Pseudogaurax striatus Ismay & Ang, 2019

Ismay, Barbara & Ang, Yuchen, 2019, First records of Pseudogaurax Malloch 1915 (Diptera: Chloropidae) from Singapore, with the description of two new species discovered with NGS barcodes, Raffles Bulletin of Zoology 67, pp. 412-420 : 415-418

Pseudogaurax striatus Ismay & Ang , new species

( Fig. 2 )

Type Material. Holotype (here designated), female: SINGAPORE, Pulau Ubin Mangrove Forest , from Malaise Trap PU3 [1°25′16.536″N 103°56′54.095″E] (Collection event: 29243, 17-25.xi.2011). Specimen code ZRC _ BDP0021667 , deposited in the LKCNHM ( ZRC). Cytochrome oxidase I ( COI) partial-cds for this specimen deposited in GenBank under reference MK 541946 .

Diagnosis. Almost entirely yellow species with a black inverted ‘U’-shaped marking on the scutum, a black lateral stripe on the pleura and yellow legs except for black markings on the middle and posterior tibia.

Description. Length. Body 2.3 mm, wing 1.44 mm.

Head ( Fig. 1A, B ). Broader than deep (ocelli to proboscis) and as long (occiput to antennal sockets) as deep (0.47: 0.38: 0.38 mm), entirely pale yellow except for black ocellar tubercle (this is the raised part of the ocellar triangle around the ocelli), black dorsal margin of postpedicel, black arista, black posterior and ventral eye margins and two black marks on occiput, dorsal to insertion of neck. Head and thoracic setae yellow. Five orbital setae developed, long, slightly incurved and reclinate equal to length of ocellar setae, increasing in size posteriorly, the most posterior approximately equal in length to width of posterior margin of ocellar tubercle. Outer vertical seta strongly developed, slightly longer than half maximum width of frons, lateroclinate and reclinate; inner vertical seta, incurved and slightly proclinate, about 0.75 times length of outer vertical seta, postocellar setae strongly developed, long, cruciate and reclinate, 0.8 length of outer vertical seta, ocellar setae upright and cruciate, 0.75 length of postocellar setae. Frons slightly longer than broad (0.31: 0.25 mm), width measured at level of anterior ocellus, lateral margins of frons parallel, anterior margin slightly convex, pale yellow, dusted, with several longer setulae present outside of ocellar triangle, the anterior of these setulae incurved. Ocellar triangle bare, large, shiny, very pale yellow, almost white, extending almost to anterior margin of frons by pointed tip, gap equal to width of one ocellus, lateral margins slightly convex, posteriorly almost reaching eye margin, gap equal to width of one ocellus. Eye oval, long axis oblique with short, dense pubescence, ommatidia in anterior half enlarged. Face approximately 1.5 times as deep as wide, pale yellow, dusted, flat, carina absent; antennae pale yellow except for black mark on dorsal margin of postpedicel (about as large as two ocelli), postpedicel reniform, twice as deep as long, black around insertion of arista; arista laterodorsal, black, with fine, short pubescence (equal in length to diameter of arista), 2.5 times as long as length of postpedicel, long apical seta on pedicel; gena narrow, as deep as length of postpedicel, pale yellow, dusted, one row of pale setulae on ventral margin, two setulae dorsal to obtuse vibrissal angle, one setula each longer at anterior and posterior margin; occiput pale yellow except for black eye margin and two black reniform marks above insertion of neck and slightly smaller than postpedicel; proboscis pale yellow, almost white, short, weakly sclerotised; palpus pale yellow, almost white, as long as postocellar seta, with two apical long, pale setulae; mouth edge slightly protruding; clypeus dusted pale yellow, almost white.

Thorax ( Fig. 1A, B ). Scutum longer than wide (0.53: 0.41 mm), yellow, darker orange yellow on central stripe, the latter occupying entire space between dorsocentral lines, this stripe pale yellow in posterior third, stripe laterally and anteriorly bordered by black lines forming an inverted ‘U’, the lines as thick as postpedicel is wide, the area lateral to lines equally wide as lines, this area presuturally almost white including postpronotal lobe, the latter with one strong, dark, reclinate, posterior seta, as long as inner vertical seta, postsutural area yellow, suture covered by dark stripe as wide as anterior tarsi; scutum only slightly convex and shiny, but central and lateral stripes covered in numerous, pale, long setulae, as long as inner vertical seta, these setulae form a bi-serial convergent line along the centre almost giving the appearance of acrostichals, one yellow posterior dorsocentral seta developed, 1.5 times as long as outer vertical seta, no acrostichal setae developed; yellow notopleuron with 1 plus 1 yellow setae, each as long as outer vertical seta; dark yellow posterior post-alar seta, as long as outer vertical seta. Pleura entirely shiny, pale yellow, almost white, except for small black mark around white anterior spiracle, joining black stripe along ventral margin of anepisternum and ending at suture, as thick as anterior tibia, ventral third of katepisternum yellow, not as pale as remaining pleura, with a strong pale yellow seta at posterior dorsal margin, directed anteriorly, as long as inner vertical seta. Dorsal half of katatergite and anatergite covered in dark brown mark, dorsal half of postnotum almost white, ventral half covered by black stripe, the latter is reduced to a thin line in the middle third by a ventral yellow mark, entire postnotum shiny. Scutellum pale yellow, shiny, broader than long (0.25: 0.16 mm), shield-shaped with sparse yellow setulae on flat disc, lateral margins bare; cruciate apical yellow scutellar setae not approximated, separated by 1.5 times the width of ocellar tubercle, 1.5 times as long as scutellum, arising from small tubercles, one pair of short yellow lateral scutellar setae, one third as long as apicals, separated from apical scutellars by half the distance between apical scutellars. Haltere pale yellow, almost white.

