Microtendipes shoukomaki Sasa, 1989

Niitsuma, Hiromi, 2017, Review of the Japanese Microtendipes tera: Chironomidae: Chironominae), with description of a new species, Zootaxa 4320 (3), pp. 535-553 : 541-544

Microtendipes shoukomaki Sasa

( Figures 2 , 5B )

Microtendipes britteni [nec Edwards, 1929: 399]: Sasa 1980: 29; Qi & Wang, 2006: 40 . Microtendipes shoukomaki Sasa, 1989a: 29 .

Microtendipes ginzanefeus Sasa & Suzuki, 2001: 12 . Syn. nov.

Material examined. Holotype of Microtendipes shoukomaki , M (NSMT-I-Dip 4 649), labelled, “ No. 154: 31”, JAPAN : Toyama, Shou River , 7.ii.1989. Holotype of Microtendipes ginzanefeus , M ( NSMT), labelled, “No. 403: 51”, JAPAN : Hokkaido, Mt. Ginzan , 2.ix.2000. Non-types. M, F ( SUM), JAPAN : Mie, Takicho , small stream, 23.vii.1981; Le / Pe /M, 2 Pe /M, 8 Pe /F, F, 3 Pe, Le / Pe, 9 Le, 6 L ( SUM) , Shizuoka, Shimizu, Okitsu River , 3.ii.1985 (emerged 9.ii–5.iii.1985); F ( SUM) , Shizuoka, Shimizu, Yanbara River , 16.vi.1985; M ( SUM), as previous except 29.xi.1986; Pe /M ( SUM) , Shizuoka, Shimizu, Ihara River , 15.x.1989 (emerged 30.x.1989); Pe /M ( SUM) , Shizuoka, Fujinomiya, Inase River , 15.vii.1991 (emerged 28.vii.1991); Pe /M ( SUM) , Fukushima, Iwaki, Obisa River , 16.viii.1991 (emerged 25.viii.1991); Pe /M ( SUM) , Fukushima, Hirono, Asami River , 15.viii.2001 (emerged 21.viii.2001); 6 Le / Pe /M ( EJNU), CHINA : Guangdong, Guangzhou, Zengcheng District, Lan Stream , 30.iv.2017 (emerged 5.vi.2017); Pe /M ( EJNU) , Anhui, Mt. Huang, Fuxi stream, 25.v.2012 (emerged 1.vi.2012); M ( EJNU) , Yunnan, Xishuangbanna, Yiwu County, Guafengzhai , 26.iv.2017.

Description. Male (n = 8). Total length 4.1–4.9, 4.5 mm.

Coloration. Thorax dark brown with 3 scutal vittae shining black. Abdomen green with somewhat darkened segments VI–IX or VII–IX. Wing without any marking. Legs yellow with all knee joints and foretibia dark brown.

Head. Temporals 14–21, 16. AR 2.0–2.1, 2.0. Clypeus with 17–25, 20 setae. Lengths of palpomeres 1–5 (µm): 55–60, 59 (6); 60–70, 65 (6); 275–300, 286 (6); 250–275, 265 (6); 375–460, 409 (6), respectively. Pm4/Pm3 0.91– 0.95, 0.93 (6); Pm5/Pm4 1.5–1.7, 1.5 (6). Pm3 with 2–4, 3 (7) sensilla clavata, longest 15–20, 18 (7) µm long.

Thorax. Lateral antepronotals 4–6, 5; acrostichals absent; dorsocentrals 9–13, 12; prealars 4–5, 4; scutellars 20–30, 23.

Wing. Length 2.8–3.3, 3.0 (6) mm. VR 1.1–1.2, 1.1 (6). Veins R, R1 and R4+5 with 16–24, 21 (6); 15–26, 21 (6); 25–42, 32 (6) setae, respectively. Squama with 15–20, 17 (6) setae.

Legs. Forefemur externally with 2 rows of proximally directed setae. Mid ta1 with 7–14, 10 sensilla chaetica, distalmost located 0.40–0.53, 0.47 from base. Lengths and proportions of leg segments as in Table 2.

Hypopygium ( Figure 2A ). Anal tergite with anterior bands medially separated from each other; median setae absent; anal point tapering toward pointed apex. Superior volsella ( Figures 2B, C ) stout, curved ventrally, pointed apically, with one basal and 2–7, 5 dorsolateral setae. Median volsella absent. Gonostylus 140–180, 155 (5) µm long, 4.0–4.4, 4.3 (5) times as long as broad at middle.

