Culex (Culex) apicinus Philippi, 1865

Rossi, Gustavo Carlos, Laurito, Magdalena & Almirón, Walter Ricardo, 2008, Morphological description of the pupa and redescription of the adults and larva of Culex (Culex) apicinus Philippi (Diptera: Culicidae), Zootaxa 1941 (1), pp. 31-42 : 32-41

Culex (Culex) apicinus Philippi

Culex (Culex) apicinus Philippi, 1865 . (asterisk means drawings are available)

Culex apicinus Philippi, 1865: 596 (A). Type locality: Santiago, Chile. Type non existent, Belkin et al. 1968. Dyar 1928: 360 as Culex (Phalangomyia) (M*, F, L*). Edwards 1932: 206 as Culex (Culex) . Lane 1953: 341 (M*, F, L*). Forattini 1965: 143 (M*, F). Bram 1967: 26 (M*, F, L; syn).

Phalangomyia debilis Dyar & Knab 1914: 58 (M*, F; Phalangomyia ). Type locality: Matucana, (Lima), Perú (USNM). Dyar 1926: 42 as Culex (Phalangomyia) . Dyar 1928: 359 (M*, F, L*). Edwards 1930: 107 and 1932: 206 (syn. with apicinus Philippi as Culex (Culex) .

Culex escomeli Brèthes 1920: 41 (M*, F). Type locality: Arequipa, Perú (BA). Dyar 1926: 42 as Culex (Phalangomyia) . Dyar 1928: 359 (M*, F, L*). Edwards 1930: 107 and 1932: 206 (syn. with apicinus Philippi as Culex (Culex) .

Culex (Phalangomyia) alticola Martini 1931: 216 (A). Type locality: Serrata, 2,300 m, Bolivia (BM). Lane 1953: 341 (M*, F, L; syn. with apicinus Philippi ). Stone 1956 (1957): 340 (M*). Belkin 1968: 12 (tax.). Bram 1967: 26.

