles, this is normal intraspecific variation.

Remarks

Despite the unusual variation in postocellar bristles, this species is easily recognized by a large number of consistent characters, including general thoracic and head pigmentation, the isolated dark patches on the mid and hind femora, the narrow, pale palpus and the characteristically modified postnotum, with a bare, vertical anterior face. Female internal characters are consistent (Colombian and Ecuadorian specimens, with and without postocellars, were dissected), but only one male specimen is known. Although it is very differently coloured, M. nigricephala sp. nov. shares several synapomorphies with the rest of the M. infestus group, including the two-part ducts of the paired spermathecae, the distally expanded basal phallic section with a hood-like lobe over the phallic bulb, the whip-like phallus incorporated with the broadly twisted anterior hypandrial margin and the very large S8.

Figures

Fig. 26. Mesoconius nigricephala sp. nov. A. Head, ♀ from Colombia. B. Head, specimen from Ecuador (postocellar bristles missing). C. Paratype prior to capture, ♀, Ecuador (inner vertical and postocellar bristles visible). D. Spermatheca and associated structures, specimen from Colombia. E. Male terminalia, lateral view, specimen from Colombia. F. ♀, specimen from Colombia. G. Basal part of phallus. H. Thorax and base of abdomen, ♀, showing prominent katatergite.Abbreviations: bdp = basal distiphallus; ddp = distal distiphallus; pb = phallic bulb.