Isostomyia paranensis (Brèthes), Brethes

Campos, Raúl E. & Zavortink, Thomas J., 2010, Description of the larva and pupa and redescription of the adults of Isostomyia paranensis (Brèthes) (Diptera: Culicidae), Zootaxa 2689, pp. 27-36 : 28-34

Isostomyia paranensis (Brèthes)

1910. Lynchiaria paranensis Brèthes 1910: 471. TYPE: Lectotype female, Tuyupare [small watercourse in Delta del Parana], Buenos Aires, Argentina, 25 Jan 1908, J. Brèthes [Museo Argentino de Ciencias Naturales; designation by Casal in Belkin et al. 1968: 11].

Lynchiaria paranensis: Brèthes 1912: 40 ; Pennington 1919: 600.

Lesticocampa paranensis: Dyar 1919a: 10 ; 1919b: 85.

Goeldia paranensis: Bonne-Wepster and Bonne 1921: 18 ; Dyar 1921: 149; Bonne-Wepster and Bonne 1922: 38; Dyar 1922: 99; Dyar 1923: 81; Petrocchi 1923: 91.

Isostomyia paranensis: Dyar and Shannon 1924: 482 ; Shannon and Del Ponte 1928: 97; Dyar 1928: 93 (in part); Shannon 1931: 499; Costa Lima 1931: 68; Campos and Maciá 1998: 301, 302; Marti et al. 2007: 252 –258.

Goeldia (Goeldia) paranensis: Edwards 1930: 301 ; Edwards 1932: 72; Lane 1939: 164.

Trichoprosopon (Hyloconops) lunatus: Lane and Cerqueira 1942: 515 (in part); Duret 1949: 124; Martínez 1949: 43; Duret 1950: 313; Duret 1951: 373.

Trichoprosopon (Rhunchomyia) lunatus: Lane 1953: 842 (in part); Prosen et al. 1960: 112.

Trichoprosopon (Runchomyia) lunatum: Stone et al. 1959: 77 (in part).

Trichoprosopon (Runchomyia) lunatus: Castro et al. 1960: 560 .

Trichoprosopon (Runchomyia) paranensis: García and Casal 1965: 14 –16; Stone 1967: 202; Belkin et al. 1968: 11; Knight and Stone 1977: 314.

Runchomyia (Isostomyia) paranensis: Zavortink 1979: 59 ; Ward 1984: 249.

Runchomyia (Runchomyia) paranensis: Darsie 1985: 160 , 188, 210; Mitchell and Darsie 1985: 326; Ronderos et al. 1992: 4, 6, 7, 8; Maciá 1997: 143, 144.

? Goeldia lunata: Shannon 1931: 499 .