FEMALE: Head: Occiput with decumbent whitish scales, narrow and curved, broad decumbent white scales lengthwise ocular line and posterior margin of occiput, erect scales dark brown, sometimes yellowish scaled near midline. Ocular seta brown and interocular brown or golden. Antenna 1.68-2.08 mm (1.91 mm), pedicel homogeneously colored with pruinosity on surface. Flagellomeres dark, Flm1 with decumbent white scales except on the outer side. Clypeus dark brown with golden sheen. Labial basal setae golden. Proboscis 2.28– 2.78 mm (2.54 mm), golden scaled, 0.3 distal ventrally dark scaled. Maxillary palpus 0.37–0.39 mm (0.38 mm), dark brown scaled, 0.25 distal golden scaled, fourth palpomere vestigial. Thorax: scutum integument dark brown. Covered by narrow pale scales except by two thin denuded stripes between achrostical and dorsocentral areas, extending to 0.75 of scutum, narrow bronze scales between achrostical setae. Scutal fossa and supralar area with narrow scales that not cover uniformly the surface (scattered), bronze and pale, respectively. Anterior promontory white scaled. Prescutelar area without scales. Achrostical, dorsocentral and supralar setae dark brown. Pleural integument brown, velvety aspect, margin of each tergite pale. Spots of broad pale scales as follows: upper and lower mesokatepisternal, upper and anterior mesanepimeral and lower proepisternal. Antepronotum integument brownish with scattered, pale scales, wide intermediate between narrow occipital scales and broad scales of ocular line; mainly with golden setae, sometimes with strong dark brown setae. Postpronotum with 3–5 (4) golden setae, scales wide as in antepronotum, pale to dorsal; remain- der of pleural setae yellow to golden: 4 proepisternal, 4–7 (4) prealar, 5–6 (5) and 4–5 (4) upper and lower mesokatepisternal, respectively, 6–11 (7) and 1–2 (2) upper and lower mesanepimeral, respectively. Pre- and postspiracular setae absent. Scutellum with pale scales confined to the lobes, wide as in antepronotum; 7–8 (7) and 5–7 (5) median and lateral large scutellar setae, brown with golden sheen. Mediotergite brownish, without setae or scales. Wing: Length 3.82–4.88 mm (4.39 mm), narrow brown scaled, darker on Costa and Radius, broader pale scales at base until humeral crossvein, with sparse and equidistant white decumbent narrow scales along Costa, and forming a spot at apex of wing from Costa to vein M 3+4 over the cells SC, R1, R2, R3, and M 3+4, other veins with sparse decumbent white scales. Halter: Homogeneously yellow to tan or capitellum darker; capitellum with grey scales. Legs: Coxal integument yellowish to tan. Anterior region of fore and midcoxa pale scaled; hindcoxa pale scaled in mid region. Golden setae as follows: Forecoxa, between pale scales and ventro-posterior region; midcoxa, laterally; hindcoxa, longitudinal line posteriorly and ventro-medial region. Trochanters, bronze integument with ventral dark brown spot. Fore, mid and hindtrochanters pale scaled on posterior and ventral region and laterally in hindtrochanter. Golden weak setae, ventrally. Femora brown scaled dorsally and pale scaled ventrally, golden scaled ring on distal extreme, Fe-1 2.25–3.00 mm (2.54 mm), Fe-2 2.25-2.95 mm (2.54 mm), Fe-3 2.45–3.15 mm (2.75 mm). Tibiae golden scaled apically. Fore and midtibia dark scaled dorsally and pale scaled ventrally; hindtibia entirely dark scaled. Ti-1 1.95–3.05 mm (2.75 mm), Ta-1-I 1.00– 1.80 mm (1.62 mm), Ta-2-5-I 1.00– 1.80 mm (1.51 mm). Tarsi dark scaled; joints between tarsomeres dark scaled, sometimes few golden scales never as a ring. Pulvillus pale; unguis dark and simple. Abdomen: Integument tan to brown. Tergum I with a spot of pale scales in medioapical region, golden setae. Terga II-VII dark brown scaled with a complete basal band of pale scales in following proportions: II-Te 0.48, III-Te 0.44, IV-Te 0.48, V-Te 0.49, VI-Te 0.54 and VII-Te 0.58. Tergum VIII golden scaled, complete basal band of pale scales 0.71 of segment. Sternum pale scaled, golden setae on apical margin; IV-VI-S sometimes dark scaled distally. Genitalia ( Fig. 1 ): Cerci long, near 210 µm, cover by the tergum, postgenital plate long and not very wide (80x 125 µm), insula normal, upper and lower vaginal lip hardly chitinized.

