Psorophora (Psorophora) pallescens Edwards

Stein, Marina, Laurito, Magdalena, Rossi, Gustavo Carlos & Almirón, Walter Ricardo, 2009, Morphological description of the pupa and fourth-instar larva and redescription of the adults of Psorophora (Psorophora) pallescens Edwards (Diptera: Culicidae), Zootaxa 2306, pp. 51-58 : 52-57

Psorophora (Psorophora) pallescens Edwards

Psorophora pallescens Edwards, 1922: 76 (M, F). Type locality: Paraguay (BM). Del Ponte & Castro 1952: 221 (M*, F*, tax.). Lane 1953: 737 (M*, F). Stone 1956 (1957): 337 (M*). Guedes et al. 1965: 18 (F*). Belkin 1968: 28 (lectotype desig.).

Psorophora stigmatephora Dyar, 1922: 116 (M, F*). Type locality: Río Tapenaga, Colonie Florencia, Gran Chaco, Argentina (USNM).

FEMALE: Head: Occiput with broad white scales, midline without scales, erect scales thin and pale. Torus and clypeus ochre. Maxillary palpus and proboscis with mixed yellowish, dark and shiny semi-erect scales at base, dark-scaled apically. Maxillary palpus 0.80–1.30 mm (1.10 mm). Proboscis straight, 3.00– 3.50 mm (3.10 mm), slightly longer than forefemur. Thorax: Scutal integument light brown, scutum with broad white scales. Acrostichal area with narrow golden scales, dorsocentral area with yellow to pale scales. Disc of scutum with a spot of dark semi-erect scales on anterior half and both sides of midline followed by 2 parallel stripes, which extend up to prescutellar area, separated by yellowish to pale scales. Pleura covered with broad white scales, except for lower mesokatepisternum with slender scales. Acrostichal and dorsocentral setae dark. Upper proepisternal and prealar setae golden, antealar area with strong dark setae. Pleural setae golden: 19–22 (22) proepisternal, 14–19 (17) prealar, 11–17 (15) and 6–9 (6) upper and lower mesanepimeral, respectively, 4–7 (6) and 3–8 (8) upper and lower mesokatepisternal, respectively, 2–4 (3) prespiracular and 6–9 (8) postspiracular. Scutellum with white scales confined to lobes: 20–26 (20) and 14–18 (14) large median and lateral scutellar setae. Wing: With mixed broad whitish and dark scales on posterior side of costa, subcosta and R; R2 and R3 lightly scaled; other veins predominantly dark-scaled. Basal and ventral surface of R with a spot of erect white scales. Halter : Integument pale, capitellum with white to yellowish scales. Legs: Integument light brown, fore-, mid- and hindcoxae white-scaled basally, middle region of anterior surface of fore- and midcoxae with mixed white and black scales. Fore- and midfemora basally yellowish-scaled, apically black. Hindfemur with yellowish scales on anterior 0.75, some erect at base, remainder with erect black scales. Tibia with erect yellowish scales at base, black at apex. Joints between tarsomeres with a ring of white scales, foretarsomere II with erect scales. Ungues toothed. Abdomen: Integument light brown. Terga with broad and white to yellow scales. Sterna white-scaled, black-scaled on midline.

MALE: Like female except for sexual differences. Genitalia ( Fig.1 c,d): Gonocoxite 2x longer than basal width, minutely spiculate, with long strong setae on dorsal surface, shorter and thinner ventrally. Gonostylus narrow, round basally, 0.75 length of gonocoxite, gonostylar claw small, pointed. Claspette: Divided, narrow, apical lobe with 29–31 tubercles bearing long thin setae, and external part leaflet-shaped, mesal part bent forward. Proctiger: Narrow, heavily sclerotized apically, toothed. Aedeagus: Heavily sclerotized apically, ovoid with sharp-pointed apex, with 2 lateral expansions, attenuated portion toothed. Ninth tergum with 7 conspicuous setae on each lobe.

