Culex (Culex) brethesi Dyar, 1919

Rossi & C, Gustavo, 2006, Redescription of Culex (Culex) brethesi Dyar, 1919 (Diptera: Culicidae), Zootaxa 1312, pp. 25-35 : 26-34

Culex (Culex) brethesi Dyar, 1919

Previous usage: Culex lynchii Bréthès, 1912 , female; Bréthès, 1916, male (not female); Bachmann & Casal, 1962, male, larva, pupa; in part of Bram, 1967.

Culex (Culex) brethesi of Dyar, 1928, male, female.

Culex (Culex) inflictus in part of Lane, 1953.

FEMALE: (Range of branches based on 8 reared females). Head: integument dark brown. Vertex and occiput with narrow, curved decumbent pearly scales medially, broader and whitish laterally and denser, forked scales black. Clypeus dark brown, bare. Proboscis longer than forefemur, dark­scaled but scales on underside paler from near base to distal 0.2. Maxillary palpus 0.17 length of proboscis, palpomere 3 dark­scaled. Antenna subequal to proboscis in length, pedicel brown. Thorax: scutal integument dark brown, setae dark. Scutal scales small, fine, golden, somewhat larger on scutal fossa and supraalar areas. Scutellar integument moderate brown. Scutellar setae strong, long, 8 on mid lobe and 6 each in lateral lobe. Scutellar scales same as scutal fossal scales. Paratergite bare. Antepronotum: light brown, 8–10 large setae, 2–5 small setae and few scales. Pleural integument whitish. Pleural setae dark, numbers as follows: 12 (9–15) proepisternal, 2–4 prealar, 2 upper mesokatepisternal, 2–5 lower mesokatepisternal, 1 prominent lower mesepimeral, 9–12 upper mesepimeral. Pleural scales in whitish patches on lower and upper mesokatepisternal and small patch before upper mesepimeral setae. Without prealar and postspiracular scales. Legs: coxae and trochanters with scales on lateral surface. Femora darkscaled except for line of light scales on anterior surface from base to near apex; tibiae dark­scaled with white scales at apex and base; tarsi dark­scaled. Wings: darkscaled, costa with pale scales from base to level of humeral crossvein. Halter: stem light, apex and knob dark­scaled. Abdomen: terga mainly black­scaled; tergum I setose, without scales; terga II, VIII with traces of basal white bands, with posterolateral triangular patch of white scales extending basally, these spots united to inconspicuous basal pale bands when present. Sternum II with white scales, III to VIII with dark scales and median and posterior patches of white scales.

MALE: Holotype male mounted on a microscope slide with a female, labeled: " Culex Lynchii Brethes " (handwritten in ink) and “Holotipo Culex (Culex) brethesi 364, Dyar, 1919; 1966 Casal” (handwritten in pencil). On the other side: “ Holotypus ” and “Dipt. 62” on separate labels. This information appears in Belkin et al. (1968). The holotype is deposited in the Buenos Aires Museum ( Fig. 2 a, b, c). Head: as described for female except for sexual differences. Proboscis dark­scaled except from base to apex ventrally. Maxillary palpus exceeding length of proboscis by length of two distal palpomeres; bases of palpomeres 3, 4 and 5 and apices of 3 and 5 with spot of white scales, and 4 with small line apically. Abdomen: terga with traces of narrow basal white bands, basolateral spots distinct. Genitalia (Fig. 1): Ninth tergal lobes small, each with 9–19 setae in 2 or 3 irregular rows (Fig. 3 d). Gonocoxite (Fig. 1 a, b, Fig. 2 c) normal, with 10­16 strongly developed ventrolateral setae. Subapical lobe undivided, gonostylus stout, curved and narrowed distally, with 2 small slender setae near apex of concave surface. Gonostylar claw short, trough­like. Subapical lobe of gonostylus prominent, undivided, setae a–c and g in row on apex, setae f and h at level of g on mesal and lateral sides of lobe respectively, setae a rod­like and pointed, b and c with hooked apices, g foliform, asymmetrical, f short, and h slightly curved distally. Phallosome (Fig. 1 c, d, e, Fig. 3 c): lateral plate small with 1­3 small teeth, small lateral lobe flat, continuous with base of thumb­like dorsal process. Ventral arm straight dorsomesad, dorsal surface somewhat convex, longer than teeth, dorsal arm V­shaped medially. Paraproct with long, curved basal lateral arm and conspicuous ventral acetabulum, with lobe­like appearance near paraproct crown, crown dark with numerous needle­like spicules, basal lateral arm with 2–5 cercal setae. Seta f of the holotype is very short. In 10 of 36 male genitalia examined, seta f was minute ( Fig. 2 c), in 14 other it was represented by one alveolus and in another 12 it was not visible.

