Cryptotendipes darbyi (Sublette)

Saether, Ole A., 2010, Cryptotendipes Lenz from Manitoba, Canada, with keys to known immatures of the genus (Diptera: Chironomidae), Zootaxa 2412, pp. 1-20 : 12-14

Cryptotendipes darbyi (Sublette)

( Fig. 6 )

Tendipes darbyi Sublette, 1960: 221 .

Tendipes ariel Sublette, 1960: 222 , syn. n.

Material examined. USA: South Dakota, Lewis and Clark Lake, Gavins Point Dam, 2 males, 30.iv. –13.v. 1951, P. L. Hudson. CANADA: Manitoba, Delta Marsh, Portage Creek, 4 males reared from pupae, female reared from pupa, pupal exuviae, 17.vi. –27.viii. 1967, W.M. Hominick (as Harnischia sp in Hominick & Welch 1971); Manitoba, St. Alphonse, shallow lake, male reared from pupa, female reared from pupa, 23.v. 1968, J. F. Flannagan & A. L. Hamilton. Lake Winnipeg records: Victoria Beach, 326 males, 9. & 25.vii. 1969; north of outer buoy Red River, 4 males, 9.vii. 1969; 0.5 km off George Island, 1 male, 11.vii. 1969; 10 km off Sturgeonskin (Long) Point, 9 males, 14.vii. 1969; Gull Harbour, 25 males, 16.vii. 1969; Gimli Government Warf, 1 male, 24.vii. 1969; centre of South Basin, 2 males, 25.vii. 1969; 3 km off George Island, 14 males, 27.vii. 1969; Grand Rapids Government Warf, 1 male, 28.vii. 1969; 5 km of Selkirk (Horse) Island, 3 males, 29.vii. 1969; McBeth Harbour, 40 males, 7.ix. 1969; 3 km off Grand Rapids, 14 males, 4.ix. 1969; 15 km off Long Point, 2 males, 6.ix. 1969; Gimli Government Warf, 1 male, 9.ix. 1969; Beaver Point, 7 males, 27.vii. –19.viii. 1971; Old Fishing Dock, 67 males, 14.vii. –18.viii. 1971; Calder’s Dock, 89 males, 6.vii. – 26.viii. 1971; Hecla Island, 80 males, 27.vii. –25.viii. 1971; 1 km off Elk Island, 1 male, 29.vii. 1969; off Grand Marais Point, 1 male, 9.ix. 1969; South Basin, 30 pupae, 422 larvae, 9.vii. –31.x. 1969; Narrows, 5 pupae, 25 larvae, 4.vi. –31.x. 1969; North Basin, 3 pupae, 368 larvae, 4.vi. –31.x. 1969.

The male imagines examined have an AR of 1.83–2.50, 2.16 (28); 2-–7, 4(10) sensilla chaetica on p2 and none on p3. The male hypopygium is illustrated by Saether (1977a fig. 34E). As mentioned by Saether (1977a: 98), Hudson (1971:159) referring to Sublette (personal communication) suggested that C. ariel was a mounting variation of C. darbyi . The present specimens show that C. ariel has to be regarded as a synonym of C. darbyi . The variation is not only based on a variation in preparation, but is a true variation. Sublette (1960: 221–222) gives the AR of C. darbyi as 2.50–2.82, of C. ariel as 3.17–3.50. However, these ratios are probably too high since not all antennae were slide-mounted, but the AR measured on pinned specimens. The examined specimens with hypopygium of the C. " ariel " type generally have a higher AR than those with a typical C. darbyi hypopygium. However, all gradations and intermediates are present and also the immatures show a very high variability.

The female imago has 22 sensilla chaetica on p2, 7 on p3. Its genitalia are illustrated by Saether (1977b fig. 85 D–E).

Pupa (n = 12, except when otherwise stated)

Total length 4.24–5.81, 4.93 mm. Exuviae yellowish grey with darker thorax.

Cephalothorax. Thoracic horn 2.27–3.35, 2.77 mm long; main stem 0.47–1.14, 0.76 mm long. Cephalic tubercle 60–130, 83 µm high; 42–96, 63 µm wide; with 44–100 µm long frontal seta.