Female (fig. 1). Medium-sized, scarcely ornamented mosquitoes with mainly yellowish to amber integument. Head: Covered with broad flat scales; scales large dorsally, brown with very slight blue, blue-green or purple iridescence, sometimes appearing lustrous cream-colored to pale golden at some angles of observation; scales on sides and underside lustrous cream-colored to pale golden. Occiput with row of long dark brown erect scales posteriorly. Ocular setae numerous; interocular setae long, curved. Eyes contiguous above antennae. Clypeus bare, yellowish-golden to brown. Proboscis 2.5±0.29 mm long (n = 6), 1.3–1.4 length of femur I, slender, with dark brown scales above, paler scales beneath. Palpus short, 0.12–0.15 length of proboscis, apparently with 2 palpomeres, brown scaled. Pedicel of antenna without scales; flagellomeres with 6–8 setae in basal whorl. Thorax: Mesonotal integument amber to light brown anteriorly, becoming yellowish-golden posteriorly, scutellum yellowish to straw-colored. Anterior promontory with a few median and lateral setae; antealar area with a few setae; supraalar area with numerous setae; a few widely-spaced dorsocentral setae sometimes developed. Scutum with broad flat dull brown scales, mainly moderate in size, enlarged on supraalar and prescutellar areas. Scutellum with 4,5 long and a few shorter setae on each lobe; all lobes with large broad flat dull brown scales. Postnotum yellowish-golden, with 3,4 pairs of dark setae, without scales. Paratergite bare. Antepronota conspicuous, not approximated above, with row of numerous long dark setae; scales broad, flat, dull brown above, silvery-white to lustrous cream-colored below. Postpronotum without setae; covered with broad flat scales, brown above, silvery-white to lustrous cream-colored below. Pleural integument slightly shining, yellowish-golden to amber, without extensive bare areas. Prespiracular area with 2,3 setae; upper proepisternum with 3–5 setae; prealar knob with 4–6 weak and strong setae; lower katepisternum with 2,3 setae far below level of lower edge of mesepimeron; upper mesepimeron with 4–6 setae. Most pleural scale-patches dense and well defined; scales broad, flat, imbricated, silvery-white to lustrous cream-colored; hypostigmal, subspiracular and postspiracular areas with scales; katepisternum with scales dense above, sparse below; mesepimeron largely covered with scales; upper proepisternal scales few or none; upper part of anteprocoxal membrane with a few scales. Mesomeron small, its upper edge above base of coxa III, bare. Legs: Coxae with silvery-white to lustrous cream-colored scales. Coxal setae strong, long; coxa-I with 7–12 setae. Femora and tibiae dark brown scaled with cream-colored to yellowish scales on ventral and/or posterior surfaces. Tarsi dark brown scaled with light brown to creamy-brown scales on ventral and/or posterior surfaces. Claws simple as in figure 1. Wing: (3±0.31 mm long; n = 6). Dark scaled. Veins Rs and M with narrow spreading scales basally, broader scales distally. Vein 1A ending far distad of branching of Cu. Upper calypter with long row of setae. Alula with narrow marginal scales distad. Halter: Knob dark scaled, lateral surface and underside sometimes creamy-brown. Abdomen: Tergite I laterally and laterotergite with silvery-white scales. Tergites II–VII brown scaled with cream-colored scales laterally on II or II, III and in triangular apicolateral patches on III–VII or IV–VII. Sternites with scales entirely cream-colored.

Male (fig. 1). Essentially as in female except for sexual characters. Head: Palpus 0.8±0.04 (n = 16) length of proboscis; slender; dark scaled; palpomeres IV, V darker with relatively few setae. Antenna 0.6±0.04 (n = 16) length of proboscis; pedicel very large; flagellum densely plumose. Legs: Anterior claw I enlarged, with submedian secondary tooth; claws II, III small, simple.

Male genitalia (fig. 2). Segment IX: Tergite with pair of lobes, each lobe about as long as wide and with 5–7 moderately strong, short, weakly curved setae. Sternite large. Gonocoxite: Stout; setae and scales numerous, but without patches of specialized setae. Basal Mesal Lobe: Well developed; an elongate, oblique, sclerotized plaque bearing about 20–25 strong, attenuate, non-hooked setae distad; setae curved mesad, not extending to apex of gonocoxite. Gonostylus: Simple; strongly developed, moderately long, stout basally, strongly curved; with a few fine setae apically. Spiniform straight, slender, short, pigmented. Phallosome: Aedeagus weakly pigmented; distal lateral margin convex in dorsal aspect; with narrow pointed apical beak; without preapical teeth, serrations or spicules. Proctiger: Paraproct with 3,4 moderately large, dorsally curved apical teeth. Cercal setae 6–10.

