Cryptochironomus imitans, Saether, Ole A., 2009

Saether, Ole A., 2009, Cryptochironomus Kieffer from Lake Winnipeg, Canada, with a review of Nearctic species (Diptera: Chironomidae), Zootaxa 2208, pp. 1-24 : 15-19

Cryptochironomus imitans sp. n.

( Fig. 4 B–D; 7)

Cryptochironomus sp. n. A, Chang et al. 1993. Cryptochironomus sp. n. C, Chang et al. 1994.

Type material. Holotype male, CANADA: Quebec, Gatineau Park, Lusk Cave, reared from larva, on logs in pool inside cave, 29.vi. 1966, A.L. Hamilton and J. Martin ( CNC). Paratypes: CANADA: Manitoba, Pinawa, Winnipeg River, female reared from larva, 2.vii 1967, J. Ireland; Ontario, Lake Ontario, Bay of Quinte, Halton, male reared from pupa, 29.vii. 1968, W.F. Warwick; Ontario, Kenora, Experimental Lakes Area, Lake 172, mature male pupa, 26.vii 1968, S.S. Chang; Lake Winnipeg records: Pine Dock, 20 males, 10. & 31.vii. 1969; 3 km off Grand Rapids, 1 male, 13.vii. 1969; 10 km off (Sturgeonskin) Long Point, 3 males, 14.vii. 1969; Gull Harbour, 1 males, 16.vii. 1969; Victoria Beach, 3 males, 25.vii. 1969; Grand Rapids Government Wharf, 5 males, 28.vii. 1969; Beaver Point, 2 males, 30.vi.–19.viii. 1971; Old Fishing Dock, 8 males, 29.vi.– 18.viii. 1971; Hecla Island, 2 males, 24 & 25.viii. 1971; Beaver Creek, 1 male, 8.vi. 1971; 3 km southeast Bushgega Island, 1 male, 31.vii. 1969; North Basin, 1 larva, 9.vii. 1969.

Diagnostic characters. The imagines are characterized by a wing length of 2.02–2.81, male AR of 2.52– 3.05, LR1 of 1.56–1.83, presence of as long as wide to twice as is long as wide frontal tubercles or at least of ocelli, and hypopygium of C. fulvus type.

The female has 7 sensilla chaeticae on mid leg, 3 on hind leg; gonocoxite IX without setae; and segment X with 3 setae on each side.

The pupa is 5.1–6.3 mm long; has a simple 0.10–0.14 mm long cephalic tubercle with 31–60 µm long frontal seta; T I with distinct, T II–III with weak, and T IV–VI with barely indicated reticulation; caudal spines on T II–VII or VIII and S II–VIII; and 39–52 filaments in fringe of anal lobe.

The fourth instar larva has a head capsule length of about 0.43–0.44 mm, a postmentum length of about 160–180 µm, ventromental plates 2.6–2.7 times as wide as long, AR of 1.0–1.2, and apical tooth of mandible about 0.23 times as long as mandible.

Etymology: From Latin imitans , imitate, copy, referring to the similarity with several other species.

Male imago (n = 10–12, except when otherwise stated)

Total length 4.67–5.80, 5.35 mm. Wing length 2.02–2.81, 2.46 mm. Total length/Wing length 1.93–2.32, 2.15. Wing length/length of profemur 2.31–2.43, 1.37.

Head. AR 2.52–3.05, 2.76 µm (54). Temporals 29–41, 34. Clypeus with 11–25, 16 setae. Tentorium 149– 180, 159 µm long. Stipes 160–200, 177 µm long. Frontal tubercles ( Fig. 4 B) 10–25, 15 µm high; 7–13, 9 µm wide. Palp lengths (in µm): 38–57, 47; 52–80, 65; 163–203, 189; 133–176, 157; 210–273, 237.

Thorax. Antepronotum with 7–13, 10 setae. Dorsocentrals 12–23,16; acrostichals 14–20, 17; prealars 4–7, 5. Scutellum with 12–25, 19 (63) setae.

Wing. VR 1.08–1.12, 1.10. Brachiolum with 2–4, 3 setae; R with 18–35, 24; R1 with 11–19, 16; R4+5 with 18–39, 27 setae. Squama with 8–19, 14 (52) setae.

Legs. Sensilla chaeticae 1–5, 3 (47) on mid leg; 0–3, 1.8 (51) on hind leg. Lengths and proportions of legs as in Table 2.

fe ti ta1 ta2

p1 874–1177, 1037 672–908, 820 1042–1513, 1351 572–723, 642

p2 840–1042, 961 740–1034, 914 452–638, 559 223–292, 264

p3 925–1177, 1074 992–1345, 1188 680–941, 832 347–442, 401 ta3 ta4 ta5 LR

p1 415–580, 519 286–469, 407 136–200, 166 1.56–1.83, 1.64(44)

p2 173–231, 204 107–143, 125 73–100, 89 0.58–0.63,0.61

p3 286–360, 329 163–197, 182 93–117, 106 0.68–0.72, 0.70

BV SV BR

p1 1.78–2.00, 1.86 1.33–1.48, 1.39 2.27–2.95, 2.48

p2 3.18–3.94,12.58 3.21–3.58, 3.36 3.03–4.10, 3.61

p3 2.84–3.36, 3.04 2.63–2.82, 2.72 4.18–6.13, 5.11

Hypopygium ( Fig. 4 C). T IX with 30–45, 37 setae; laterosternites IX each with 4–6, 6 setae. Phallapodeme 134–170, 151 µm long. Transverse sternapodeme 78–107, 91 µm long. Gonocoxite 137–213, 168 µm; gonostylus 133–183, 155 µm long. HR 1.03–1.18, 1.08; HV 2.86–3.73, 3.40.