PUPA: Placement and character of setae as in Fig. 3, range and modal number of branches in Table 1. Cephalothorax: Lightly tanned, metanotum and legs darker, setae 1,2­ 9­CT usually triple, 3,5­12­CT usually with 4 branches, 10­CT usually with 9 branches (4–11), 11­CT usually double (90%) (2,3). Trumpet: tanned, almost cylindrical, index 5.50 (4.18–6.43) tracheoid area darker, about 0.3 from base. Abdomen: lightly tanned, posterior area of tergum I and anterior margin of other terga darker, particularly terga II­VII; length about 3.3 mm. Seta 1­I with 6–8 primary branches, 1­II with 9–20 branches, 1­III usually 6 branches, setae 2­I, 10­IV, 11­V,VII and 7­VII usually single (90%). Genital lobe: lightly tanned in both sexes, length 0.20 mm in female, 0.39 mm in male. Paddle: lightly tanned, midrib distinct except at apex; 2 setae present 1­Pa larger, single or double with distinct alveolus, 2­Pa shorter, single, without distinct alveolus. The positions of these setae relative to each other are quite variable.

TABLE 1. Number of branches for pupal setae of Culex (Culex) brethesi Dyar a.

a Based on counts from 10 specimens. b Number of primary branches Mode in parenthesis.

LARVA: Placement and character of setae as in Fig 4 , range and modal number of branches in Table 2. Head: lightly tanned, darker areas of antennal prominence, compound eye and dorsal apotome. Collar moderately developed along lateralia, tanned. Dorsomentum with 5–7 teeth on either side of median tooth. Seta 1­C slender, 2­C absent, 3,4­C single, 5­7­C strongly developed, 5­C usually 5 branched (3–7), 6­C usually triple (3–6), 7­C with 5–10 branches. Antenna: length 0.64–0.74 mm, range 0.66 mm. lightly tanned, darker distally; seta 1­A with 18–28 (mode 21) aciculate branches. Thorax: integument hyaline, covered with tiny spicules (near 5 µm), tubercles of all large setae tanned, tubercles of setae 9­12­P, M with moderately large spine. Setae 1­3, 6­P single, 4,7­P double, 8­P usually with 1­4 branches, 11­P with 3–5 branches. Seta 1­M usually with 1–5 branches, larger than 3­M; 3­M usually single. Setae 1,2­T of similar length.

Abdomen: integument hyaline, spiculation present but finer than on thorax, more evident on segment VIII. Tubercles of setae 6­I,VI, 7­I and 1­ 3 ­VIII moderately tanned. Seta 1­II­ VI double, 1­I with 5–11 branches. Segment VIII: comb with 34–44 scales arranged in 3 or 4 irregular rows, scales normally fringed on sides and apex. Seta 1­VIII with 7–9 branches, 3­VIII with 8–12 branches, 5­VIII with 3–7 branches. Siphon: tanned; pecten on basal 0.3 of siphon, with 11–17 large scales each with 1­3 basal denticles; index 3.79–4.91, mean 4.35. Seta 1­S in six pairs, 1a­S inserted near most distal pecten spine, 1e­S out of line. Segment X: saddle complete, tanned, with distinct spicules on posterolateral end; length 0.44–0.50 mm, range 0.46 mm. Seta 1­X usually double (2,3), 2­X usually double (2,3), ventral brush (seta 4­X) with 6 pairs of setae.

Male genitalia structures of Culex brethesi . a, b: Gonocoxite; c: Lateral plate in dorsal

view; d: Lateral plate in ventral view; e: Lateral plate of the holotype of Cx. brethesi .

Pupa of Culex brethesi . a): Cephalothorax, CT; b): Metathorax and abdomen, left side = dorsal, right side = ventral; and male genitalia structures of Cx. brethesi ; c): Lateral plate of genitalia; d): Ninth tergum of genitalia.