MALE: Smaller than female, otherwise like female except as follows. Head: Erect scales of vertex yellowish, sometimes dark in latero-posterior region. Antenna strongly verticillate, 1.95–2.15 mm (2.03 mm); flagellomeres dark scaled. Proboscis 2.50–3.00 mm (2.71 mm); golden scaled dorsally, pale scaled ventrally. Maxillary palpus pale scaled ventrally, length 2.35–2.90 mm (2.60 mm). Thorax: Scutum integument darker than female. Postpronotum with 3–6 (3) setae. Mediotergite darker. Pleural setae as follows: 3–5 proepisternal, 5–8 (6) prealar, 3–6 and 2–4 (3) upper and lower mesokatepisternal, respectively, 3–7 (5) and 1,2 (1) upper and lower mesanepimeral, respectively. Scutellum darker; 6–7 (7) and 4–5 (5) median and lateral large scutellar setae, respectively. Wing: Length 3.09–3.76 mm (3.57 mm). Legs: Fe-1 2.30–2.60 mm (2.36 mm); Fe-2 2.10–2.75 mm (2.40 mm); Fe-3 2.15–2.75 mm (2.43 mm); Ti-I 1.45–3.00 mm (2.55 mm); Ta-1-I 0.55– 2.15 mm 1.59 mm); Ta-2,5-I 1.00– 1.85mm (1.51 mm). Unguis with secondary teeth. Abdomen: Tergum II-VI with a complete basal band of pale scales in following proportions: II-Te 0.57, III-Te 0.50, IV-Te 0.47, V-Te 0.51, VI-Te 0.59. Genitalia ( Fig. 2 , 3, 4): Gonocoxite short, length approximately 1.5 the widest part, with 16–20 strong setae along the external border of the gonocoxite. Subapical lobe with two structures, a large leaflet with serration on upper margin and ending in a long filament, and a tubular process ending as open arms. Median lobe of gonocoxite with 3 setae as rods, a short blunt rod, a strong hooked rod somewhat longer, and a modified rod, the longest and with the apex shaped as a flag with a furcate tip. Adjacent to these setae and to the middle of gonocoxite a semicircular lobe with 9–28 strong setae as rods with twisted apices and 2,3 normal setae, and a small dome with a patch of 16–20 setae. Gonostyle different, curved, of normal appearance in lateral view, in ventral view wide with an oval depression toward the apex where among 5–8 setae can be found, and ending in two divergent branches. The apex appears rough, has the normal claw of Culex , and distally forms a conical protuberance (spiny crest according to Stone, 1956) ( Fig. 3). Phallosome: Dorsal arm short, rough, reaching the first teeth of lateral arm. Ventral arm less differentiated of the 3–5 teeth of lateral arm, all striated. Lateral plate curved, partly surrounding the teeth, with the external edge toward the tergum. Dorsal process almost triangular. Proctiger: With a tuft of short pointed spines, basal arm very short with round apex, with 15–19 cercal setae. IX th tergal lobe small, with 5–9 setae in 1–3 rows.

Observations. Adult specimens of different Argentine provinces show great differences in size and other features such as presence and position of white scales on wing veins, as well as, the extent of the apical patch. The males from Mendoza Province are the biggest followed by males from Río Negro Province, reaching the mean length of Fe-I 3.00 mm and 2.33 mm, respectively. Adults from Buenos Aires Province showed white scales on 0.96 of the length of the R 2 vein (vein length = 1.55 mm), and 0.95 of the M 3+4 vein (vein length = 1.15 mm), while the proportion for adults from Mendoza Province were 0.56 of the R 2 vein and 0.8 of the M 3+4 vein (vein length = 1.35 mm and 1.00 mm, respectively). Males and females from Río Negro Province presented small patches of whitish scales in all tarsal joints. Males from Santa Fe Province showed a whitish ring at middle of proboscis .

PUPA ( Fig. 5a, b ). Placement and character of setae as figured; range and modal number of branches in Table 1. Cephalothorax: Integument yellow to tan, postscutal area, scutum (including medial keel) and distal extreme of legs darker. Metanotum tanned, dark brown in medial region, 11-Mtn the strongest of the segment. Trumpet conical, tan to brown, homogeneously or darker in traqueolar region and/or reticular area bordering the pinna; length 0.53–0.74 mm (0.61 mm), width 0.13–0.17 mm (0.15 mm), index 3.60–5.43 (4.019). Abdomen: Length 2.68–3.51 mm (3.08 mm); integument tanned, mid area of tergum I brown. Terga III–V with a dark brown spot in midline which could extends as a basal band until seta 4-III-V. Seta 1-I among 10–26 (15) branches; 0-II-VIII present in all terga, simple; 8-II absent in general if present, simple; 14-III-VIII simple, almost 15 µ. In some specimens seta 13-IV and its alveolus was observed on segments III,V,VI. Genital lobe: Slightly tan, homogeneous, the shape varying from round to square, mid-apical region with tiny spicules, midlateral margin irregular, length 0.23–0.27 mm (0.25 mm) in females. In males, tanned coloration, like a rectangle, with 4 lobes, 2 latero-external on the distal third, and others 2 lobes at apex of the genital lobe, length 0.51–0.55 mm. Paddle: Length 0.85–1.14 mm (0.94 mm), width 0.65–1.00 mm (0.83 mm), index 1.01–1.29 (1.14). Yellowish, outer margin visible until half; midrib evident lengthwise of paddle. Without spicules on margin, tiny spicules on surface; setae 1-P sometimes double or triple, 2-P always simple.