Pupa (fig. 3). Cephalothorax: Very weakly pigmented. Seta 1-C strong, long, usually double, sigmoidally curved. Seta 5-C strong, as long as or longer than trumpet, 12–18b. Trumpet: Ver y w e ak ly pigmented. Moderately long, narrow, gradually widening from base to apex, pinna short. Abdomen: Ve ry weakly pigmented. Tergite VIII very strongly produced caudolaterally, extending to or beyond apex of median caudal lobe. Dorsal sensillum present on tergites III–V. Seta 3-I-III relatively well developed, as strong as seta 6 on segment I, longer than seta 7 on segment II, longer than seta 6 on segment III. Seta 5-IV strong, long, single; seta 5 on other segments much weaker and shorter; seta 5-V larger than seta 6-V. Seta 6-II strong, long, single; 6-VII weak, single or double, cephalad and usually slightly laterad of 9-VII. Seta 9-VII,VIII strong, long; 9- VII 24–29 b, nearly as large as 9-VIII; 9- VIII 20–25 b. Terminal Segments: Male genital lobe large, extending to or beyond apex of paddle. Paddle: Very weakly pigmented. Small, shorter than minimum length of tergite VIII, apex produced; midrib represented by spiculose strip; surface irregular but not spiculose; distal inner margin and apex with small spicules.

Larva (fig. 4). Head: 1.18±0.11 mm. Siphon: 0.53±0.04 mm. Anal Saddle: 0.71±0.04 mm (n = 12). Head: Weakly pigmented, with moderately long transverse slit-like occipital foramen, usually dark at both extremes. Hypostomal sutures straight or nearly so, subparallel, extending to posterior tentorial pits. Anterior margin of labiogula strongly produced laterally, inner edge of projection with long spicules. Dorsomentum with 7 (6–8) teeth on each side of median tooth. Maxilla modified for grasping, elongate, with short nonarticulated apical process and long, simple articulated maxillary claw. Seta 1-C strong. Setae 4-7-C single. Seta 5-C caudolaterad of 6-C, cephalad of level of 7-C. Seta 9-C closer to 8-C than to posterior margin of head. Seta 14-C weak, single. Antenna: Without spicules. Thorax: Seta 4-P specialized, its branches strong and strongly and densely aciculate basally, weak and weakly aciculate or smooth apically, not flame-shaped, and as long as or longer than 0-P. Seta 11-M,T strong. Abdomen: Seta 6-I, II usually 10b (9–11); seta 6-III usually double (double, triple). Seta 7-I, II 4-7 b. Seta 3-VII strong, long, single. Segment VIII: Comb scales 13–23, in single regular to irregular row, each scale usually evenly fringed. Siphon: Very weakly pigmented, with small spicules. Index 2.3–2.9. Pecten filamentous, midventral, filaments about 30, distal ones shorter and stronger. Seta 1-S strong, long, 4–6b, inserted at base of siphon. Seta 1a-S 2,3b, inserted 0.75 (0.70–0.79) distance from base of siphon. Seta 2-S stout, short, apex unequally bifid and curved. Accessory setae 2a-S usually 7,8 (7–11), multiple branched beyond base. Seta 6-S relatively strong, stiff, apex recurved. Anal Segment: Very weakly pigmented, with small spicules. Seta 1-X strong, long, single. Seta 2,3-X strong, long, usually 3,4b (3–5). Seta 4-X strong, long, 4,5b.

Systematics. Females of Isostomyia lunata and Is. paranensis can apparently be distinguished by the color of the scales on the upper part of the antepronotum. In Is. lunata , these scales are described as being dark with blue and violet iridescence ( Lane 1953, García & Casal 1965). In Is. paranensis , however, these scales are dull brown, without any iridescence.

The male genitalia of Is. lunata and Is. paranensis differ conspicuously in the development of the large setae of the basal mesal lobe. In Is. lunata , these setae are relatively few (6–9), long (extending to or beyond the apex of the gonocoxite), and remain coarse to near their apices, where they are flattened and sharply bent or hooked. In Is. paranensis , these setae are more numerous (about 20–25), shorter (not extending to apex of gonocoxite), attenuate, and are not sharply bent or hooked at the apex.

