Perochaeta cuirassa Ang 2010

Ang, Yuchen & Meier, Rudolf, 2010, Five additions to the list of Sepsidae Diptera for Vietnam: Perochaeta cuirassa sp. n., Perochaeta lobo sp. n., Sepsis spura sp. n., Sepsis sepsi Ozerov, 2003 and Sepsis monostigma Thompson, 1869, ZooKeys 70, pp. 41-56 : 43-46

Perochaeta cuirassa Ang 2010 sp. n. Figs 1-5

Material.

Holotype. ♂ (RMBR), Vietnam, Lào Cai Province, Sa Pa Valley. Baited with cow dung at forest edge next to a small cascade alongside highway, ca. 850m along the road westward of the Thác bạc (Silver Waterfall) tourist attraction [22°23'23.90"N; 103°44'50.32"E, elevation 2600m above sea level, ASL]. Collected 16.VII.2010 (Ang Y). Paratypes. 2 ♂ (RMBR), collected from same locality and time as holotype.

Etymology.

The specific epithet refers to the shape of the main scleral plate for the 4th sternite, which resembles a cuirass or breastplate armor.

Diagnosis.

Adult male Perochaeta cuirassa is very similar to Perochaeta lobo and can only be reliably distinguished from the latter based on the 4th sternite [cf. Perochaeta cuirassa (Fig. 1) and Sepsis lobo (Fig. 6)]: The sternite in Perochaeta cuirassa lacks distinct lobes on the posterior end of the 4th sternite, while the sternite brush is thick and squat (as opposed to long and thin in Perochaeta lobo ), and the main scleral plate is much broader (long as wide) than in Perochaeta lobo (twice long as wide). The hypopygium [cf. Perochaeta cuirassa (Figs 2-4) and Perochaeta lobo (Figs 7-9)] is also distinct, with Perochaeta cuirassa bearing a large median, decussating protrusion on the dorsal side of the surstylus, while Perochaeta lobo has a sub-median protrusion on the ventral side of the surstylus. Perochaeta cuirassa is also readily distinguished from all other Perochaeta species based on the morphology of the 4th sternite and hypopygium: The sternites brush of Perochaeta cuirassa (Fig. 1) has significantly more bristles (>40 per brush) than either Perochaeta hennigi Ozerov, 1992 (Fig. 10) or Perochaeta dikowi (Fig. 12), both of which have only 5-6 large bristles in addition to a few weaker bristles. Perochaeta cuirassa also has strong bristles lining the distal margin of the sternite, which are not found in Perochaeta dikowi or Perochaeta hennigi . The surstylus of Perochaeta cuirassa (Fig. 2) resembles that of Perochaeta hennigi (Fig. 11), but can be distinguished by the large median surstylus projection, which is long and curved in Perochaeta cuirassa but short and broadly triangular in Perochaeta hennigi . Both Perochaeta dikowi (Fig. 13) and Perochaeta orientalis (De Meijere, 1913) (Fig. 14) lack large median projections. Perochaeta cuirassa can further be distinguished by the radial-medial cross-vein dividing the discal-medial cell which is in a ratio of 3: 1 in Perochaeta cuirassa , 2.5: 1 in Perochaeta dikowi , 2: 1 in Perochaeta hennigi and 1: 1 in Perochaeta orientalis .

Description (male).

Colour. Head capsule mostly black except for thin yellow strip along subgena and parafacial area. Lunule, facial carina and antennae light brown; antennal groove dark brown. Proboscis brown. Thorax, scutellum and abdomen wholly black. Legs largely yellow except for the following: basal regions of fore coxa brown, mid and rear femora with a dark half-ring subapically (edges of which are diffuse on the apical edge), basal half of mid and rear tibiae dark brown. All tarsi with tarsomeres 3-5 brown; tarsomeres 1-2 yellow with brown region apically. Wing clear except for basicostal cell and basal third of costal cell, which is brown. Veins dark brown. Calypter creamy, margin and fringe-hairs yellowish. Haltere milky yellow with brown base.

Head. Roundish, facial carina short and shallow, facial area receding. Gena and parafacial region narrow. Ocellar prominence and occipital region lightly microtomentose. Chaetotaxy: 1 ocellar, 1 divergent postocellar, 1 outer vertical; inner vertical absent. Orbital very reduced to absent. 2 vibrissae. 3-4 postocular. Lower fascial margin lined with setulae.

Thorax. Scutum, postpronotum, scutellum and subscutellum wholly microtomentose. Mediotergite microtomentose but glossy in the medial region. Scutellum twice wide as long. Pleural pruinosity pattern (Fig. 5): Proepisternum glossy with ventral region microtomentose. Anepisternum largely glossy with anterioventral region densely microtomentose. Katepisternum largely with dense tomentosity except for glossy anterioventral region. Anterior side of anepimeron glossy while posterior side lightly microtomentose and posterioventral region densely microtomentose. Postpronotum, katatergite, meron and metepimeron lightly-dusted. Chaetotaxy: 1 apical scutellar, 1 reduced, setulae-like basal scutellar, 1 dorsocentral, 1 postalar, 1 supraalar, 2 notopleural, 1 postpronotal, 1 anepisternal and 1 posterior spiracular. Postpronotoum, prescutum and anepisternum with few, sporadic setulae.

Legs. Forelegs unmodified in males; all femora and tibiae without posteriodorsalor anteriodorsal setae. Mid tibia with row of short setae on anterior apex. Rear tibia with barely-visible osomoterial patch on medial posteriodorsal side. Rear basitarsus with three ventral dark spines basally.

Wings. Without pterostigma. Veins bare. Covered with microtrichiae except for costal, subcostal, basal-medial and posterior-cubital cells, as well as base of cells r1 and r2+3. Microtrichiae sparse on basal region of basal-radial and discal-medial cells. Radial-medial cross-vein divides discal-medial cell by ratio of 3: 1. Length: 4.6-4.9 mm.

Abdomen. Glossy black; syntergite 1+2 - tergite 5 normal, tergite 6 missing, syntergite 7+8 present and extending ventrad as a narrow sclerite. Spiracles 1-4 on intersegmental membrane, spiracle 5 on ventral margin of tergite 5, spiracle 7 and 8 adjacent on margin of syntergite 7+8. Sternite 1 broadly rectangular while sternite 2 is triangular, tapering posteriorly; sternite 3 is oblong. 4th sternite heavily modified (Fig. 1); greatly expanded, long as is wide, and in the shape of a breastplate. Two stout moveable appendages (= sternite brushes) branch off laterally; each appendage resembles a painter’s brush, with large, thick bristles on the outer side and shorter, thinner bristles on the inner side.Posterior edge of 4th sternite invaginated with strong setae lining the outer discal margin as well as submedially. A Y-shaped apodeme extends underneath and anterior to the 4th sternite.

Hypopygium (Figs 2-4). Cercal plate with two very weak lobes; distal margin of each lobe covered with numerous setae. Hypopygium triangular with a two tooth-like projections on the inner side basal to where the surstylus branches off (Fig. 4). Surstylus itself fused to hypopygium, angled dorsally, and branches off subterminally (Fig. 3). Each surstylus has a large hook-like median projection that curves dorsally and decussates. Terminal section of surstylus shaped like a scapula, with cuticular “teeth” and setulae on distal margin, and a small inward-facing “tooth” on both the ventral and dorsal region subterminally pointing towards the median.

Distribution.

Vietnam ( Lào Cai).