Cryptochironomus stylifera (Johannsen)

Saether, Ole A., 2009, Cryptochironomus Kieffer from Lake Winnipeg, Canada, with a review of Nearctic species (Diptera: Chironomidae), Zootaxa 2208, pp. 1-24 : 5-9

Cryptochironomus stylifera (Johannsen)

( Figs 2 A–G; 3 A, B)

C hironomus stylifera Johannsen, 1908: 281 .

C hironomus obtusilobus Malloch, 1923: 171.

C hironomus farinalis Walley, 1926: 205.

Cryptochironomus psittacinus Townes, 1945:100 ; Chang et al 1994: 13; not Meigen, 1830: 247; not Reiss, 1968: 196.

Tendipes (Cryptochironomus) redekei Kruseman, 1933: 187 ; Ringe 1970: 312; syn. n.

Material examined. CANADA: Saskatchewan, Stoney Lake, about 50 miles north of North Battleford, female reared from larva, 31.vii.1968, J.F. Flannagan. Manitoba, Delta Marsh, Portage Creek, male reared from larva, 19. vi. 1968, W.M. Hominick; Lake Winnipeg records: Victoria Beach, 90 males, 9. & 25.vii. 1969; NNE of Reindeer Island, 1 male, 11. ii. 1969; 3 km off Grand Rapids, 7 males, 13.vii & 4. x. 1969; 3 km off McCreary Island, 5 males, 15.vii. 1969; Gull Harbour, 11 males, 1 female, 16.vii. 1969; Gimli Government Wharf, 1 male, 24.vii. 1969; Matheson Island Government Wharf, 1 male, 26.vii. 1969; 3 km off George Island, 22 males, 27.vii. 1969; Grand Rapids Government Wharf, 1 male, 28.vii. 1969; 5 km of Selkirk (Horse) Island, 8 males, 29.vii. 1969; McBeth Harbour, 214 males, 7.ix. 1969; Pine Dock, 2 males, 31.vii. 1969; Beaver Point, 10 males, 30.vi. & 6.viii. 1971; Old Fishing Dock, 36 males, 16.vi.–18.viii. 1971; Calder’s Dock, 5 males, 24.vi.–31.viii. 1971; Hecla Island, 6 males, 27. vii. & 11.viii. 1971; off Pearson Reef, 2 males, 27.x. 1969; South Basin, 16 larvae, 9.vii.–31.x. 1969; Narrows, 7 larvae, 4.vi.–31.x. 1969; North Basin, 56 larvae, 1 pupa, 4.vi.–31.x. 1969.

As mentioned by Saether (1977a: 87) C. psittacinus (Meigen) in the sense of Townes (1945: 100) is probably not identical with C. psittacinus in the sense of Reiss (1968: 196). C. psittacinus in the sense of Townes, however, probably is identical to Cryptochironomus redekei which than will be a junior synonym of C. stylifera .

The Lake Winnipeg males have an AR of 4.35–5.12, 4.76 (10); LR1 of 1.12–1.21, 1.18(10); 9–20, 14 (10) sensilla chaeticae on p2 and 0–3, 0.6 (10) on hind leg; and 12–20, 16 (10) setae on squama. The frontal tubercles are shown in Fig. 2 A. The shape of the gonostylus is quite variable, ranging from a shape similar to that of C. digitatus (Malloch) to the typical distinctly broadened apex ( Fig. 2 B).

The female genitalia are illustrated by Saether (1977b fig. 90C). Two intersexes with female antennae have 84–98 sensilla chaeticae on mid leg, and 90–100 on hind leg, indicating that) this is the normal range for a female (see Saether & Galloway (1977).

Cryptochironomus redekei ( Kruseman) (Kruseman 1933: 187, Ringe 1970: 312) appears to be a synonym of C. stylifera . Reiss's C. psittacinus has a LR1 as in C. stylifera . The AR and the hypopygium, however, appear to be more in accordance with C. digitatus .

The pupae examined here have reticulation anteriorly and laterally on tergite VI, laterally on VII and VIII, and the posterior thoracic mound is bifid. Except that the reticulation not is quite complete on tergite VI the pupa thus will key to C. redekei in the key to pupae and larvae in Vallenduuk & Morozova (2005). The larva keys directly to C. redekei fitting in all details.

Pupa (n = 5, except when otherwise stated)

Total length 10.80–13.00, 11.87 mm.

Cephalothorax. Cephalic tubercle ( Fig. 3 A) 339–552, 453 µm long; 76–98, 88 µm (4) wide from base; 36–55, 44 µm wide 2/3 from base; with or without an 18–25 µm (2) long frontal seta. Posterior thoracic mound at least sometimes bifid.

