Simulium (Trichodagmia) itaunense D’Andretta & González B.

Hernández, Luis Miguel, Shelley, Anthony John, Dias, Antonio Paulino Luna & Maia-Herzog, Marilza, 2005, Redescription of the female, male, and pupa of Simulium itaunense D’Andretta & González B. (Diptera: Simuliidae), Zootaxa 896, pp. 1-14 : 3-8

Simulium (Trichodagmia) itaunense D’Andretta & González B.

(Figs. 1–23)

Simulium itaunensis D’Andretta & González B., 1964:106–108 . HOLOTYPE ♂ no. 856 (reared), BRAZIL: São Paulo State, Itatinga (Fazenda Itaúna); 17.vii.1957 (C. D’Andretta Jr.) (MZUSP).

FEMALE. General body colour black. Body length (specimen in alcohol) 4.2 mm (n = 1), (specimens pinned) 2.9–3.4 mm (mean = 2.9 mm, s.d. = 0.17, n = 3); wing length 2.8–3.1 mm (mean = 2.9 mm, s.d. = 0.17, n = 3), wing width 1.4–1.5 mm (mean = 1.5 mm, s.d. = 0.09, n = 3).

Head — dichoptic with dark red eyes and nudiocular area well developed (Fig. 1). Frons, clypeus and occiput black, with silvery grey pruinosity; clypeus and frons covered with recumbent white setae interspersed with dark, semi­erect black setae. Mouthparts dark brown to black. Antennae black with scape and pedicel dark brown. Cibarium unarmed or with undeveloped tubercles in the central trough, some of which have extremely fine denticles (only visible at high magnification); cornuae well developed and sclerotised (Fig. 2). [ Strieder (2004) stated that the cibarium in this species is armed with small tubercles (see Fig. 4, page 295), but these were not seen in one specimen in the material we studied.]

Thorax — scutum black, covered by recumbent, white setae. Scutal pattern varying only slightly with illumination. With anterior illumination, thorax black; humeri brownish with faint grey pruinosity; lateral and posterior margins black (Fig. 3). With posterior illumination, thorax black with grey pruinosity on anterior two thirds of scutum; lateral and posterior margins black (Fig. 4). Humeri brownish and weakly pruinose. Scutellum black with recumbent white setae interspersed with long, black bristles. Postnotum black with silver pruinosity. Pleura dark brown to black with silver pruinosity. Costa of wing with sparse distribution of spines and setae. Subcosta with only six setae in basal half (only setae insertions were visible in the single dissected specimen examined). Radius with line of setae intermixed with spines; basal section of Radius with hairs arranged in double Simulium itaunense female. Fig. 1: nudiocular area. Fig. 2: cibarium. Fig. 3: scutal pattern (light source anterior). Fig. 4: scutal pattern (light source posterior). Fig. 5: anterior wing veins. Fig. 6: fore, mid, and hind legs. Fig. 7: claw of mid leg. Fig. 8: abdomen. line on basal third (Fig. 5). Basal tuft of long, dark setae. Leg coloration and proportions as in Fig. 6. Foreleg with coxa, trochanter, and femur pale brown, tibia with basal and apical third and tarsal segments dark brown, pale yellow mesally. Mid and hind legs with coxae, apex of hind femur, apex of mid and hind tibiae and basitarsal segments I and II dark brown; trochanters, mid femur, basal half of hind femur, and basal half of mid and hind tibiae yellowish brown; basal two thirds of basitarsal segments I and II pale yellow. Claws curved without distinct basal tooth (Fig. 7). Halteres cream with brown base.

Abdomen — tergites I–IX shiny black, covered with recumbent white setae; tergite I silver pruinose on anterolateral margin (Fig. 8). Tergal plates developed; sternal plates undeveloped. Sternites greyish black; genitalia black. Eighth sternite sclerotised with irregularly distributed setae on posterior margin; gonapophyses crescent shaped, well developed, and touching centrally with apices curved in anterior direction, membranous and rounded distally, highly setose over entire surface (Fig. 9). Cerci subhemispherical, covered with brown setae; paraproct subtriangular, nearly same length as cercus, with small membranous process with hairs and setae and weakly sclerotised laterally; paraproct covered with prominent brown setae interspersed with small setae (Fig. 10). Genital fork stout and sclerotised; termination of lateral arms with anterior margin straight and developed; anterior and posterior processes well developed (Fig. 11). Spermatheca globular, without external sculpturing and with single spicules on internal surface; area of insertion of spermathecal duct weakly sclerotised, two fifths maximum width of spermatheca.

MALE. General body colour black. Body length (specimens pinned) 3.4–3.9 mm (mean = 3.7 mm, s.d. = 0.19, n = 4), wing length 2.7–2.9 mm (mean = 2.8 mm, s.d. = 0.06, n = 4), wing width 1.3–1.6 mm (mean = 1.4 mm, s.d. = 0.14, n = 4).

Head — holoptic with dark red eyes. Rest of head coloration as in female.