Observations. According to Harbach & Peyton (1992), the seta 6-I,II can be used as a differential character to separate the subgenera Phenacomyia (hardly if at all longer than 7-I,II) and Culex (usually distinctly longer than 7-I,II), but in Cx. (Cux.) apicinus described here the seta 6-I,II was as long as 7-I,II. The presence of supernumerary setae was observed in some specimens as follows: two setae 9-V on left side (RN 6-21), two setae 11-IV (RN 6-12), and seta 9b-CT bilateral (RN 7-11); seta 13-IV was present in several specimens: RN 6-109, BA 50-103, MZ 3-10, 15 bilateral, RN 6-13, BA 50-12, BA 50-109 on the left side, in RN 7–12 in the right side, the alveolus of this seta was usually present in the segments III,VI.

LARVA (fourth instar) ( Figs. 5 , 6 ): Setae as figured, range and mode of setal branches given in Table 2. Head: Wider than long, hardly tanned, lateralia and dorsal apotome tanned. Dorsomentum with 6,7 (6) teeth on both sides of median tooth. Maxilla ( Fig. 5c, d ) Culex type. Setae 0-2-C present, 1-C not tanned with barbs, 4-C usually single 5,7-C aciculate strongly developed, 8-C usually with 2 branches, 9-C usually with 4 branches, 10-C with 1–3 branches, 11,12-C usually with 2-6 branches, 13-C with 2–5 branches, 14-C usually single, 15-C usually double with 1-4 branches, 16,17-C absent, 6-Mx single, longer than 4-C ( Fig. 5 ). Collar dark. Antenna: Length 0.54–0.66 mm (0.60 mm), slightly tanned with dark ring at base, proximal part aciculate, less aciculate laterally on distal part. Seta 1-A with 15–30 (24) aciculate branches, inserted about 2/3 from base. Thorax: Integument hyaline, smooth, tubercles of all large setae tanned. Seta 0-P with 6–12 branches, seta 1-P usually 1,2 (2), seta 2-P single, mainly same length that 1-P, seta 3-P usually 2,3 (2), 4-P usually triple (1–4), 5-P usually double, 6-P single, 7,8-P normally triple, 11-P with 1–4 branches, others single. Seta 1-M with 1–4 branches, 3-M single, similar in length to 1-M. Setae 1-T with 2-6 branches, usually quadruple, 3-T long, usually with 3 branches (2–7). Abdomen: Cuticle smooth, except on segment VIII around comb area. Tubercles of setae 6-I,VI, 7-I, 1,3-VIII tanned. Seta 1-I with 3–9 branches, 1-II with 1–6 branches, 1-III,V usually with 4 branches. Segment VIII: Comb with 24–32 scales arranged in 3 or 4 irregular rows, normally fringed. Segment X: Saddle complete, length 0.39–0.45 mm (0.41 mm), tanned, with distinct spicules on posterolateral margin. Seta 1-X usually double (2–4), 2-X with 1–5 branches, 4-X with 11–15 (12) setae. Siphon: Length 1.23–1.59 mm (1.36 mm), width 0.37–0.52 mm (0.45 mm), and in specimens with the major width near the middle 0.40–0.59 mm (0.49 mm), siphon index 2.53–3.30 (2.97), tanned, pecten on basal 0.65, with 5–11 spines with 1–4 basal denticles on one side. Seta 1-S usually in 5 pairs, 1a, 1b-S inserted into the pecten spines, 1e/f-S out of line, 1a,d/e-S usually with 9 branches, if 1e/f-S present usually with 6 branches.

Observations. A double seta 5-C was observed on left side of one specimen (larva MZ 3-12 ) , which also had seta 0-C in the dorsal position. An alveolus between setae 6-Mx and 14-C was observed in some specimens. An extra single seta was observed basaly to 1a-S in one case. Seta 1f-S occasionally present. Seta 6-S double in one specimen.