PUPA ( Fig.1 a,b): Placement and character of setae as figured; range and modal number of branches in Table 1 . Cephalothorax: Integument light brown. Trumpet cylindrical, lightly tanned, length 0.93–1.35 mm (1.11 mm), width 0.20–0.35 mm (0.23 mm), index 3.85–5.50 (4.79); pinna 0.45–0.57 (0.50) length of trumpet; tracheoid area 0.41–0.51 (0.46) length of trumpet. Abdomen: Lightly tanned, similar to cephalothorax, with a darker median longitudinal strip. Abdominal segments II,V with 2 discontinuous (broken) thin oblique dark lines to each side. Setae 1-II-IV-V and 5-II,VI usually double and longer than corresponding segment. Minute marginal spicules present on external buttress. Genital lobe: Hyaline in both sexes. Length 0.35–0.45 mm (0.40 mm) in females and 0.52–0.58 mm (0.56 mm) in males. Paddle: Length 1.18–1.40 mm (1.30 mm), width 1.15– 1.35 mm (1.25 mm), paddle index 1.02–1.04 (1.03). Paddle ovoid, hyaline, buttress darker. Midrib evident, distinct except apically; length 0.98–1.20 mm (1.03 mm). Seta 1-Pa usually double, 2-Pa 0.16 of 1-Pa.

Seta Nº CT a Abdominal segment Paddle a CT = cephalothorax.

b For seta 1-I, five to nine branches and 25-40 secondary branches. c Not counted.

LARVA (fourth-instar) ( Fig. 2 ): Placement and character of setae as figured; range and modal number of branches in Table 2. Head: Square, slightly wider than long, width 1.75 mm, length 1.45 mm. Integument hyaline, homogeneously colored, sometimes darker laterally. Collar brown, dark, thin. Dorsomentum with dark brown teeth, basally clearer, with 7–9 (8) teeth on each side of median tooth, 2 or 3 lateral teeth longer than median tooth. Maxilla ( Fig. 2 a) of Psorophora (Psorophora) type. Seta 0-C single, 2-C absent; 3,6-C simple, 4- C long with 1,2 (1) branches, 8,9-C similar in length. Antenna: Length 0.40–0.54 mm (0.47 mm), pale and homogeneously colored, covered in stout spines. Seta 1-A 0.36–0.50 mm (0.43 mm) from base, always single, 2-6-A single, 3-A broad, with blunt apex. Thorax: Integument hyaline. Tubercles of setae 9-12-M,T with a rounded apical denticle. Seta 0–P dendritic, setae 1,5,7-P always single, 2,3-P similar in length, 6-P multiple, 0.33 length of 5-7-P, 13-P absent. Setae 3,4-M similar in length with 5–12 (9) and 4–12 (9) branches, respectively, 5,6-M always single, 10-M generally single, 11-M absent, 13,14-M dendritic. Setae 5,10-T always single, 8-T dendritic. Abdomen: Integument hyaline. Tubercles of setae 6,7-II-III pale and homogeneously colored. Seta 6-I-V generally double, 6-VI always single, seta 8-VI multiple. Segment VIII: Minutely spiculate basally. Comb with 12–18 (16) scales arranged in a row; each scale with 3–5 sharp points, median point longer than lateral ones. Segment X: Covered in minute spicules arranged in groups, increasing in size on dorsal and ventral regions. Saddle complete, length 0.70–0.89 mm (0.80 mm), light brown, siphon/saddle index 3.15–3.54 (3.35). Seta 4-X with 8 precratal setae and 4 setae on grid. Anal papillae large, tapering toward apex, papillae about 3x length of saddle, ventral papillae very slightly longer. Siphon: Length 2.32–3.12 mm (2.67 mm), wide at base 0.60–1.00 mm (0.78 mm), index 2.87–4.60 (3.48). Light yellow, intense brown basally, with rows of minute spicules, acus yellowish. Pecten on basal 0.46 with 22–33 (30) spines, spines each with 1 basal denticle, sometimes 2.

Material examined. Psorophora (Psorophora) pallescens : 6M, 6MG, 9F, 54Pe, 16Le, 4L as follows: ARGENTINA, Chaco Province: Monte Alto (27º 26’ S – 58º 55’ W), 1M, 1MG, 5F, 2Pe, 3Le, 23-X-2003; 1M, 1MG, 4F, 5Pe, 5Le, III-2004, Stein & Willener coll.; Córdoba Province: El Tío (31º 22’ S – 62º 49’ W), 4M, 4MG, 44Pe, 5Le, 16-XII-1993, Almirón coll.; La Para (30º 53’ S – 62º 58’ W), 4L, 7-II-1996 and 1Pe, 1Le, 11-IX-1997, Almirón coll.; Las Garzas (31º 10’ S – 64º 28’ W) 2Pe, 2Le, 7-II-1996, Almirón coll.

Distribution. This species is known from Argentina, Bolivia and Paraguay (Walter Reed Biosystematics Unit 2001). It is recorded from the following provinces in Argentina: Buenos Aires, Chaco, Córdoba, Corrientes, Entre Ríos, Formosa, Salta, Santa Fe, Santiago del Estero ( Campos & Maciá 1998), Mendoza ( Rossi et al. 2006), La Rioja and Jujuy ( Visintin et al. 2009).

