Culex (Culex) cuyanus Duret, 1968: 323

Rossi Erika Scheibler, Gustavo C. & Dominguez, Martha C., 2006, Morphological descriptions of the female, pupa, and larva of Culex (Culex) cuyanus Duret (Diptera: Culicidae), Zootaxa 1165, pp. 47-55 : 48-54

Culex (Culex) cuyanus Duret, 1968: 323

Holotype: Male ( USNM). Type locality: Argentina, Jachal , San Juan Province.

FEMALE: Head: Proboscis 1.98–2.84 mm (mean 2.28 mm; SD 0.3) mostly darkscaled with pale scaling on ventral surface from near base to 0.70. Maxillary palpus entirely dark­scaled, length 0.35–0.44 mm (mean 0.37 mm) including vestigial fourth palpomere. Antennal pedicel yellowish but dark brown on medial portion, with few small scales; proximal 0.65 of first flagellomere yellowish, remainder dark. Antenna as long as proboscis, 2.20–2.42 mm (mean 2.33 mm). Occiput with sparse narrow, decumbent scales in central area, lateral patch of broad scales, erect, forked scales black. Ocular and interocular setae dark. Thorax: Integument light brown. Scutum covered with small, falcate, coppery scales with golden reflections, longer whitish scales on prescutelar area, and some inconspicuous whitish scales on anterior promontory, scutal angle, antealar area, and supraalar area. Scutal setae brown. Scutellar scales whitish (3 patches), lateral lobes each with 5–6 (5) large setae, median lobes with 6–8 (6) long setae. Pleural integument light brown. Antepronotum with scattered, narrow, light brown scales and 8–11 (9) dark brown setae. Postpronotum with light brown scales and 3–4 (4) dark setae in curved row. Proepimeron bare. Upper proepisternum with numerous setae and patch of whitish scales. Upper mesokatepisternum with row of 6–7 setae and patch of broad whitish scales, lower area with 2 setae and patch of broad whitish scales. Mesepimeron with 1 lower seta, 4–6 upper setae and anterior patch of whitish scales at level of upper mesokatepisternum. Paratergite bare. Wings: Length 3.87–4.25 mm (mean 4.10 mm), scales dark brown with patch of whitish scales that extend from base of costa to humeral cross­vein. Halter: Scabellum and pedicel yellowish, capitellum pale at base and dark brown apically with few whitish scales. Legs: Forecoxa with patch of dark scales at base and middle, midcoxa with patch of dark scales apically. Trochanters yellowish with small transverse black line at apex. Femora dark­scaled except for pale scales on posterior surface, extending from base to beyond middle of forefemur, from near base to near middle length of midfemora, and near base to apex of hindfemora, with pale scales at articulation with tibiae. Anteroventral surface of fore­, mid­ and hindtibiae with white scales forming longitudinal stripe. Tibio­tarsal joint with patch of scales more visible in hindleg, mid­ and hindtarsi with some hyaline scales at apex, ungues simple and small, pulvilli pale. Abdomen: Tergum I with posteromesal patch of dark scales, golden setae. Terga with dark brown scales. Tergum II with basolateral spot of white scales. Terga III, VIII with basal pale band joined to basolateral spot, basal bands of male wider than those of female, with goldenbrown setae. Sterna II­VIII mainly yellowish, with 1 or 2 lines of dark scales apically.

PUPA ( Fig. 1): With characters of the genus. Setae as figured, range and mode of setal branches given in Table 1. Cephalothorax. Lightly tanned, meso­ and metathoracic wing and metanotum darker. Setae 1–4,6,12­CT usually triple, 5­CT with 5 branches, 7,9,11­CT usually with 2 branches, 8,10­CT usually with 6 branches. Trumpet. Moderately tanned, cylindrical in frontal view; conical in lateral view, length 0.59–0.82 mm (mean 0.69 mm). Tracheoid area slightly darker, extending about 0.41 from base, pinna length 0.20–0.24 of trumpet length. Abdomen. Length 2.48–3.78 mm (mean 3.14 mm), lightly tanned, terga II­ VII with median tanned band, terga II­V with tiny spicules. Setae 6­I,II single, longer than 7­I,II that is usually double. Seta 1­I with 9 (5–12) primary branches and 48–60 secondary branches, 1­II with 8 (7–12) main branches, 6­III,VI always with 4 (2–4) branches, 6­VII usually double (2–5). Seta 4­VIII usually double (2, 3), 9­VIII with 6 branches (4–8), 14­ VIII usually double (1, 2). Genital lobe. Female little tanned and 0.12–0.23 mm (mean 0.18 mm), darker in male and 0.35–0.40 mm (mean 0.38 mm). Paddle: 0.85–1.04 mm, translucent, without spicules, midrib distinct except at apex, seta 2­P about 0.35 length of 1­P.