Abdomen ( Fig. 3 B). T I–V, anterior portion of T VI, S I–V and margins of S VI–VIII with reticulation. Shagreen and chaetotaxy as illustrated. Caudal margin of T II with 45–55, 52 hooklets to each side of a 126– 210, 163 µm wide interruption. Pedes spurii A present on S IV–VII; spinules 42–60, 50 µm long on IV; 14– 22, 20 µm on V–VII. Caudal margins of T I–VIII respectively with the following number of spines (lengths in parenthesis): 23–34, 28 (16–62, 42 µm); 20–43, 33 (20–72, 47 µm); 18–23, 22 (52–90, 65 µm); 18–26, 22 (42–80, 58 µm); 16–26, 22 (66–88, 72 µm); 18–26, 23 (67–78, 72 µm); 19–23, 22 (53–62, 59 µm); male with 16–110, 77(4) (13–24, 16 µm (4)), female without. Caudal margins of S I–VII respectively with the following numbers of spines (lengths in µm in parentheses): 0–22, 14 (0–44, 24 µm); 5–17, 11 (16–56, 35 µm), 20–23, 22 (30–70, 55 µm); 14–23, 19 (40–77, 53 µm); 6–17,12 (28–60, 43 µm); 2–16, 8 (14–23, 20 µm); 0–15, 6 (0– 32, 14 µm). Caudomedian projection of anal lobe 307–368, 336 µm long; 270–331, 297 µm wide; with 81– 120, 97 µm long, 20–38, 25 µm wide branches. Genital sac of male with 52–78 µm (3) long, 42–60 µm (3) wide apical point; female without a set off apical point. Each fringe of anal lobe with 110–131, 118 filaments.

Fourth instar larva (n = 9–11, except when stated otherwise)

Total length 8.75–14.24, 10.54 mm. Head capsule length 0.80–1.02, 0.90 mm (78).

Head. Antenna as in Fig. 2 C. Lengths of antennal segments (in µm): 82–102, 92; 30–38, 35; 24–34, 30; 4–5, 4; 46,5. AR 1.10–1.32, 1.23. Basal antennal segment 33–38, 36 µm wide; 2.37–3.00 times as long as second segment; ring organ 46–62, 55 µm from base. Blade preapical on second segment 34–46, 40 µm (5) long; apical style 10–12, 11 (7) long. Labrum ( Fig. 2 D) with labial sensilla 36–46, 42 µm (7) long; S I 30–46, 39 (8) and S II 60 –70, 67 µm (6) long. Premandible ( Fig. 2 E) 170–205, 190 µm long. Mandible ( Fig. 2 F) 222–290, 261 µm long; with 50–72, 60 µm long apical tooth which is 0.19–0.25, 0.24 times as long as mandible. Basal segment of maxillary palp 66–80, 70 µm long; 24–30, 28 µm wide. Median tooth of mentum ( Fig. 2 G) including darker lateral accessory teeth 68–74, 71 µm wide. Ventromental plate 200–260, 239 µm wide; 58–74, 66 µm long; 3.29–3.85, 3.61 times as wide as long. Postmentum 320–380, 352 µm long. Gula without obvious pigmentation. Postoccipital margin darkish yellow.

Abdomen. Procercus 44–60, 50 µm (7) high; 44–66, 51 µm (7) wide; with 540–613, 583 µm (6) long anal setae. Supraanal seta 540–613, 583 µm (6); supraanal seta/anal setae 0.56–0.70, 0.63(5). Anal tubules triangular; 210–280, 244 µm long; 100–141, 121 µm wide at base. Posterior parapods 429–564, 482 µm (4) long.

Third instar larva

Head capsule length 0.49–0.55, 0.51 mm (14) (See Fig. 9 ).

Second instar larva

Head capsule length 0.28–0.31 mm (2) (See Fig. 9 )

Distribution and ecology. C. stylifera was previously known from Alaska to New York and south to Oregon, and Florida ( Townes 1945:101, Sublette and Sublette 1965: 168, Oliver et al. 1990: 44, Epler 2009; all as C. psittacinus ). The species is probably also present in Europe (as C. redekei , see above).

Figures

FIGURES 2. Cryptochironomus stylifera (Johannsen), male (A, B) and larva (C – G). A — frontal tubercles; B — hypopygium; C - antenna; D — labrum and epipharynx; E — premandible; F — mandible; G — mentum.

FIGURE 3. Cryptochironomus stylifera (Johannsen), pupa (A, B) and Cryptochironomus digitatus (Malloch), pupa (C) and larva (D – G). A — cephalic tubercles; B — tergites; C - cephalic tubercles; D — antenna; E — labrum and epipharynx F — mandible; G - mentum.

FIGURE 9. Head capsule lengths of the four most common species of Cryptochironomus Kieffer in Lake Winnipeg.