Culex (Melanoconion) bahiensis Duret, 1969

Lestani, Eduardo A. & Rossi, Gustavo C., 2012, Description of the female, pupa, and larva of Culex (Melanoconion) bahiensis Duret, and redescription of the male (Diptera: Culicidae), Zootaxa 3323, pp. 57-63 : 58-63

Culex (Melanoconion) bahiensis Duret, 1969 , M, MG*

FEMALE. Small mosquito with dark brownish scales. Head: Antenna dark, length 1.6 – 1.7 mm. Maxillary palpus dark-scaled, length 0.25 mm. Vertex with narrow decumbent scales from the coronal suture to the posterolateral area; broad spatulate scales, these grey laterally and dorsally, restricted to sides of eyes; forked scales brown. Proboscis dark-scaled, labella slightly pale, length 1.6–1.7 mm. Cibarial armature: Cibarial bar broad, concave; Cibarial teeth as figured ( Fig. 1 A ). Thorax: Integument dark brown. Scutum with fine falcate scales with pale golden reflections, except on lateral scutal fossa, anterior promontory and lateral prescutellar area where the scales are whitish. Complete row of dorsocentral setae, strong, black; acrostichal setae absent. Median lobe of scutellum with whitish falcate scales, lateral lobes with few scales of the same type. Scutellar scales whitish, with 3 or 4 long and 3 short setae on each lateral lobe and 6 long and 4 short ones on midlobe. Pleura concolorous with scutum. Small spots of whitish scales only on upper mesokatepisternum, mixed with setae on lower mesokatepisternum. Postpronotum with few scales, with 3 dark setae on posterodorsal margin. Few whitish scales on lower prealar area and 7 whitish scales on lower mesokatepisternum. Pleural setae as follows: 8–10 antepronotal, 7 or 8 upper proepisternal, 4–6 prealar, 6 or 7 lower mesokatepisternal and 1 lower mesepimeral. Wing (n=2): Length 3.12–3.20 mm, vein R 2 0.85–0.87 mm, vein R3 0.45–0.50 mm. Halter: Scabellum and ventral portion of pedicel pale. Capitellum and dorsal portion of pedicel dark. Legs: Anterior surface of coxa darker, yellowish posteriorly. Fore- and midcoxae with row of dark scales anteriorly. Femora mainly dark-scaled; fore- and midfemora whitish on posterior surfaces diluted toward apex; hindfemur with whitish ventral surface. Tibiae dark-scaled; tarsi dark-scaled, tarsomeres with basal rings of translucent brown scales. Abdomen: Tergum II dark-scaled dorsally, with pale basolateral spots, terga III–VI dark-scaled, dorsally with broad basal pale band joined to basolateral spots, terga VII and VIII dark-scaled dorsally, with pale basolateral spots. Sterna II–VII with basal band of cream-colored scales. Abdominal setae golden.

MALE: Like female except for sexual and following differences. Antenna strongly verticillate, length 1.5–1.8 mm (mean = 1.63 mm). Proboscis dark-scaled, length 1.6–2.0 mm (mean 1.81 mm), false joint about 0.6 from base. Maxillary palpus dark-scaled, length 2.2–2.6 mm (mean = 2.4 mm), extending beyond apex of proboscis from middle of penultimate palpomere. Vertex with yellowish forked scales. Thorax: Integument brownish, with sparse whitish falcate scales of uniform size and color except whitish on anterior and lateral margins. Abdomen: Tergum II dark or with few white scales on basolateral areas, III–VI with broad basal bands of white scales joined to basolateral spots, VII and VIII with basolateral pale spots that sometimes join in middle. Sterna dark-scaled, sterna II–VII with broad basal bands of white scales, sternum VIII dark-scaled. Genitalia ( Figs. 1 B, 2): Gonocoxite conical, mesal side concave, inner side slightly convex; ventrolateral setae strongly developed, mesal surface with short, sparse setae. Subapical lobe with 2 divisions. Proximal division scarcely longer than distal, with arm as long as 2 setae (a, b); both setae sinuous apically, basal seta shorter (83.5 µm) than distal (86.8 µm). Distal division ending in 2 short arms, basal division with long apically hooked seta (h,), 1 short and 1 long and flat saber-like seta (s) and 1 narrow lanceolate flat seta (l). Distal arm curved, with 4 narrow appressed flat setae (f) of nearly same length; a slender seta born at middle of distal division of subapical lobe. Gonostylus: Slender, curved and widened distally on lateral side, with 2 setae, and conspicuous saw blade-like subapical crest before apical snout; gonostylar claw short, broad. Phallosome: Aedeagal sclerite narrow, slightly curved. Lateral plate with apical process bifurcate at tip, long, narrow, projecting caudally, ventral process basal in position, upper point of tip pointed and slightly curved. Tergum IX: Lobes ovoid, with short setae except laterally.

