Cricotopus howensis 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 : 15-16

Cricotopus howensis Cranston sp. n.

( Figs 3 A, 4G, 6F, 9A, 11C)

urn:lsid:zoobank.org: act : A94258 F4-FF55-4F81-ABA8-0A8927739D77

Cricotopus “ howensis ” Cranston sp. nov. Cranston 1996: 87 [Invalid; author states ‘not formal publication for nomenclatural purposes]

Type material. Holotype Pe/♂, AUSTRALIA: Lord Howe Island, Rocky Run Ck., at coast, 31°33'S 159°05'E, 30.xi.1993 (Cranston & Gullan). Paratypes: ♀, 4Pe/♂, Le/ Pe♂, Le/ P♀, 3L/P, 13Pe, 12L, as Holotype; 4Pe, Erskine Valley, Erskine Ck., 31°34'S 159°04'E, 2.xii.1993 (Cranston & Gullan); 2Pe, upper Rocky Run Ck., 31°33'S 159°05'E, 28.x.2012 (Cranston & Gullan).

Other material examined. 10Pe, Erskine Valley, Erskine Ck., 31°34'S 159°04'E, 30.x.2012 (Cranston); Le/ P♀, 2L, upper Rocky Run Ck., 31°33'S 159°05'E, 28.x.2012 (Cranston).

Molecular material. P♀, Erskine Valley, Erskine Ck., 31°34'S 159°04'E, 30.x.2012 (Cranston) (Mv-LHI11); 2♀, Le/P♀, L, upper Rocky Run Ck., 31°33'S 159°05'E, 28.x.2012 (Cranston) (Mv-LHI12, 13, 15, 16).

Description. MALE (n=4, all teneral). 3.5mm. Thorax yellow-brown with contrasting dark vittae. Legs are teneral but may be substantially pale except for dark tarsomere 5.

Head. Ant 710–740 µm; Fl 1–12, 345–370 µm, Fl 13, 350–390 µm; A.R. 1.02–1.05. Palp 335–350 µm. 1–2 Fr, 8 Po, Clyp moderately setose.

Thorax. Mid-brown with vittae slightly darker. Laps 1–3, Ac 9–16, Dc 25–32 (longest posteriorly), Pa, 6–8, Scts 9–16.

Wing and legs teneral; sq 5–6.

Abdomen. TI, anterior 1/2 TII and IV pale, other tergites mid-brown.

Hypopygium ( Fig. 3 A). Gcx 180–195 µm, iv with small posteriorly projecting rounded lobe, apically bare. Gst 80–88 µm, about 1/2 (0.44–0.48) Gcx, pointed apically; crista dorsalis short, high, hyaline.

FEMALE (n = 2 + 2 pharate). 3.7 mm (n=1).

Head. Ant 325 µm. Palp 415–450 µm.?1 Co, 4–5 Fr, 6–8Po, Clyp strongly setose.

Thorax. Mid-brown, vittae darker and prominent. Laps 2–3, Ac 16, Dc 30 (longest posteriorly), Pa 5–6, Scts 14–23.

Wing (n=1, teneral). Sq 10, R + R1 12, R4+5 11.

Abdomen. As male.

Genitalia. Spermathecae comprising pale-brown, elongate-ovoid capsules with broad elongate"neck" abruptly tapering to thin recurved ducts; resembling C. varicornis ( Fig. 4 I) with shorter ducts.

PUPA. 3.4–4.0 mm, pale brown, adhesion scars scarcely darker.

Cephalothorax. Slightly rugulose postero-dorsally. Th 100–117 µm, width 20–27 µm; hyaline, sausage-shaped, tapering basally, tapering or rounded apically with few scales distally ( Fig. 6 F). Fs 72–75 µm, on prefrons.

Abdomen ( Fig. 9 A). PSB modestly developed on II and weak or absent on III. Hook row on TII about 0.5 segment width (0.45–0.52). Ls VIII short (38–50 µm), Ls4 about 1/7 (0.11–0.17) width of segment. Ms about 1/20 total length of abdomen (0.48–0.58). Adhesion scars pale brown.

4TH INSTAR LARVA ( Fig. 11 C). 4.2–4.9 mm. H.l. 420–460 µm, brown; mandibles, mentum and occipital margin only slightly darker brown than background; thorax yellow-green with some blue, abdomen strongly bluetinged; procercus tinged brown; procercal anal setae and posterior parapod claws brown.

Head. Ant 67–72 µm; 1, 42–45 µm; 2–5, 25–30 µm; A.R. 1.5–1.7; blade 20–23 µm not extending beyond 5th segment

Md 135–140 µm. 2x ant., outer margin moderately crenulate, mola curved distally with smooth inner margin, mid-brown gradually grading into slightly paler base; seta subdentalis broad, apically hooked.

Mentum 95–110 µm, mid-brown; 6 pairs laterals, 1st swollen, 2nd reduced near appressed to 1st.

Abdomen. l4 seta 30 µm, plumose at least on abd IV–VI. Pc short, with brown pigment patches, 17–25 µm, A.s. 450–500 µm.

Etymology. The epithet howensis , is an adjective derived for the only known location for this species which is endemic to Lord Howe Island, that lies in the Pacific Ocean 600 km due east of Port Macquarie on mainland New South Wales, eastern Australia.

Remarks. All adults of C. howensis are teneral, and the colour of body and legs cannot be determined unambiguously. It is possible that the thorax, abdomen and leg colour resembles that of C. albitarsis in both sexes ( Fig. 1 B). In the male hypopygium, the shape of the postero-medially directed inferior volsella, with a hyaline distal area may be distinctive. The female genitalia seem variable between specimens regarding the shape of the spermathecal vesicles and ducts The pupa has frontal setae on the prefrons, spinulose paratergite on segments III and IV, and the smooth thoracic horn tapers apically to a point. Larval C. howensis can be distinguished by the midbrown head capsule with mentum and mandible only slightly darker, and with mandibular dark pigment extending far basally. This is the only species present on Lord Howe Island, and adult Cricotopus found there should belong to this species.

Both creeks from which the species is reported are in excellent condition and likely to be permanent. The species was not found in cattle-contaminated water bodies.

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 3. Cricotopus male genitalia, part. A. C. howensis, B. C. parbicinctus (inset variation in inferior volsella above, gonostylus below), C. C. tasmania, D. C. varicornis, E. C. wangi. Tergite III, IV setation: F. C. varicornis, G. C. hillmani.

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 6. Cricotopus pupa, thorax and thoracic horns. A. C. albitarsis, B. C. annuliventris, C. C. brevicornis, D. C. conicornis, E. C. hillmani, F. C. howensis, G. C. parbicinctus, H. C. tasmania.

FIGURE 9. Cricotopus pupa, tergites. A. C. howensis, B. C. parbicinctus, C. C. tasmania, D. C. varicornis, E. C. wangi.

FIGURE 11. Cricotopus larva, mentum, mandible, antenna. A. C. conicornis, B. C. hillmani, C. C. howensis, D. C. parbicinctus.