EGG: in raft formed among 30 and more than 70 eggs, of Culex type, with corion smooth, 0.67–0.77 mm length.

Material examined. Culex (Culex) apicinus : 50M, 27 MG, 53F, 86 Pe, 2P, 42 Le, 44L as follows: Argentina, Buenos Aires ( BA), La Plata, City Bell (34° 52’08’’S – 58° 02’ 32’’W) ( BA 50 ) , 2M, 1 MG, 6F, 9 Pe, 3L, 28-X-2004, Rossi coll., domiciliary irrigation channel; La Plata city (34° 55’ 45’’S – 57° 57’ 36’’W) ( BA 56 ) , 8M, 2 MG, 7F, 15 Pe, 1P, 7 Le, 2L, 12-XII-2005, Rossi coll., water tank; idem, 1M, 1 MG, 16-V-1999, L. Elizalde coll.; Bolivar (36° 14’ 01’’S – 61° 07’ 00’’W) , 13L, 15-I-1998, tires; Benito Juarez (37° 40’ 57’’S – 59° 39’ 57’’W) , 1M, 1 MG, 18-XI-1998; Mor ó n (34° 38’ 59’’S – 58° 36’ 59’’W) , 2L, 28-X-1998, artificial container; Azul (36° 46’ 57’’S – 59° 50’ 56’’W) , 1M, 2F, 16-V-1998, Dpto. Zoonosis Rurales PBA coll., tires; Santa Fe: Venado Tuerto (33° 45’ 59’’S – 61° 57’ 57’’W) , 3M, 1 MG, 19-XI-1988, Camino coll.; Córdoba: Río Tercero (32° 11’ 01’’S – 64° 07’ 00’’W) , 1M, 1 MG, 1 Pe, 1L, 19-XI-1988, Camino coll., ditch; Villa María (32° 24’ 49’’S – 63° 13’ 57’’W) , 4M, 3 MG, 1L, 19-XI-1988, Camino coll., ditch; Mina Clavero (31° 42’ 59’’S – 65° 01’ 00’’W) , 1P, 5L, 22-XI-2007, Rossi coll., pool near the river; Pampa de Achala (31° 36’ 15’’S – 64° 49’ 24’’W) , La Pampilla, 2L, 24-XI-2007, Rossi coll., flooded plain; Villa Allende (31° 18’ 00’’S – 64° 16’ 59’’W) , 2F, 2 Pe, 2 Le, IV-2007 Ludue ñ a coll., swimming pool; C ó rdoba (31° 24’ 18’’S – 64° 10’ 47’’W) , 2F, 2 Pe, 2 Le, 16-VIII-1984, Almir ó n & Buffa coll.; Yuspe (31° 22’ 38’’S – 64° 46’ 14’’W) , 3M, 3 MG, 2F, 3 Pe, 3 Le, 13- II- 1995, Almir ó n coll.; San Luis ( SL): Villa de Merlo , 855 masl (32°20’58’’S – 65°1’15’’W) ; 3M, 3 MG, 2F, 5 Pe, 5 Le, 20- III- 2007, Musicant coll., swimming pool. La Rioja ( LR): Patquía (30° 03’ 01’’S – 66° 52’ 58’’W) , Guayapas, 2M, 2 MG, 5F, VIII-1960, Carcavallo & Yivoff coll., water with chlorine sulphate (20%); National Park Talampaya (29° 54’ 07’’S – 67° 31’ 21’’W) , 1 MG, 2F, 3 Pe, 2 Le, 17-X-2004, Laurito coll., natural pond; Cuesta de Miranda , 3M, 1 MG, 5F, 9 Pe, 3 Le, 1L, 18-XI-2007, Miranda river , 1620 masl (29°20’50.4’’S – 67°42’12.7’’W) , 18-XI-2007; R í o Vinchina and Route (76 28°42’19.4’’S – 68°18’22.9’’W) , 1F, 2 Pe, 04-XI-2007, Rossi coll., 1660 masl.; Salta ( SA): Quebrada de Escoipe (25° 10’ 51’’S – 65° 43’ 00’’W) , 1F, 1Pe, 1Le, 19-X-2000, Molina coll.; Chorro Blanco river. Mendoza ( MZ): Uspallata (32° 35’ 46’’S – 69° 20’ 35’’W) (Mz 3) , 1M, 1 MG, 1 Pe, 01- III- 1989, Garc í a & Marino coll.; Potrerillos (32° 57’ 00’’S – 69° 12’ 00’’W) , 3M, 1 MG, 2F, 6 Pe, 6 Le, 22- II- 2002, Scheibler coll., overflowing of Uspallata river, 650 masl; Río Negro ( RN): Epulauquen Lake , 3L, 23- II- 2001, Spinelli coll.; Meseta de Somuncur á (41° 33’ 39’’S – 66° 19’ 04’’W) , El Rinc ó n farm, 1M, 1 MG, XI-1999, Muz ó n coll.; Idem La Rinconada farm ( RN 6 ), 6M, 2 MG, 3F, 9 Pe, 3 Le, 9L, 07-XII-2006, spring stream; idem ( RN 7 ) 7M, 2 MG, 11F, 18 Pe, 8 Le, 5L, between rocks on spring, both Rossi coll.