LARVA (fourth instar) ( Fig. 2): Setae as figured, range and mode of setal branches given in Table 2. Head. Wider than long, lightly tanned, lateralia and dorsal apotome tanned. Dorsomentum with 6 (6, 7) teeth on both sides of median tooth. Seta 2­C absent, 1­ C not tanned, 4­C single, long, 5,7­C aciculate strongly developed, 8­C usually with 3 branches, 9­C usually with 6 branches, 10­C with 1, 2 branches, 11,12­C usually with 4 branches, 13­C with 2–6 branches, 14­C single, 15­C usually with 4 branches, 16, 17­C small usually simple (1–3 branched), 6­Mx single, longer than 4­C. Collar dark. Antenna. Length 0.55–0.73 mm (mean 0.62 mm), slightly tanned with dark ring at base and tanned distal to seta 1­A, proximal part aciculate, less aciculate laterally on distal part. Seta 1­A large with 17–31 aciculate branches, inserted 0.38–0.49 from base. Thorax. Integument hyaline, smooth, tubercles of all large setae tanned, tubercles of setae 9–12 on meso­ and metathorax with small spine. Seta 0­P with 9–15 branches, setae 1,3­P single, mainly same length, 4,8­P normally double, 7­P usually with 2 branches (1,2), 11­P with 3–5 branches, others single. Seta 1­M with 2–5 branches, 3­M single, similar in length to 1­M. Setae 1­T with 3–5 branches longer, twice length of 2­T, usually double, 3­T usually with 3 branches (1–5) and similar in length to 1­T. Abdomen. Cuticle smooth, except on segment VIII around comb area. Tubercles of setae 6­I,VI, 7­I, 1,3­VIII moderately tanned. Setae 1­I with 5–12 branches, 1­II with 3–6 branches, 1­III,V­VII usually with 4 branches. Segment VIII. Comb with 36–68 scales arranged in 3 or 4 irregular rows, normally fringed. Segment X. Saddle complete, length 0.35–0.49 mm, tanned, with distinct spicules on posterolateral margin. Seta 1­X usually triple (2–5), 2­X triple, 4­X with 6 pairs of setae. Siphon. Length 1.44–2.06 mm, width 0.41–0.58 mm (measured at base), siphon index 4–6 (mean 4.7), tanned, pecten on basal 0.25, with 10–14 spines with 1 (1,2) basal denticles on one side. Seta 1­S in 5 pairs, 1a­S inserted near distal pecten spine, 1d­S out of line, 1a,c­S usually with 4 branches, 1d,e­S usually with 3 branches.

a Based on counts from 10 specimens.

b Range (mode).

c Number of primary branches.

Material examined

2 ♂, 11 ♀, 13 Pe, 15 L, 4 Le, 14 L (third and second instars) as follows: Argentina, Mendoza, Potrerillos , Mendoza River , 32º56’59’’ E, 69º11’49’’ S, 1353 masl, M.C. Dominguez & E. Scheibler coll. , 2 ♂, 2 ♀, 1 Pe, 2 L, Feb. 2002. Same locality and collectors, 9 ♀, 12 Pe, 13 L, 4 Le, 14 L (third and second instars), Apr. 28, 2004.

a Based on counts from 10 specimens.

b Range (mode).

Distribution

Culex cuyanus is known only from San Juan, La Rioja, and Mendoza Provinces, Argentina .

Bionomics

Larvae were collected from puddles and pools of water, with sparse or no grasses and aquatic macrophytes, derived from the Mendoza River. Larvae were found in association with larvae of Anopheles annulipalpis Lynch Arribalzaga and other macro­invertebrates such as Aeshnidae (Odonata) , Chironomidae (Diptera) , Corixidae (Hemiptera) , Hyallelidae (Crustacea), and Hydrophilidae (Coleoptera) . The pools had a maximum depth of 0. 5 m. Water temperature was 16º C (April) and 20.7 ºC (February), pH 6.77 (April) and 7.57 (February), dissolved oxygen concentration 1.7 mg L ­1 (April) and 4.3 mg L ­1 (February), percent oxygen saturation 21% (April) and 56% (February), and electrical conductivity 950 µS cm ­1 (April) and 1170 µS cm ­1 (February).

Diagnosis

Duret (1968) in his description of this species compared it with Cx. lygurus Root, from which he differentiated it by the absence of a ring of white scales on the tarsi, the pale spot on the proboscis, and the distinct genitalia, as well as the differences in habitat. Culex cuyanus can be separated from other members of the subgenus by the male genitalia. The phallosome has a lateral plate with 3–5 small teeth, and the lateral lobe is flat and continuous with the base of the thumblike dorsal process and bluntly rounded. The ventral arm is straight, pointed, and longer than the teeth of the median process; the dorsal arm is long and strong, resembling a lamina. The female is similar to the male; however it is difficult to separate from other females of Culex. The presence of pale scales at the base of the costa in adults, and on the male wing, is characteristic of six species of Culex in South America, including Cx. apicinus Phillipi; Cx. brethesi Dyar; Cx. fernandezi Casal, García & Cavallieri; Cx. lahillei Bachman & Casal; Cx. maxi Dyar; and Cx. paramaxi Duret. The scales of the postgena are broad compared with the scales of Cx. pipiens L., and resemble those of the Spissipes Section of Cx. (Melanoconion). The pupae are similar to other pupae of Culex (Culex) species and no characters are available for their identification. The larvae are similar to those of many Culex (Culex) species. However, they can be identified by the presence of seta 16,17­C on the collar area, a characteristic that is not frequent in other Culex (Culex) species ( Harbach & Knight 1980). Larvae of this species can be distinguished from those of the Dolosus Complex by the length of setae 1­M and 1­T.