Pupae of Is. lunata and Is. paranensis appear to differ by: (1) the length of seta 5-C, which is shorter than the trumpet in Is. lunata , but as long as or longer than the trumpet in Is. paranensis ; (2) the size of seta 3 on the anterior abdominal segments, seta 3-I weaker than seta 6-I in Is. lunata but as strong as seta 6-I in Is. paranensis , seta 3-II smaller than seta 7-II in Is. lunata but larger than seta 7-II in Is. paranensis , and seta 3-III smaller than seta 6-III in Is. lunata but larger than seta 6-III in Is. paranensis ; and (3) the size of seta 5-V, which is subequal to or smaller than seta 6-V in Is. lunata , but larger than seta 6-V in Is. paranensis .

Larvae of the species appear to differ by: (1) the form of seta 1-P, which is shorter than seta 0-P and flameshaped in Is. lunata but longer than seta 0-P and not flame-shaped in Is. paranensis ; (2) the form of the comb scales in the dorsal part of the row, which have a distinct, large, spine-like apical projection in Is. lunata but are evenly fringed in Is. paranensis ; (3) the number of pecten elements, which are about 13–21 in Is. lunata but closer to 30 (27–30) in Is. paranensis ; (4) the branching of seta 1-X, which has 3 or 4 branches in Is. lunata but is single in Is. paranensis ; and possibly also by (5) the accessory dorsolateral setae of the siphon, which are 6 in number and branched near their bases in Is. lunata but 7–11 in number and branched beyond their bases in Is. paranensis .

Bionomics. Isostomyia paranensis is sylvan and associated with areas that flood. The immature stages of Is. paranensis studied here were found living in leaf axils of Androtrichum giganteum (Kunth) Pfeiffer, 1940 (Cyperaceae) ; they were associated with larvae of Wyeomyia (Menolepis) leocostigma Lutz, 1904 . Several immatures (Mean ± SD: 11.6 ± 8.47; n = 15) of Is. paranensis were observed coexisting in spite of the low water volume (35.6 ± 28.31 ml) retained by the plants. Third- and fourth-instar larvae of Is. paranensis are facultative predators. They usually grab mosquito prey by the mid-abdomen, ingest the internal tissue, and then reject the skin. Marti et al. (2007) reported that most Scirpus giganteus (= A. giganteum ) plants they examined harbored only 1 or 2 Is. paranensis larvae and that they did not find evidence of predation, the midguts of field-collected larvae containing mainly green algae.

Adults are present from October to May, with maximum abundance in March and April, and are most active at sundown ( Maciá 1995).

Distribution. Isostomyia paranensis is definitely known at present only from northeastern Argentina. Most published records are from Buenos Aires Province ( Brèthes 1910, 1912; Pennington 1919; Shannon and Del Ponte 1928; Edwards 1930; Costa Lima 1931; Prosen et al. 1960; García & Casal 1965; Belkin et al. 1968; Ronderos et al. 1992; Maciá 1997; Marti et al. 2007). It is recorded also from Corrientes and Misiones provinces by Duret (1951), Castro et al. (1960), and Campos & Maciá (1998). The record of Is. lunata from Iguazu, Misiones by Shannon (1931) may refer to Is. paranensis .

Material examined. Argentina, Buenos Aires Province, Ensenada, Boca Cerrada Adult males: 7, 7 /XI/ 1995; 4, 4 /III/1996; 1, 25 /VI/1996, Campos col.; 2, 4 /VII/1996; 1, 1 /VIII/1996, Maciá col. Adult females: 2, 7 /XI/1995; 5, 4 /III/1996, Campos col. Larva: 5, 7 /XI/1995; 8, 4 /III/1996; 3, 13 /III/1996. Pupa: 1, 7 /XI/1995; 1, 12 /XI/1995; 10, 4 /III/1996; 1, 13 /III/1996; 1, 25 /VI/1996, Campos col. ( MLP).