Colocasiomyia daiae Xue & Gao, 2022

Xue, Xian-Ci, Jiao, Run-Jie, Yu, Li & Gao, Jian-Jun, 2022, A new species of the Colocasiomyia gigantea species group (Diptera, Drosophilidae) breeding on inflorescences of Scindapsus maclurei (Araceae), Zootaxa 5120 (4), pp. 586-594 : 589-593

publication ID	https://doi.org/ 10.11646/zootaxa.5120.4.8
publication LSID	lsid:zoobank.org:pub:7178EBD2-91FE-4E82-94AC-500223E92040
DOI	https://doi.org/10.5281/zenodo.6392959
persistent identifier	https://treatment.plazi.org/id/147887C7-FFC9-FF93-FF16-FC63FEF90C94
treatment provided by	Plazi
scientific name	Colocasiomyia daiae Xue & Gao
status	sp. nov.

Treatment

Colocasiomyia daiae Xue & Gao View in CoL , sp. nov.

( Figs 3-5 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Diagnosis. The new species can be discriminated from the known members in the gigantea group by the following characters: (a) prementum ventrally continuously convex in lateral view ( Fig. 3F View FIGURE 3 ; flat in the known species); (b) dorsocentral setae three pairs ( Fig. 3A View FIGURE 3 ; two pairs in known species); (c) costa with extraordinarily long and thick setae sparsely ( Fig. 3I View FIGURE 3 ; lacking such long setae in the known species), (d) male abdominal sternite VI absent ( Fig. 3L View FIGURE 3 ; present in the known species); and (e) lateral lobes of oviscapt fused with each other dorsosubapically (fused with each other only apically in known species), lacking any warts on basal half ( Fig. 4F View FIGURE 4 ; with large patch of warts in known species).

Description (♂, ♀). Head ( Fig. 3 View FIGURE 3 A−H): Supracervical setae 7−9 per side; dorsomedial arm of tentorial apodeme about 1/3 as long as dorsolateral arm. Eye red, somewhat roundish, with sparse, fine interfacetal setulae nearly as long as the diameter of a facet. Frontal vitta mat, black. First flagellomere not concave on inner margin. Facial carina trapeziform, medially about 1.5 times as wide as first flagellomere, as long as pedicel and first flagellomere combined. Cibarium with 4 anterior sensilla, medial sensilla (minute, 3 or 4 per side) longer than posterior ones (minute, 1 per side); sensilla campaniformia 2 per side; Prementum ventrally continuously convex, with 3−4 (2 medial, 1−2 lateral) pairs of setea. Labellum with 15 pseudotracheae per side.

Thorax ( Fig. 3A, B View FIGURE 3 ): Scutum, scutellum and thoracic pleura glossy, blackish brown to black. Acrostichal setulae in 6 rows. Additional pair of dorsocentral setae present on presutural area.

Wing ( Fig. 3I View FIGURE 3 ) hyaline, veins yellow. Halter grayish brown except for small grayish white patch on apical portion of knob.

Legs ( Fig. 3A, J View FIGURE 3 ) blackish brown to black except for grayish yellow tarsi. Foreleg second tarsomere with three pairs of blade-like pegs: the upper two pairs vertically, and the third pair somewhat horizontally arranged. Foreleg coxa large, with 1−2 long setae on underside near attachment to trochanter. Preapical dorsal seta absent on all legs.

Abdomen ( Fig. 3A, K–M View FIGURE 3 ): Tergites glossy, entirely black; II to VI+VII each bearing setulae and setae in approximately 3−5 transverse rows; setae of posteriomost row largest, very long. Sternites grayish brown to blackish brown. Caudomedial margin of female sternite VII slightly notched.

