Cricotopus acornis Drayson & Cranston

Drayson, Nick, Cranston, Peter S. & Krosch, Matt N., 2015, Taxonomic review of the chironomid genus Cricotopus v. d. Wulp (Diptera: Chironomidae) from Australia: keys to males, females, pupae and larvae, description of ten new species and comments on Paratrichocladius Santos Abreu, Zootaxa 3919 (1), pp. 1-40 : 5

Cricotopus acornis Drayson & Cranston , sp.n.

( Figs. 1 A, 2A, 4A, 8A, 10A)

urn:lsid:zoobank.org: act :EEBF8968-B52D-4344-A522-C9B5274FCAC7

Cricotopus ‘sp.B’ Drayson, 1992: 88

Cricotopus “ acornis ” sp. nov. Drayson & Cranston, in Cranston, 1996: 86 [Invalid; author states ‘not formal publication for nomenclatural purposes]

Type material. Holotype: Le/Pe/♂, AUSTRALIA: NSW, Jindabyne, Rush's Ck., 36°24'S 148°40'E, 12.xii.1987 (Cranston). Paratypes: 7 Le/Pe/♀, 2 Pe, as holotype. ACT: Le /Pe/♂, Pierce's Ck., Concrete Crossing, 35°20’S 148°56'E, 23.i.1991 (Drayson), ♀, Corin Rd, Gibraltar Falls, 35°28’S 148°55'E, 28.ix.1990 (Drayson). Vic: 2Le/ Pe/♀, Pe/♀, 10 km E. Mitta, Mitta R., 36°32'S 147°25’E, 30.x.1989 (Cook); Le/Pe/♂, Buckland R., 36°48’S 146°51'E, 6.xi.1990 (Cranston, Cook & Nielsen); Pe, Cann R., 37°34’S 149°09'E, 20.i.1989 (Cranston).

Other material examined. 7L, as Holotype.

Description. MALE ( Fig. 1 A) (n=2). 3.0– 3.1 mm.

Head. Ant 792–864 µm; Fl 1–12 340–424 µm; Fl 13 432–440 µm. A.R. 1.03–1.20. Palp 432–376 µm. 1–2 Fr; 10–13 Po. Clyp sparsely setose.

Thorax. Mid-brown, sct sometimes pale brown, almost hyaline, with mid-brown border. Laps 4–8, Ac 22–32, Dc 17–22, Pa 3–6, Scts 8–12.

Wing. 2.0 mm. Sq 7–13, R 7.

Legs. All legs uniform mid-brown.

Abdomen. Uniform mid- to pale brown.

Hypopygium. Gcx 178 µm (n=1); iv rounded and notched posteriorly. Gst 76 µm (n=1), about 2/5 (0.43) Gcx, narrow apically; crista dorsalis strongly developed.

FEMALE (n = 2 + 3 pharate). As male except: 3.0– 4.7 mm.

Ant 320–355 µm. Palp 400–420 µm.

Wing. 1.8–2.6 mm. Sq 6–10, R,12–13, R4+ 5 8–15.

Abdomen. Brown.

Genitalia. Spermathecae comprising mid-brown, ovoid, capsules, narrow "neck" and straight or recurved ducts ( Fig. 4 A).

PUPA. 3.5–4.4 mm, pale brown to very pale, almost hyaline.

Cephalothorax. Slightly rugose. Thoracic horn absent. 0 Fs.

Abdomen ( Fig. 8 A). PSB only on II. Hook row never> 0.5 segment width (0.38–0.50). L4 seta on VIII> 1/7 segment width (0.14–0.22). Ms 140–180 µm, <1/15 abdomen length (0.048–0.064).

4TH INSTAR LARVA ( Fig. 10 A) (n = 9). 2.8–3.8 mm. H.l. 520–580 µm pale to mid-brown, abdomen hyaline.

Head. Ant 68–80 µm: seg 1 44–52 µm; seg 2–5 22–30 µm; A.R. 1.60–1.85. Md 52–174 µm, with serrate inner and crenulate outer margin, dark brown with distal 1/3 very dark brown. Mentum 124–136 µm, pale brown posteriorly, mid-brown anteriorly, with 6 pairs of laterals, 2nd much reduced.

Abdomen. Pc 15–22 µm, A.s. 540–650 µm.

Etymology. The epithet refers to the pupa lacking (a-) a thoracic horn (-cornis).

Remarks. Adult males of C. acornis sp. n. can be recognised by the combination of uniformly dark abdomen and legs and notched inferior volsella: females can be recognised by uniformly dark tergites and legs and near spherical spermathecal capsules. Pupae lack thoracic horns but otherwise resemble C. parbicinctus in lacking frontal setae, and having non-spinose TI and II. Differentiation can be made based on the presence of small patches of spines/spinules postero-lateral on tergites VI–VI in C. acornis . Note that some pupae of any species can ‘lose’ their thoracic horns during drift post-emergence or in subsequent handling, even in slide preparation, and identity as C. acornis should not be assumed. Larvae can be recognised by the mandible with a crenulate outer margin, smooth inner margin and being wide above the mola.

C. acornis sp. n. was collected first from an ephemeral stream that had ceased flow on a subsequent visit. Other records are scarce, from mid-order creeks and rivers in a restricted area of south-eastern Australia. No material for molecular study was collected.

Figures

FIGURE 1. Cricotopus adult males. Columns (left to right): legs, anterior to posterior; thorax; dorsal abdomen. A. C. acornis, B. C. albitarsis, C. C. annuliventris, D. C. brevicornis, E. C. conicornis, F. C. hillmani, G. C. parbicinctus, H. C. tasmania, I. C. varicornis.

FIGURE 4. Cricotopus female. Spermathecae. A. C. acornis, B. C. albitarsis, C. C. annuliventris, D. C. brevicornis, E. C. conicornis, F. C. hillmani, G. C. parbicinctus, H. C. tasmania, I. C. varicornis.

FIGURE 8. Cricotopus pupa, tergites. A. C. acornis, B. C. albitarsis, C. C. annuliventris, D. C. brevicornis, E. C. conicornis (reticulations shown only on part TVIII), F. C. hillmani

FIGURE 10. Cricotopus larva, mentum, mandible, antenna. A. C. acornis, B. C. albitarsis, C. C. annuliventris, D. C. brevicornis.