Distribution. Culex apicinus is known from Chile, Bolivia, Perú and Argentina ( Martinez et al., 1960, Knight & Stone, 1977). In Argentina it is recorded from the provinces of Buenos Aires, Catamarca, C ó rdoba, Corrientes, Jujuy, La Rioja, Santa Fe ( Rossi, 1995; Campos & Maci á, 1998), Río Negro (Muz ó n et al., 2005), San Luis ( Visintin et al., 2008 in press), Salta is a new province record.

Bionomics. Culex apicinus do not bite humans, probably it is fed on dogs, cats or farm mammals. Immature stages were collected throughout the year except June and July from temporary to permanent, natural (pools near rivers originated by rainfalls or overflowing, stream edge, water bodies between rocks, hole in rocks) and artificial (domiciliary irrigation channels, water tanks, ditches, swimming pools) mosquito larval habitat, including water treated with chlorine sulphate.

Discussion. By its characteristics the adult of Cx. apicinus is sufficiently different like being easily distinguishable of other Culex (Culex) species as well as the larva of fourth stage, mainly by the conformation of the siphon and the tanned dark of he himself, the head and anal segment (X). The pupae on the contrary is very similar to others of the subgenus, except by the trumpet shape, the presence of at least the alveolus of seta 13- III–VI and the paddle with tiny spiculosity on the surface.

Figures

FIGURE 1. Female genitalia structures of Culex (Culex) apicinus Philippi. Ce = cercus; PGL = postgenital lobe; I = insula.

FIGURE 2. Male genitalia structures of Culex (Culex) apicinus Philippi: a: Gonocoxopodite; b: Phallosome and Paraproct (dorsal); c: tergum IX (dorsal). BL = basal arm; DA = dorsal arm; DP = dorsal process; GC = gonostylar claw; Gc = gonocoxopodite; Gs = gonostylus; LA = lateral arm; PpC = paraproct crown; Ppr = paraproct; Pr = proctiger; SL = subapical lobe; ML = median lode; VA = ventral arm; IX-Te = tergum IX.

FIGURE 5. Pupa of Culex (Culex) apicinus Philippi. a: Cephalothorax; b: Abdomen. Maxillae of larva of Culex (Culex) apicinus Philippi. c: ventral aspect; d: dorsal aspect. A = antenna; CT= cephalothorax; Dap = dorsal apotome; GL = genital lobe; MK = median keel; Mtn= metanotum; Pa = paddle; T = trumpet. MxB = maxillary brush.

FIGURE 6. Larva of Culex (Culex) apicinus Philippi. A = antenna; C = cranium; CS = comb scales; Dm = dorsomentum; PS = pecten spines; S = siphon; VII, VIII, X= abdominal segments.