Female imago (n = 1)

Total length 3.69 mm. Wing length 2.14 mm. Total length/wing length 1.72. Wing length/length of profemur 2.19.

Head. AR 0.43. Flagellomeres length (microns): 90, 49, 50, 57, 98. Temporals 13. Clypeus with 13 setae. Tentorium 84 µm long. Stipes 106 µm long. Ocelli 4 µm high, 4 µm wide, 34 µm apart. Palpomere lengths (in µm): 32, 46, 103, 100, 149.

Thorax. Antepronotum with 8 setae. Dorsocentrals 23, more than 10 acrostichals, prealars 5. Scutellum with 25 setae.

Wing. VR 1.17. Brachiolum with 2 setae, R with 29; R1 with 28, R4+5 with 53 setae. Squama with 13 setae. Legs. Sensilla chaeticae 7 in apical 1/2 of ta l of mid leg, 3 on ta1 of hind leg. Lengths and proportions of legs as in Table 3.

fe ti ta1 ta2 ta3 ta4 ta5 LR BV SV BR p1 975 761 – – – – – – – – – p2 859 791 515 215 159 92 76 0.65 4.01 3.19 3.19 p3 908 1006 717 319 245 144 92 0.71 3.27 2.67 3.41 Genitalia ( Fig. 4 D). Cercus 118 µm long. Gonocoxite IX bare. T IX with 46 setae. Segment X with 3 setae on each side. Notum 180 µm long. Seminal capsule 120 µm long, 90 µm wide.

Pupa (n = 4, except when otherwise stated)

Total length 5.09–6.29, 5.80 mm.

Cephalothorax. Cephalic tubercles ( Fig. 7 B) simple, 100–140, 130 µm long; 50–120, 71 µm wide at base; 12–13, 12 µm wide at frontal seta; frontal seta 31–60 µm (3) long.

Abdomen ( Fig. 7 A). T I distinctly, T II–III weakly, T IV–VI barely and faintly reticulated. Shagreen and chaetotaxy as illustrated. Caudal margin of T II with 26–30, 30 hooklets to each side of 100–140, 123 µm wide mesal interruption. Pedes spurii A present on S IV–VII; longest spinules 22–26, 24 µm on IV; 10–12, 10 µm on V–VII. Caudal margins of T II–VIII respectively with the following numbers of spines (lengths in parentheses): 10–35, 25 (4–10, 8 µm); 38–60, 48 (10–18, 15 µm), 33–60, 46 (14–29, 18 µm); 35–62, 49 (16– 21, 18 µm); 21–60, 40 (11–19, 15 µm); 17–48, 30 (10–20, 14 µm); 0–10, 3 (0–4 µm). Caudal margins of S II– VIII with the following numbers of spines (lengths in parentheses): 33–37, 35 (10–14, 12 µm); 22–39, 30 (10–12, 12 µm); 17–26, 22 (6–10, 9 µm); 12–23, 19 (8–17, 13 µm); 19–6, 22 (8–20, 14 µm), 14–32, 21 (14– 22, 20 µm); 16–54(3) (14–22 µm (3)) in male, none in female. Caudomedian projection of anal lobe 160–200, 183 µm long, 200–220, 20 µm wide; with 52–66, 60 µm long, 10–17, 13 µm wide branches. Genital sac of male with 14–15 µm (3) long, 14–15 µm (3) wide, rounded apical point; apical point of female genital sac 42 µm by 42 µm. Fringe of anal lobe with 39–52, 46 filaments.

Fourth instar larva (n = 1–2)

Head capsule length 0.43–0.44 mm.

Head. Antenna as in Fig. 7 C. Lengths of antenna] segments (in µm): 72–76, 30–36, 24–30, 2–3, 2–3. AR 1.07–1.24. Basal antennal segment 22 µm wide, 2.11–2.40 times as long as second segment; ring organ 42–46 µm from base. Preapical blade of second segment 32–38 µm long, apical style 9–12 µm long. Labrum ( Fig. 7 D) with 26–36 µm long labral sensilla, S I 26 µm long, S II 34 µm long. Premandible 92–104 µm long. Mandible ( Fig. 7 E) 120 µm long, with 28–33 µm long apical tooth which is 0.23 times as long as mandible. Basal segment of maxillary palp 56–58 µm long, 18–20 µm wide. Median tooth of mentum ( Fig. 7 F), including darker lateral accessory teeth, 40 µm wide. Ventromental plate 130 µm wide, 48–50 µm, long, 2.60– 2.71 times as wide as long. Postmentum 160–180 µm long.

Abdomen. Procercus 26 µm high, 26 µm wide, with 505 µm long anal setae. Supraanal seta 410 µm; Supraanal seta/anal setae 0.81. Anal tubules triangular, 180 µm long, 90 µm wide at base.

Figures

FIGURE 4. Cryptochironomus ramus Mason (A) and Cryptochironomus imitans sp. n. (B – D), imagines. A, C — male hypopygium; B — frontal tubercles; D — female genitalia.

FIGURE 7. Cryptochironomus imitans sp. n., pupa (A, B) and larva (D – F). A — tergites; B — cephalic tubercles; C — antenna; D — labrum and epipharynx; E — mandible; F - mentum.