Female (n = 11). Total length 2.8–4.0, 3.6 mm.

Coloration. Similar to male.

Head. Temporals 16–24, 19. Antenna with terminal flagellomere 170–230, 194 µm long, as long as or slightly shorter than preceding 2 flagellomeres together; AR 0.36–0.49, 0.44 (10). Clypeus with 19–28, 22 setae. Lengths of palpomeres 1–5 (µm): 45–60, 57 (10); 55–70, 63 (10); 270–320, 294 (10); 260–335, 290 (10); 355–490, 426 (10), respectively. Pm4/Pm3 0.84–1.1, 0.99 (10); Pm5/Pm4 1.3–1.6, 1.5 (10). Pm3 apically with 4–5, 4 sensilla clavata, longest 18–25, 21 µm long.

Thorax. Lateral antepronotals 3–5, 4; acrostichals absent; dorsocentrals 13–21, 17; prealars 4–5, 4; scutellars 24–32, 28.

Wing. Length 2.6–3.7, 3.4 mm. VR 1.2 (6). Veins R, R1 and R4+5 with 24–31, 28 (9), 26–35, 29 (9) and 50–85, 62 (9) setae, respectively. Squama with 17–23, 20 setae.

Legs. Mid ta1 with 24–37, 28 sensilla chaetica, distalmost located 0.53–0.61, 0.56 from base. Lengths and proportions of leg segments as in Table 2.

fe ti ta1 ta2 ta3 ta4 ta5 LR BR Male P1 1192–1447 1167–1447 1497–1700 736–888 660–787 584–697 254–305 1.2–1.4 2.1–2.7

1269 1266 1621 793 698 614 279 1.3 2.4 P2 1269–1523 1167–1421 736–838 406–482 305–355 178–203 102–127 0.58–0.65 3.2–4.5

1380 1294 799 450 337 197 124 0.62 3.7 P3 1421–1700 1294–1523 939–1117 558–635 406–482 228–279 127–152 0.73–0.75 3.8–4.6

1526 1399 1031 603 428 251 136 0.74 4.3

Female P1 1320–1624 1269–1472 1802–2005 812–964 761–888 635–787 279–330 1.3–1.4

1493 1394 1887 895 833 720 307 1.4

P2 1371–1700 1269–1624 761–914 406–533 305–381 203–232 102–152 0.56–0.60

1576 1479 858 482 353 208 127 0.58

P3 1523–1878 1371–1726 1041–1218 609–736 457–533 254–305 127–152 0.70–0.76

1742 1578 1147 676 496 279 143 0.73

Genitalia ( Figure 2D ). Sternite VIII with 14–21, 18 (7) setae on each side. Gonocoxite IX with 1–3, 2 (9) setae. Segment X without setae. Notum 175–188, 183 (3) µm long, 2.1 (3) times as long as ramus. Labium with microtrichia. Seminal capsule relatively large, 130–145, 139 (8) µm long, 1.1–1.2, 1.1 (8) times as long as broad, and 0.75–0.83, 0.78 (3) times as long as notum.

Pupa (n = 19). Total length 5.3–6.8, 6.1 mm.

Coloration. Exuviae largely pale brown.

Cephalothorax. Cephalic tubercles ( Figure 2E ) broadly rounded, 25–40, 34 (17) µm long, 0.25–0.32, 0.29 (17) times as long as basal width in mounted exuviae.

Abdomen ( Figure 2F ). Tergite I without spinules; II–V each with more or less extensive spinulation; VI with anterior and posterior transverse spinule bands; VII with anterolateral and posterolateral spinule patches; VIII and IX each with anterolateral spinules. Tergites II–VI each with anterior transverse band of brown and relatively large spines. Tergite II with row of 73–110, 91 caudal hooklets; its row 0.60–0.70, 0.65 times as long as tergal width. Paratergites II–V each with somewhat strong spinulation. Segment V with 3 Lt-setae on each side, VI–VII each with 4 Lt-setae; VIII with 5 Lt-setae. Anal comb ( Figure 2G ) with one large and 2–4, 3 small teeth. Anal lobe 270– 380, 329 µm long, 1.4–1.7, 1.5 times as long as broad, with 33–46, 39 lateral taeniae; dorsal seta absent. Male genital sac 1.2–1.3, 1.3 (6) times as long as anal lobe.

Fourth instar larva (n = 18). Body length 7.1–9.5, 8.2 (6) mm.