PUPA ( Fig. 2 ): Chaetotaxy as figured; range and modal number of branches in Table 1. Cephalothorax: Lightly and unevenly tanned, legs and metathorax darker. Setae 1–3-CT usually with 2 (1,2) branches; 5-CT double; 4,6,7,9,11-CT always single; 8-CT double, rarely triple, 10-CT usually with 4 (3–6) branches, 11,12-CT similar, 11-CT stronger, 12-CT usually single (1,2). Trumpet: Moderately tanned, slender, nearly cylindrical, length 0.51–0.59 mm (mean = 0.56 mm), index 8.3–9.2 (mean 8.6 mm), pinna 0.09–0.12 mm (mean 0.1 mm), meatus with short slit. Abdomen: Lightly tanned, anterior margin of terga II–IV darker, length 2.20–2.60 mm (mean = 2.37 mm). Setae 1-II–VII multiple, of same length except 1-VII shorter; 3-II,VI,VII single, 3-III usually single (1–3), 3- IV usually triple (1–3), 3-V single, occasionally double. Paddle: Lightly tanned, length 0.68–0.78 mm (mean 0.72 mm), width 0.38–0.46 mm (mean = 0.41 mm), midrib and buttress smooth, midrib incomplete apically, buttress developed only at base, margins smooth. Setae 1,2-P single, 2-P 0.3 length of 1-P.

LARVA ( Fig. 3 ): Chaetotaxy as figured; range and modal number of branches in Table 2. Head: Wider than long, length 0.62–0.65 mm (mean 0.63 mm), width 1.0– 1.1 mm (mean= 1.05 mm) when measured without coverslip and length 0.77–0.87 and width 1.00–1.20 when examined with coverslip. Moderately tanned, posterior part of dorsal apotome and area behind compound eye lightly tanned. Median labral plate with concave margin between insertions of seta 1-C. Hypostomal suture complete, collar poorly developed, tanned. Dorsomentum usually with 6 teeth on either side of broad median tooth. Seta 1-C spiniform, dark; 2,3-C absent; 4-C short, single; 5-C usually double (1–3); 6-C long, single; 9–10-C similar in length; 8,9-C branched, 8-C shorter than 9-C; 11-C triple; 12-C usually double (2–4); 13-C usually triple (2,3). Antenna: Length 0.61–0.65 mm (mean 0.63 mm), tanned, with conspicuous spicules, distal part aciculate laterally. Seta 1-A inserted 0.68 from base (0.66–0.75), with 24 (22–26) branches. Thorax: Integument hyaline, covered with spicules (10 µm) on dorsal and ventral surfaces, large setae 1–3-P and 9–12-P,M,T inserted on common tubercles; seta 1-P usually single (1–4), 2-P single, very long; 3-P about 0.15 length of 1,2-P, usually with 3 (1–4) branches; 4,7-P usually double (1,2 and 1–3, respectively); 8-P usually single (1,2). Seta 1-M usually double (1–4); 2-M single. Seta 13-T usually triple (3,4). Abdomen: Integument hyaline, with shorter spicules (approximately 5 µm) than those on thorax on both sides; seta 6-I–VI double but 6-III occasionally triple; 7-II–VI usually 4- or 5-branched. Segment VIII: Comb with 49–62 moderately long scales, scales fringed on sides and apex, apical fringe distinct, lateral fringe inconspicuous, scales arranged in 3 or 4 irregular rows. Siphon: Length 1.2–1.3 mm (mean = 1.24), index 6.3–7.6 (mean = 7, width measured at base), pecten with 13–21 spines (mean = 16) increasing in size from base, ventral edge of spines with complete row of close-set denticles. Seta 1-S in 7 pairs, 5 posterolateral pairs with 2–5 branches and nearly twice as long as width of siphon at point of insertion; dorsolateral pairs with 1 or 2 short branches; seta 2-S hooked, inserted in membrane, bent ventrally with slender curved submedian accessory branch. Segment X: Saddle complete, with small spines forming a conspicuous spot and 7 spines extending beyond caudal border, length 0.31–0.35 mm (mean 0.32), siphon-saddle index 3.5–3.9 (mean 3.7). Seta 1-X usually triple (2–4); 2-X with one long and one short branch; 3-X long, single; 4-X usually in 6 pairs, 4a-X usually with 6 branches, most anterior seta triple. Anal papillae long, approximately twice saddle length.