Thorax — scutum black with grey pruinosity, covered with golden, recumbent hairs. Scutal pattern, irrespective of light direction, consisting of 1 + 1 submedian, rounded silver pruinose vittae on anterior one third (Figs 12–13) [pattern more distinct with posterior light source]. Humeri weakly silver pruinose; lateral and posterior margins of scutum black [light source anterior or posterior], weakly silver pruinose when specimens viewed at an angle. Scutellum black with recumbent golden hairs interspersed with long, erect black hairs on posterior margin. Postnotum black with silvery grey pruinosity. Wing setation as in female, except Subcosta with fewer setae. Leg coloration as in female except legs darker brown.

Abdomen — tergites black, distinctly covered by golden, recumbent hairs; basal fringe with long, brown hairs (Fig. 14). Silver pruinose ornamentation on abdominal segments as follows: anterior margin of tergites IV and V [in dorsal view] and anterolateral margin of segments II and V–VII [best seen when specimen viewed laterally]. Genitalia black; tergal plates poorly developed and sternal plates well developed. Gonocoxite subquadrangular; gonostyle spindle­shaped, 3.5 times longer than length of gonocoxite at midpoint, with Simulium itaunense female and male. Female: Fig. 9: eighth sternite and gonapophyses. Fig. 10: cercus and paraproct. The arrow indicates the small membranous process. Fig. 11: genital fork. Male: Fig. 12: scutal pattern (light source anterior). Fig. 13: scutal pattern (light source posterior). Fig. 14: abdomen. Fig. 15: gonocoxite and gonostyle; inset, detail of apical spine. Fig. 16: ventral plate and median sclerite. Fig. 17: paramere. single, stout spine [sometimes with another smaller one]; gonocoxite and gonostyle covered with long setae (Fig. 15). Ventral plate sclerotised, with well­developed lateral shoulders, prominent, median, pear­shaped process arising from anterior margin covered with long hairs; basal arms straight, sclerotised and weakly narrow apically (Fig. 16). Median sclerite prominent, ovoid, nearly as long as width of ventral plate, with distinct incision to half of its length (Fig. 16). Paramere weakly sclerotised and poorly developed with no spines (Fig. 17).

PUPA. Cocoon length dorsally 3.7–4.3 mm (mean = 4.0 mm, s.d. = 0.21, n = 9), ventrally 4.5–4.9 mm (mean = 4.7 mm, s.d. = 0.14, n = 9); pupa length 4.1–5.5 mm (mean = 4.9 mm, s.d. = 0.39, n = 9); gill length 0.7–1.2 mm (mean = 0.9 mm, s.d. = 0.17, n = 11).

Cocoon shoe shaped as in Figs. 18–19, light to dark brown composed of thick coalesced fibres, with reinforced rim to anterior aperture; margin of aperture weakly elevated.

Gill light brown with 45–56 upwardly directed filaments arranged in bunch in vertical plane [specimens with 50 filaments are common]. Gill configuration with main trunk short, giving rise to four sets of primary branches, three external and one internal (Figs 20– 21). Primary branches bifurcate farther into secondary branches that are highly variable in number of filaments, all branching at different heights. In gills with the lowest number of filaments, the configuration is as follows: most dorsal of external branch often with 17 filaments, median 8 and ventral 7; internal set of filaments often consisting of 14 filaments. Variation of this pattern occurs on all primary branches. Filaments stout, pointed, and highly sclerotised distally, edges weakly crenate; all filaments approximately same length.

Head with 2 + 2 frontal and 1 + 1 simple, spiniform, facial trichomes; frontoclypeus with distinct group of platelets mesally, 1 + 1 dorso­laterally and 2–3 platelets in groups of 2 laterally in frontal region, respectively; tubercles rounded, densely distributed in facial region and absent from frontal region (Fig. 23).

Thorax with 4 + 4 distinct spiniform trichomes near margin of dorsal cleft (Fig. 22) and 2 + 2 simple trichomes on central region of thorax; tubercles mostly rounded on ventral margin near base of gill and pointed on posterior part of dorsal margin.

Abdominal tergite I with spine combs on posterior margin; tergite II with 3 + 3 submedian and 1 + 1 sublateral spiniform setae in longitudinal row and 1 + 1 long, simple setae anterior to most lateral of spiniform setae; tergites III and IV with 4 + 4 submedian, simple hooks in longitudinal row, sometimes 1 + 1 small, simple setae anterior to most lateral of hooks and 1 + 1 small, simple setae laterally; tergites V–VII with 1 + 1 small, simple setae laterally; tergite IX weakly sclerotised, without terminal spines. Groups of spine combs on anterior margin of tergites I–VIII. Abdominal sternite III with 1 + 1 submedian and 2 + 2 sublateral, small, simple setae; sternite IV with 2 + 2 submedian, spiniform setae; sternite V with 2 + 2 submedian, close bifid hooks; sternites VI–VII with 2 + 2 well­separated and bifid hooks. Abdominal sternites III–VIII with groups of spine combs on anterior margin.

Simulium itaunense pupa. Fig. 18: cocoon (lateral view). Fig: 19: cocoon (dorsal view). Fig. 20: right gill. Fig. 21: left gill. Fig. 22: spiniform thoracic trichomes. Fig. 23: frontoclypeus, inset showing frontal and facial trichomes, and tubercles.