Coloration. Head capsule largely dark brown, with somewhat extensive white areas around eye spots, and body yellowish in alcoholic specimen.

Head. Length 444–515, 477 (5) µm long; cephalic index 0.71–0.78, 0.74 (5). Antenna 0.30–0.36, 0.33 (6) times as long as head capsule; lengths of first to sixth segments (µm): 80–88, 84 (10); 13–18, 15 (8); 18–20, 19 (8); 13–16, 13 (8); 10–13, 11 (8); 5–8, 7 (8). AR 1.1–1.4, 1.2 (8). First segment with ring organ located 0.18–0.24, 0.21 (10) from base; blade 83–93, 87 (4) µm long, and accessary blade 8 (1) µm long. Second and third segments each with Lauterborn organ 13–18, 15 (8) µm long. Third segment with style 8 (6) µm long. Labral lamella with 1 2–18, 15 (16) teeth. Pecten epipharyngis with 3 teeth ( Figure 2H ). Premandible ( Figure 2I ) 95–110, 103 (12) µm long, with 3 teeth. Mandible 165–188, 178 (11) µm long; seta subdentalis 43–45, 44 (5) µm long. Mentum ( Figure 2J ) 140–168, 156 (12) µm wide; median tooth bifid, pale, 30–43, 39 (17) µm wide. Ventromental plate 70–85, 80 (12) µm long, 110–128, 122 (12) µm wide, with 26–30, 27 (12) striae; distance between both plates 0.46–0.54, 0.50 (12) times as broad as width of mentum. Postmentum 175–200, 187 (17) µm long.

Body. With 8 anal setae.

Remarks. The male much resembles that of European M. britteni (Edwards) in the entirely dark brown foretibia, and the hypopygium with no median anal tergal seta, a triangular, apically pointed anal point, and lacking median volsellae. Additionally, the larval head capsule is largely dark brown as in the specimen deposited under the name of M. britteni in the Zoologische Staatssammlung Muenchen, Germany (M. Spies, pers. comm.). However, the species is separable from M. britteni by the pupal morphology. The cephalic tubercles are broadly rounded in the former, whereas relatively short, somewhat conical or dome-shaped in the latter ( Laville 1971: 202, fig. 7, a; Langton & Visser 2003, fig. 119e).

Judging from the pupal and larval morphology, M. shoukomaki belongs to the same group, M. pedellus group, as M. britteni ( Pinder & Reiss 1983 for the larva, 1986 for the pupa). Indeed, M. shoukomaki was misidentified as M. britteni by Sasa (1980: 29), who distinguished M. shoukomaki from M. britteni by the parallel-sided anal point in his key to males (Sasa 1998: 34, couplet 5). After re-examination of the holotype of M. shoukomaki , it was revealed that the anal point is not parallel-sided, but triangular and apically pointed. The reared Chinese material from Guangdong and Anhui Provinces also points to previous records of M. britteni by Qi & Wang (2006) being M. shoukomaki , and thus perhaps no true M. britteni exists in East Asia.

The male also resembles North American M. caducus Townes, 1945 in the thoracic scutum lacking acrostichal setae, the hypopygium without median anal tergal seta, and the triangular anal point, but differs in the dark brown thorax and the entirely darkened foretibia. In M. caducus , the thorax is light brown, and the foretibia is whitish medially, according to Townes (1945: 24).

The type series of M. ginzanefeus Sasa & Suzuki, 2001 comprises holotype and a single paratype. Reexamination of the type series showed that the holotype is a male of M. shoukomaki and the paratype is that of M. umbrosus . The original description is based not on the holotype, but on the paratype. Although the holotype is in too poor condition, the anal tergite with no median seta, the anal point tapering toward the apex, and the apically pointed superior volsella can be recognized ( Figure 5B ).

Figures

FIGURE 2. Microtendipes shoukomaki Sasa, male (A – C), female (D), pupa (E – G) and larva (H – J). A, Hypopygium, dorsal view; B, C, superior volsella, dorsal view, showing variation; D, genitalia, ventral view; E, cephalic tubercles; F, abdomen, dorsal view; G, posterolateral corner of abdominal segment VIII, dorsal view; H, pecten epipharyngis; I, dorsal head sclerites; J, mentum.

FIGURE 5. Microtendipes spp., male hypopygium. A, Holotype of Microtendipes tusimacedeus Sasa & Suzuki, NSMT-I-Dip 5139; B, holotype of Microtendipes ginzanefeus Sasa & Suzuki, NSMT No. 403: 51.