Colocasiomyia daiae Xue & Jiao & Yu & Gao 2022, sp. nov.
Creators: name: Xue, Xian-Ci
name: Jiao, Run-Jie
name: Yu, Li
name: Gao, Jian-Jun
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Drosophilidae
Colocasiomyia
Colocasiomyia daiae

description: Colocasiomyia daiae Xue & Gao, sp. nov.
(Figs 3-5)
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; flat in the known species); (b) dorsocentral setae three pairs (Fig. 3A; two pairs in known species); (c) costa with extraordinarily long and thick setae sparsely (Fig. 3I; lacking such long setae in the known species), (d) male abdominal sternite VI absent (Fig. 3L; 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; with large patch of warts in known species).
Description (♂, ♀). Head (Fig. 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): 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) hyaline, veins yellow. Halter grayish brown except for small grayish white patch on apical portion of knob.
Legs (Fig. 3A, J) 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): 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): Epandrium pubescent except for anterior and ventral portions (Fig. 4A), with somewhat narrow phragma on anteromedial margin (Fig. 4B); 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). 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). 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). 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). 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).
Female terminalia (Fig. 4F): 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): Eggs (Fig. 5A) 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) 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) 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 F−H): ventral margin of mouth hook lacking teeth in first instar (Fig. 5I) but with irregular dentation in second and third instars (Fig. 5J, 5K); 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 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).
Paratypes. 20♂ (#10565–568, #10574–589), 21♀ (#10569–573, #10590–605), same data as holotype (KIZ).
Distribution. China (Hainan).
Host plants. Scindapsus maclurei (Merr.) Merr. et Metc (Fig. 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).
description: Published as part of 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), pp. 586-594 in Zootaxa 5120 (4) on pages 589-593, DOI: 10.11646/zootaxa.5120.4.8, http://zenodo.org/record/6392957