Diagnosis. Culex bahiensis is presently assigned to the Distinguendus Group of the Melanoconion Section of Sirivanakarn (1983). The species is readily identified as a member of the Putumayensis Subgroup of the Distinguendus Group by means of Sirivanakarn's key for the male genitalia.

The choice of which subgroup the species should be placed in, however, is difficult. According to Sirivanakarn's key to females, and because of the presence of a patch of scales on the upper corner of the mesokatepisternum, the species should be included in the Distinguendus Subgroup. Sirivanakarn's key separates pupae of the Distinguendus and Putumayensis Subgroups according to seta 9-VIII with either 4 or 5,6 branches, but Cx. bahiensis has only two branches.

Siphon length of 1.5–2.0 mm is used in Sirivanakarn's key to separate larvae of two of the five subgroups of the Distinguendus Group. These are the Distinguendus and Putumayensis Subgroups. Since the siphon of Cx. bahiensis is 1.2–1.3 mm in length, the species does not belong to the Distinguendus Subgroup. In contrast, because larvae of the Putumayensis Subgroup are distinguished from those of the Distinguendus Subgroup by the length of the seta 1-S, which is greater than the width of the siphon at the point of insertion, Cx. bahiensis should be placed in the Putumayensis Subgroup. Moreover, seta 7-I is double in Cx. bahiensis .

The larva of Cx. bahiensis differs from that of Cx. putumayensis in having seta 4-C single and conspicuous as opposed to multiple and small as in Cx. putumayensis ; setae 11–13-C have 2 or 3 branches instead of multiple branches as in Cx. putumayensis ; setae 5,7-M are simple in Cx. bahiensis whereas 5,7-M are spiculose in Cx. putumayensis ; and finally 49–62 comb scales are present on segment VIII instead of 41–45 as in Cx. putumayensis .

Seta 6-CT of the pupa of Cx. bahiensis is single, but that of Cx. putumayensis usually has 6 branches; seta 10- CT has 3 or 4 branches as opposed to 14–16 branches in Cx. putumayensis ; seta 9-VII is single whereas it has 3 branches in Cx. putumayensis ; and finally, seta 9-VIII is double, not triple as in Cx. putumayensis .

The female of the Cx. bahiensis has a patch of scales on the upper corner of the mesokatepisternum, which is absent in Cx. putumayensis and Cx. distinguendus . Because the female, pupa, and larva of Cx. bahiensis have features common to both subgroups ( Distinguendus and Putumayensis ), the question of the taxonomic placement of this species requires further investigation.

Material examined. Eleven larvae and 5 pupae were collected in a puddle located 50 m from the Salto Arrechea waterfall and approximately 200 m from the Iguazú River (25º 39' 18.51'' S; 54º 27' 26.61'' W). The following specimens were obtained from rearing: 5 M, 3 MG, 2 F, 6 Pe, 2 Le, 9 L.

Bionomics. All specimens examined were collected as larvae and pupae from a puddle formed by rain on basalt soil. The puddle was in a shadowy under story of native forest that is usually very humid due to a small waterfall nearby. The larvae were found in association with Ochlerotatus crinifer (Theobald) , Ochlerotatus serratus (Theobald) , and Cx. dolosus (Lynch Arribálzaga) .

Figures

FIGURE 2. Pupa and male genitalia of Culex (Mel.) bahiensis Duret. AeS = Aedeagus, CT = cephalothorax, dSL = distal division of subapical lobe, GC = gonocoxite, GL = genital lobe, Gs = gonostylus, LP = lateral plate, Pa = paddle, pSL = proximal division of subapical lobe, T = trumpet, I – IX = abdominal segments, IX-Te = tergum IX (Number of setae is only illustrative). Scales in mm.

FIGURE 3. Larva of Culex (Mel.) bahiensis. A = antenna, C = cranium; CS = comb scales, Dm = dorsomentum, M = mesothorax, P = prothorax, PS = pecten spines, S = siphon, T = metathorax, I – VIII, X = abdominal segments. Number of setae is only illustrative. Scales in mm.

FIGURE 1. A: Cibarium of female; B: subapical lobe and gonostylus of male genitalia.