Diastrophus emeiensis Hu, Nieves-Aldrey, Zhang & Fang sp. nov.

urn:lsid:zoobank.org:act: 5441AB52-9BEF-4194-8614-396E611D941B

(Figs. 2–5)

Type material. HOLOTYPE: F, CHINA: Sichuan, Emeishan, San Dao Gou Road, ex Rubus lambertianus (EM-Morpho-159), 29.594N, 103.379E, 765m a.s.l., gall collected 25.X.2018 (EM-2612), adult emerged 11.IV.2019 (Tube-010780), JL Nieves-Aldrey leg. Emeishan gall expedition 2018, deposited in EBRRS. PARATYPE: 1F, same as holotype, Tube-010779, deposited in EBRRS.

Etymology: Named after the region of Mt. Emei, Sichuan, where the species was collected.

Diagnosis:

Diastrophus emeiensis differs from the other three known East Asian Diastrophus species by the following characteristics:

1) D. wushei: Antennae 14-segmented (13-segmented in D. wushei); F1 as long as F2 (F1 longer than F 2 in D. wushei) (Fig. 3D).

2) D. renai: Head and mesosoma are black (red brown in D. renai) (Figs. 3B,C); hind coxa dark brown (yellow in D. renai) (Figs. 3, 4B); parapsidal line present (absent in D. renai) (Fig. 3A); posterior margin of mesoscutellar fovea indistinct (distinct in D. renai) (Fig. 5A).

3) D. japonicus: Rs straight (slightly curved in D. japonicus) (Fig. 5C); F1 as long as F2 (F1 longer than F 2 in D. japonicus) (Fig. 3D); ratio of POL: OOL: LOL = 2.5: 2.8: 1 (3:5: 2 in D. japonicus) (Fig. 3B); pronotum smooth to coriaceous, sparsely setose (pubescent, strigate in D. japonicus); parapsidal lines apparent (rudimentary in D. japonicus) (Fig. 3A); galls are located asymmetrically to one side of the stem and leaf petiole (integral stem swelling for galls of D. japonicus) (Fig.1 A–C).

It also differs from the eastern Palearctic species Diastrophus rubi (Bouché): Antennae 14-segmented (13- segmented in D. rubi); F1 as long as F2 (F1 1.3× F 2 in D. rubi) (Fig. 3D); Mesoscutellar foveae posterior margins indistinct (well-delimited in D. rubi) (Fig. 5A); head is 2.7× as broad as long (2.1–2.2× in D. rubi); scutellum is 1.3× as long as wide (rounded to wider than long in D. rubi); and galls are located asymmetrically to one side of the stem and leaf petiole (integral stem swelling for galls of D. rubi) (Fig.1 A–C).

Description. Female. Body length 2.5 mm (n = 2).

Coloration. Antennae dark brown. Head black and mesosoma black; tegula brown. Metasoma dark brown (Fig. 2–4). Wings hyaline, infuscated in large areas around R1, 2r, Cu1 (Fig. 5C). All coxae, femora and tarsal claws are dark brown; tibiae and tarsi slightly lighter (Fig. 2).

Antennae. 0.75× as long as body; 14-segmented. F1 as long as F2 (Fig. 3D). Placodeal sensilla present on F2–F12.

Head. In dorsal view 2.7× as broad as long; in anterior view 1.4× as tall as wide; equal to mesosoma in dorsal view. Ratio of POL: OOL: LOL = 2.5: 2.8: 1 (Fig. 3B). Compound eye height to malar space ratio 2×; Frontal face with radiating striae, reaching toruli. Gena moderately expanded behind the compound eye. Face with sparse short setae (Fig. 3C). Toruli situated at mid-height of compound eye. Supraclypeal area raised, narrowing ventrally, with coriaceous sculpture, setose. Clypeus rectangular, 2× as long as wide, with trapezoidal raised area; ventral margin strongly projecting over mandibles. Gena in frontal view curved throughout, coriaceous. Vertex and upper face smooth with setiferous punctures (Fig. 3B). Upper occiput smooth.

Mesosoma. Pronotum smooth to coriaceous, sparsely setose. Pronotal plate rugose, with scattered setae (Fig. 3A). Mesoscutum 0.8× as long as wide in dorsal view; mostly glabrous and smooth, with sparse setose on the lateral lobes. Parapsidal lines apparent. Anterior parallel lines indistinct. Medial mesoscutal impression present as a notch. Notauli complete (Fig. 3A). Scutellum rounded, 1.3× as long as wide in dorsal view. Mesoscutellar disc rugose; with short setae. Circumscutellar carina absent. Mesoscutellar foveae elliptical, with posterior margins somewhat indistinct, medially separated by a wide, weak carina; base of foveae coriaceous (Fig. 5A). Dorsal axilla smooth. Mesopleuron mostly smooth, with striate to rugulose sculpture on the anterior edge (Fig. 4A). Lateral propodeal area with dense setae. Medial propodeal area delimited by carinae, with vertical rugae (Fig. 5B). Nucha with irregular, longitudinal sulci.

Fore Wing. 1.2× as long as body. Radial cell open, 3.3× as long as wide. Veins R1 and Rs not reaching wing margin. Rs straight. Rs+M not reaching M anteriorly. Areolet present. Apical margin of wing with a fringe of setae. Basal cell with scattered setae (Fig. 5C).

Legs. Tarsal claw strongly lobed, measuring 1/2 of length of apical tooth. Hind coxa setose along the posterior edge, and with one row of setae laterally (Fig. 4B).

Metasoma. Shorter than combined length of head and mesosoma. Gt 2 with a single row of setae laterally, glabrous dorsally; Gt 7 with sparse setae. Hypopygial spine short, not extending beyond the hypopygium, with setae along its entire length (Fig. 4B).

Males. Unknown.

Distribution. Mt. Emei, Sichuan, China.

Biology. The new species induces a multilocular stem and petiole gall on Rubus lambertianus (Figs. 1A–C). The gall is located asymmetrically to one side of the stem and leaf petiole, rather than being integral to these structures, and its development often causes death of the associated leaf. The gall is irregularly sausage-shaped, usually with a rounded base distinct from the stem, and tapering into an affected petiole. The gall is green (sometimes with reddish tints) like the stem, and is smooth and shiny. Each gall extends along the stem and petiole for c. 70mm, with a maximum width of 8 mm. Dissection revealed an internal structure showing two types of larval chambers and larvae: the Diastrophus gall inducer larval chamber is regularly ovoid and its internal wall is covered by a fine membranous envelope (Fig. 1D). The second type of larval chambers has a less regular form which lacks the membranous lining. They are occupied by larvae that show stronger mandibles (three teeth) than Diastrophus, which probably represent an undescribed inquiline Synophromorpha Ashmead, 1903 species (Figs. 1E, F).

Variation. The depression on the anterior edge of mesopleuron is less prominent on the paratype.

Molecular Data. The COI fragment of D. emeiensis was 313 bp in length after trimming, and is deposited in GenBank with accession number PV828417. The K3Pu+F+G4 model was used to construct the phylogeny in Fig. 6 after it was identified as the best fit to the data by Modelfinder. Diastrophus was recovered as monophyletic and sister to Xestophanes, and D. emeiensis was recovered as a distinct lineage that is sister to the rest of Diastrophus, which includes D. mayri, D. potentillae Bassett, 1864, D. rubi, and D. turgidus Bassett, 1870 (Fig. 6). The pairwise distance of D. emeiensis from other Diastrophus species is 8.7–12.2% (Table 2).