Male terminalia ( Fig. 4A–E View FIGURE 4 ): Epandrium pubescent except for anterior and ventral portions ( Fig. 4A View FIGURE 4 ), with somewhat narrow phragma on anteromedial margin ( Fig. 4B View FIGURE 4 ); anteroventral portion of epandrium curved inward, apically articulated to lateral corner of hypandrium. Cercus somewhat semilunar, not projected at ventral apex, pubescent except for anterior margin and ventral 1/2, with ca. 30 setae ( Fig. 4A View FIGURE 4 ). Surstylus well developed, with three large, black, peg-like teeth on distal margin; lowest tooth distinctly long, distally flat and slightly curved inwards ( Fig. 4A View FIGURE 4 ). Subepandrial sclerite moderately sclerotized, appearing as a long, arched structure (not shown). Hypandrium long and thin plate, constricted subdistally, posteriorly T-shaped, median gonocoxite connecting to dorsobasal corners of phallus through somewhat membranous, ribbon-like, lateral gonocoxites ( Fig. 4C View FIGURE 4 ). Pregonite broad, blade shaped, distally somewhat obliquely truncated, coalescent to hypandrium, apically curved ventrad, with a cluster of ca. 5 fine sensilla ( Fig. 4C,E View FIGURE 4 ). Phallal sheath separated into a pair of lobes connected with each other ventrally, pubescent around dorsomedial portion, arcuate in lateral view, dorsoapically prolongated, somewhat pointed apically and bent ventrad, like proboscis, ventrosubapically notched in lateral view ( Fig. 4D View FIGURE 4 ).

Female terminalia ( Fig. 4F View FIGURE 4 ): Tergite VII mid-dorsally not constricted; VIII pubescence dorsoposteriorly only, with 2 setae somewhat transversally arranged on discolored, posteromedial portion of the tergite. Epiproct and hypoproct entirely pubescent. Oviscapt consisting of a pair of sclerotized, blackish brown lobes. Lobes lack warts, fused with each other dorsosubapically, densely wrinkled on ventral portion, invaginated to form an inner ridge (arcuate in lateral view); distal portion about 2/ 3 in maximum as wide as proximal portion, slightly bent ventrad, concaved at distal apex, obliquely truncated caudoventrally. Each lobe bearing ca. 22 trichoid ovisensilla: three thin, short ones on dorsal, subapical margin, ca. seven longer, thicker ones around the apex above the apical concave, and ca. 12 thin, moderate ones on the caudoventral portion below the concave.

Measurements: BL (body length) = 2.50 in holotype (range in 5♂ paratypes: 2.10−2.60; range in 5♀ paratypes: 2.39−2.91) mm, ThL (thorax length) = 1.02 (0.90−1.07; 0.86−1.24) mm, WL (wing length) = 1.85 (1.75−2.00; 1.65−2.00) mm, WW (wing width) = 0.80 (0.75−0.85; 0.70−0.96) mm.

Indices: FW/HW (frontal width/head width) = 0.55 (5♂, 5♀, or less if noted, paratypes: 0.51−0.56), ch/o (maximum width of gena/maximum diameter of eye) = 0.45 (0.48−0.56), prorb (proclinate orbital seta/posterior reclinate orbital seta in length) = 0.88 (0.70−0.83), rcorb (anterior reclinate orbital seta/posterior reclinate orbital seta in length) = 0.41 (0.28−0.43), orbito (distance between proclinate and posterior reclinate orbital setae/distance between inner vertical and posterior reclinate orbital setae) = 0.59 (0.46−0.69), vb (subvibrissal seta/vibrissa in length) = 0.55 (4♂, 5♀: 0.40−0.62), dcl (anterior dorsocentral seta/posterior dorsocentral seta in length) = 0.73 (0.61−0.71), dcl-2 (4♂, 5♀: additional dorsocentral seta/posterior dorsocentral seta in length) = 0.56 (0.58−0.65), dcp (distance between ipsilateral dorsocentral setae/distance between anterior dorsocentral setae) = 0.84 (0.78−0.89), sterno (anterior katepisternal seta/posterior katepisternal seta in length) = 0.80 (0.55−0.65), sterno-2 (mid katepisternal seta/posterior katepisternal seta in length) = 0.37 (0.27−0.34), sctl (basal scutellar seta/apical scutellar seta in length) = 0.97 (4♂, 5♀: 0.84−1.04), sctlp (distance between ipsilateral scutellar setae/distance between apical scutellar setae) = 1.42 (1.17−1.92), C (second costal section between subcostal break and R 2 +3/third costal section between R 2 +3 and R 4 +5) = 1.40 (1.21−1.52), 4c (third costal section between R 2 +3 and R 4 +5/M 1 between r-m and dm-m) = 1.81 (1.68−2.28), 4v (M 1 between dm-m and wing margin/M 1 between r-m and dm-m) = 2.55 (2.34−3.13), 5x (M 4 between dm-m and wing margin/dm-m between M 1 and M 4) = 1.44 (1.23−1.75), ac (3rd costal section between R 2 +3 and R 4 +5/distance between distal ends of R 4 +5 and M 1) = 4.05 (3.50−4.39), M (M 4 between dm-m and wing margin/ M 1 between r-m and dm-m) = 0.67 (0.61−0.98), C3F [length of heavy setation in third costal section/(length of heavy setation in third costal section + length of light setation in third costal section)] = 0.96 (0.92−0.99) .