Wing ( Fig. 1A, B ). Translucent, covered in microtrichia, with thin, pale brown veins, cross-veins almost translucent, R 1 slightly thicker, Costa ending where M 1 joins margin, slightly beyond apex of wing, covered with setulae that are longest along apical half of R 1 and R 2+3; costal ratios measured from base of basicosta to point where R 1 touches costa, then along costal margin of R 2+3, then along costal margin of R 4+5: 0.56: 0.47: 0.38: 0.16 mm; cell r 1 broader than cell r 2+3 at point where R 1 meets Costa, cells br and bm+m unusually narrow, veins R 4+5 and M 1 parallel up to costal wing margin, distinct kink in M 4, costal break basal to where R 1 touches Costa, basicosta white.

Legs ( Fig. 1B ). All legs mainly pale yellow, shiny, middle and posterior tibia black except for apical and basal one eighths; apical two thirds of all femora pale yellow, basal third paler, almost white; all setulae pale, several pale setae ventrally to anterior femur, as long as femur is deep; posterior femora and tibiae twice as wide as others; left apical four tarsal segments stuck on top of right tarsus; apical tarsal segment scarcely wider than basal segment; posterior tibial organ well developed, oval, silvery, in middle of black mark, as long as one eighths of tibia, as wide as one third of tibia, about three times as long as wide; femoral organ absent; long, pale, thin, anteroventral spur on mid tibia, as long as tibia is deep.

Abdomen ( Fig. 1A, B ). Ventrally pale yellow, three fifths of tergite 1+2 pale yellow, almost white in middle, lateral one fifths dark brown, remaining tergites dark brown dorsally and laterally except for anterior margin that is pale yellow; setulae pale.

Female terminalia ( Fig. 1A, B ). Tergite 6 dark brown, 1.5 times as wide as tergite 7, tergite 6 slightly wider than long, separated from tergite 7 by white membrane, tergite 7 twice as long as wide, separated from tergite 8 by white membrane, cerci twice as long as wide, black with two long apical setulae.

Barcode. Cytochrome oxidase I (COI) partial-cds (313 b.p.; GenBank accession code MK541946 ) as follows:

---cctatcttcaattattgcccatggaggagcttcagttgatttagcaattttttcact tcatctagctggagtttcatcaatcttaggagcagtaaattttattactactgtaattaa tatacgttcaactggaattacatttgatcgaatacctttatttgtttgatcagtagtaat tacagctttattattattgctttcattaccagttttagcaggagctattacaatattatt aacagatcgaaatttaaatacatcattctttgacccagcaggtgggggagaccca attctttatcaacatttattc

Etymology. The species name striatus (striped) is derived from Latin, referring to the stripe at the ventral margin of the anepisternum.

Remarks. This new species runs to couplet 7 in the key by Ismay (1987), but then does not fit the description for Pseudogaurax chiyokoae Kanmiya, 1972 as the scutal markings of P. striatus , new species are different. It also runs to couplet 6 in the key by Cherian (2013), but again does not fit the description for P. sabroskyi Cherian, 1989 in that the ocellar triangle in this new species does not reach the anterior margin and the anterior legs are entirely yellow.

Figures

Fig. 2. Habitus of holotype of Pseudogaurax striatus, new species (female, specimen ZRC_BDP0021667). A, lateral habitus showing thoracic pleura, head, legs and wing, note the stripe at the bottom margin of the anepisternum; B, dorsal habitus. Note extended terminalia on both A and B.

Fig. 1. Habitus of holotype of Pseudogaurax sexnotatus, new species (female, specimen ZRC_BDP0025357). A, dorsal habitus showing dorsal scutum and scutellum, as well as head capsule in oblique view, note the six distinct spots on thorax; B, lateral habitus showing thoracic pleura, head, legs and wing, as well as terminalia behind wing; C, dorsal view of head.