Bionomics. Females of Psorophora pallescens were captured in horse-baited traps ( Mitchell et al. 1985); Western Equine Encephalitis virus was isolated from females of these mosquitoes ( Mitchell et al. 1987). Immature stages were collected from ground ponds, in wild and urban environments, temporary habitats with clear shallow water, grass and full sun, in association with larvae of Ps. ciliata and Ps. paulli Paterson & Shannon.

Taxonomy. Psorophora pallescens is distinguishable from other species of the subgenus ( Del Ponte & Castro 1952), which have similar size, by the light brown integument of the adults. Larvae of Ps. pallescens are very similar to those of Ps. ciliata , from which they can be separated by having setae 7,9,10,12-C branched from the base, seta 16-C present, setae 8,10-M smooth, seta 2-A 0.30 length of the antenna, seta 1-A almost at middle of the antenna and seta 8-VI multiple branched. The male genitalia exhibit the general characteristics of the subgenus, being similar to Ps. ciliata from which they differ in having the claspette filament less curved and the base of gonocoxite twice as wide as the apex ( Belkin et al. 1970). The pupa is similar to Ps. ciliata and Ps. howardii Coquillett , but differs in having seta 9-VIII and 8-CT usually double and 9-CT triple. The pupa of Ps. pallescens can also be distinguished in having two discontinuous thin oblique dark lines on both sides of abdominal segments II-V, whereas Ps. ciliata has three and Ps. howardii has a mottled appearance ( Barr & Barr 1969).

Figures

FIGURE 1. Pupa and male genitalic structures of Psorophora (Psorophora) pallescen s Edwards. a: Cephalothorax; b: Metanotum and abdomen; c: Gonocoxopodite and phallosome; d: tergum IX. Ae = aedeagus; BP = basal piece; CF = claspette filament; Cl = claspette; Gc = gonocoxite; GC = gonostylar claw; GL = genital lobe; Gs = gonostylus; MK = median keel; Mtn = metanotum; Pa = paddle; Par = paramere; Ppr = paraproct; T = trumpet; I-VIII = abdominal segments.

FIGURE 2. Larva of Psorophora (Psorophora) pallescens Edwards. a: Head; b: Thorax and abdominal segments I-VI; c: Abdominal segments VII-X. A = antenna; C = cranium; CS = comb scales; DM = dorsomentum; LPB = lateral palatal brush; M = mesothorax; Mx = Maxilla; MxB = maxillary brush; MxP = maxillary palpus; P = prothorax; PS = pecten spine; S = siphon; T = metathorax; I-X = abdominal segments.

Tables

TABLE 1. Number of branches for pupal setae of Psorophora (Psorophora) pallescens Edwards (54 specimens, modes in parentheses).

		I	II	III	IV	V	VI	VII	VIII
0	-	-	1	1	1	1	1	1	1 -
1	1–3(2)	-b	1–5(2)	2–6(4)	2,3(2)	2,3(2)	1–3(1)	1–4(3)	- 1–4(2)
2	1–4(3)	1–3(2)	1,2(1)	1,2(1)	1,2(1)	1,2(1)	2–7(3)	1,2(1)	- 1
3	1–4(2)	1–7(3)	1–5(1)	1–5(3)	3–9(3)	2–5(3)	1–3(1)	1–3(2)	- -
4	2–6(4)	c	c	1–4(3)	2–5(3)	2–11(6)	2–6(3)	1–5(3)	1–3(2) -
5	1–5(5)	2–5(4)	1–3(2)	1–5(2)	1–3(2)	2	2–4(2)	2–6(2)	- -
6	2–5(3)	1–5(3)	2–5(2)	2,3(3)	2,3(2)	2,3(2)	2,3(2)	6–11(9)	- -
7	1–3(3)	2–7(3)	1–5(3)	3–10(3)	2-8(6)	3–9(4)	1–3(1)	1–3(2)	- -
8	1–3(1)	-	-	1–6(2)	1-4(1)	1–4(3)	4–8(4)	7	- -
9	1–4(2)	1–3(1)	1–3(1)	1	1	1	1	2–9(7)	2–6(5) -
10	2–9(4)	-	-	1–5(2)	2-5(3)	1–3(1)	1,2(1)	1–3(1)	- -
11	1	-	-	1–7(3)	1-5(2)	2–6(4)	1–5(3)	1–4(3)	- -
12	1–4(2)	-	-	-	-	-	-	-	- -
13	-	-	-	-	-	-	-	-	- -
14	-	-	-	1	1	1	1	1	1 -