Abdomen ( Fig. 6 A, B). Shagreen and chaetotaxy as illustrated. Caudal margin of T II without hooklets. Numbers of caudal spines on T II-VIII: 26–51, 33; 19–31, 26; 16–27, 20; 21–48, 29; 25–48, 36; 14–30, 22; 18–44, 24. Lengths of caudal spines on T II–VIII (in µm): 10–34, 21; 20–48, 34; 20–60, 40; 26–66, 45; 22– 63, 43; 12–23, 18; 6–11, 9. S I apparently without spinules. Numbers of caudal spines on S II–VIII: 0–12, 5; 10–26, 16; 14–28, 19; 14–29, 21; 14–36, 21; 15–44, 25; 45–80, 58 (9) in males, none in females. Lengths of caudal spines on S II 8–20, 12 µm; on S III–VIII 12–42, 25µm. T VIII with 30–130, 83 µm (10) long spur; 8– 12, 10 µm (10) wide at base; located 74–100?, 89 µm (10) from caudolateral corner. Taeniate L-setae on V– VIII: 3–4, 3; 4; 4; 3–4, 3. Genital sac of male with 70–140, 90 µm (8) long apical point, overreaching anal lobe by 142–200?, 173 µm (8); of female with 85-110 µm (3) long apical point, overreaching anal lobe by 105–160 µm (3). Anal lobe with 19–26, 24 (11) taeniae of about equal width and color.

Fourth instar larva (n = 10, except when otherwise stated)

Total length 3.09–8.19, 5.92 mm (170). Head capsule length 0.30–0.41, 0.36 (816). Head capsule brownish yellow with about 70–100, 83 µm long, 140–180, 153 µm wide brown ventral spot.

Head. Antenna as in Fig. 6 C. Lengths of antennal segments (in µm): 45–60, 55; 12–16, 13; 5–9, 7; 9–12, 11; 5–8, 6. AR 1.44–.82, 1.57. Basal antennal segment 18–22, 21 µm, wide; ring organ 14–20, 17 µm, from base; blade 22–32, 25 µm; accessory blade 14–22, 18 µm long. Apical style of second segment 6–11, 8µm long. Labrum with S I 18–34, 24 µm, long; S II 26–38, 33 µm, long. Premandible 82–92, 86 µm long. Mandible ( Fig. 6 D) 126–148, 137 µm, long. Maxilla and palp as in Fig. 6 E. Median tooth of mentum ( Fig. 6 F) 20–26, 24 µm wide; three median teeth combined (or median tooth with lateral notches) 33–45, 39 µm wide; mentum when flattened 110––150, 130 µm wide. Ventromental plate 84–114, 99 µm wide; 37–54, 44 µm long. Postmentum 185–219, 206 µm long.

Abdomen. At least some abdominal segments with small tuft of setae. Procercus 22–40, 30 µm high; 24– 31, 28 µm wide; with 613–761, 665 µm long anal setae. Supraanal seta 340– 430, 390 µm; supraanal seta/anal setae 0.54–0.63, 0.58. Anal tubules 105–156, 116 µm long; 42–70,54 µm wide at base. Posterior parapods 200–221, 211 µm long.

Third instar larva

Total length 2.89––4.80, 3.39 mm (15). Head capsule length 0.17–0.23, 0.21 mm (303).

Second instar larva

Head capsule length 0.13–0.15, 0.14 mm (6). For distribution of head capsule lengths between instars see also Fig. 8 .

Distribution and ecology. The species was previously known from Finland, British Columbia, Manitoba, South Dakota, Kansas, Idaho, California, Nevada, Arizona and New Mexico ( Gillespie 1974, Sublette 1960, Darby 1962, Hudson 1971, Oliver et al. 1990, Saether & Spies 2004). It has been found in rice fields and in lakes. In Lake Winnipeg it is one of the most common species.

Figures

FIGURE 6. Cryptotendipes darbyi (Sublette), immatures. A – pupal tergites; B – pupal sternites; C – larval antenna; D – larval mandible; E – maxilla and maxillary palp; F – mentum.

FIGURE 8. Head capsule lengths of different instars of Cryptotendipes darbyi (Sublette) and Cryptotendipes casuarius (Townes) in Lake Winnipeg.