Pre-imaginal stages ( Fig. 5A–K View FIGURE 5 ): Eggs ( Fig. 5A View FIGURE 5 ) all laid deep into slits between pistils, 0.97 ± 0.03 (mean ± stand deviation, n = 10) mm in length excepting two long filaments. Each segment of larva ( Fig. 5B–D View FIGURE 5 ) with one to five transverse rows of fine spicules on dorsal surface and approximately five rows of spicules on ventral surface. Caudal two segments of puparium ( Fig. 5E View FIGURE 5 ) elongate, without spicules; second last one distally blackish, last one somewhat whitish. Posterior spiracles short, yellowish brown. Anterior spiracle of puparium with approximately 14 long branches in whorl; stalk longer than branches; stalk distally and branches basally blackish. Cephalopharyngeal skeleton ( Fig. 5 View FIGURE 5 F−H): ventral margin of mouth hook lacking teeth in first instar ( Fig. 5I View FIGURE 5 ) but with irregular dentation in second and third instars ( Fig. 5J, 5K View FIGURE 5 ); latticed process of pharyngeal sclerite fused to dorsal wing in all instars; vertical bridge width approximately 1/3 of dorsal wing length in all instars ( Fig. 5 View FIGURE 5 F−H).

Holotype. ♂ (#10564): CHINA: ex inflorescences of Scindapsus maclurei (Merr.) Merr. et Metc., Zahan Station, Wuzhishan National Nature Preserve, Qiongzhong , Hainan, China , N18°53', E109°45', ca. 540 m a.s.l., 30.vi.2021, R-J Jiao ( KIZ). GoogleMaps

Paratypes. 20♂ (#10565–568, #10574–589), 21♀ (#10569–573, #10590–605), same data as holotype ( KIZ) GoogleMaps .

Distribution. China (Hainan).

Host plants. Scindapsus maclurei (Merr.) Merr. et Metc ( Fig. 1 View FIGURE 1 ).

Etymology. In honor of the late professor Zhuo-Hua Dai, a geneticist at the Peking University who worked with drosophilid flies over the past decades.

Remarks. All adult flies having emerged from S. maclurei inflorescences collected in Hainan were of C. daiae sp. nov., suggesting that this fly species breeds monopolistically on this host plant. There are numbers of morphological features supporting the assignment of this Colocasiomyia species to the gigantea group. An important character is a pair of long filaments (dorsal appendages, DAs) of egg, which are seen across the species of the gigantea group but absent in the other species groups of Colocasiomyia . This character is considered to have evolutionarily been gained in the gigantea group as an adaptation to seemingly oxygen-poor condition of particular oviposition sites, i.e. very narrow slits between pistils on the spadix: respiratory exchange should be improved through the long DAs for embryos and 1st instar larvae long staying within egg capsule under such conditions ( Fartyal et al. 2013, Li et al. 2014). Within the gigantea group, the new species is related to C. hailini Li & Gao, 2014 and C. yini Li & Gao, 2014 in sharing the surstylus equipped with three (upper two short, lowest one distinctly elangated) stout prensisetae ( Li et al. 2014).