Material examined: Culex brethesi : 40 ♂, 41 ♂ G, 30 Ψ, 45 Pe, 8 P, 25 Le, 9 L, as follows: Argentina: Buenos Aires Province, San Isidro 1 ♂ holotype Bréthès leg. MACN; Zarate 3­X­1998, 12 ♂, 12 ♂ G, 5 Ψ, 8 Pe, 2 L, 13 Le, Spinelli leg.; same locality Route 9 km 109 3­III­2004, 1 ♂, 1 ♂ G, 5 Ψ, 6 Pe, 4 Le Rossi leg.; Tandil, Airport, 13­X­2001 1 ♂, 1 ♂ G, G. Marti leg.; Brandzen, Route 215 km, 25, 22 ­III­1989, 1 ♂, 1 ♂ G, G a r c ίa­Rossi leg.; La Plata, City Bell, 27­IX­1987, 7 ♂, 7 ♂ G, 2 Pe, 1 Le, Rossi leg.; La Plata, Romero, April, 1996, 3 Ψ, 2 Pe, 6 Le; 24­V­1996, 1 Pe, 2 L, 2 Le; Jun., 1996, 1 ♂, 1♂ G, 1 Pe, 1 Le; 17­VIII­2001, 1 ♂, 1 ♂ G, 1 Pe, 1 Le; 26­VIII­2001, 2 ♂, 2 ♂ G, 2 Pe, 1 L, 4 Le, all J. J. Garcia leg.; idem, 2 ♂, 2♂ G, 3 Ψ, 5 Pe, 5 Le, 6­VII­2005; idem, 2 ♂, 2 ♂ G, 6 Ψ, 12 Pe, 9 Le, 2 L, 28­IV­2005, all V. Micieli leg.; Ensenada, Punta Lara, Boca Cerrada, 25­IX­1989, 4 ♂, 4 ♂ G, 4 Ψ, 3 Pe, 2 L, Campos­Maciá leg. Entre Rίos Province, Chajari, Camping Drewars, 1 ♂ G, 1 Ψ, 1 Pe, R. Ronderos leg.; Corrientes Province, Villa Olivari, 16­VIII­ 1995, with CDC light trap, 2 ♂, 2 ♂ G, Rossi leg.; Posadas, Misiones Province, 3 ♂, 3 ♂ G, 3 Pe, Rossi leg. All specimens are deposited in the La Plata Museum.

Comments: The positions of the paddle setae are variable, as shown in Fig.3b. Tanaka (2004) made a similar observation for species of Culex from Japan. Tanaka designed the longer seta with an alveolus as seta 1­Pd and the shorter one without a visible alveolus as seta 2­Pd. In this work these setae are designated setae 1­Pa and 2­Pa, respectively, in accordance with more recent workers.

Distribution: Culex brethesi is known from the provinces of Buenos Aires, Cordoba, Mendoza, Misiones, Santa Fe and Santiago del Estero, all confirmed by dissection of male genitalia ( Bachmann & Casal, 1962), Entre Rios Province ( Rossi, 1995), Corrientes Province ( Rossi et al., 2002), and Misiones Province (this report). Other records of this species not based on dissected male genitalia are dubious.

Systematics: Culex brethesi larvae were collected in ponds or pools with or without grass. In some specimens were collected in association with larvae of Cx. dolosus and Cx. maxi Dyar, 1928 . The presence of pale scales at the base of the costa in adults of Cx. brethesi is a characteristic of several species in South America, including Cx. apicinus Phillipi, 1865 , Cx. fernandezi Casal , Garcίa & Cavallieri, 1966, Cx. lahillei Bachman & Casal, 1962 , Cx. maxi and Cx. paramaxi Duret, 1968 . The characteristics that separate Cx. brethesi from these species include: tarsi and abdominal segments with white bands in Cx. maxi ; abdominal terga with white bands in Cx. fernandezi ; postspiracular scales in Cx. lahillei ; scutum with pattern of pale scales in Cx. apicinus ; and Cx. paramaxi is known only in the type locality. The male is distinguished by the genitalia. The reduction of the mesosome is similar to Cx. acharistus Root, 1927 , but this species has seta f hooked. The majority of pupae of the species of Culex (Culex) are extremely similar and very difficult to differentiate. The fourth­instars larva of Cx. brethesi is very similar to Cx. dolosus (s.l) and Cx. eduardoi Casal & Garcia. It is possible to distinguish Cx. dolosus by the larger spicules and smaller length of the saddle, and Cx. eduardoi by the larger siphonal index, larger number of comb scales and absence of spicules in abdominal segments I–VI.

TABLE 2. Number of branches for setae of the fouth­instar larvae of Culex (Culex) brethesi Dyar. a

Head Thorax Abdominal segments

a Based on counts from 10 specimens. Mode in parenthesis.

Figures

FIGURE 2. Holotype of Culex brethesi: a: Microscope slide bearing the holotype (the lower specimen); b: Genitalia; c: Detail of the gonocoxite.

FIGURE 4. Larva of Cx. brethesi, a): Thorax and abdominal segments I­VI; left side = dorsal, right side = ventral; b): Head; left side = dorsal, right side = ventral. Pecten (PS); comb scale (CS); c): Abdominal segments VII­X, side view.