Pseudosmittia trapezoidea, Mauad, Melina, Siri, Augusto & Donato, Mariano, 2013

Mauad, Melina, Siri, Augusto & Donato, Mariano, 2013, New species of Pseudosmittia Edwards, 1932 and new records of Allocladius Kieffer, 1913 (Diptera: Chironomidae, Orthocladiinae) from South America, Zootaxa 3694 (5), pp. 445-460 : 451-454

Pseudosmittia trapezoidea sp. n.

( Figs 9–12 )

Material examined. Holotype male, ARGENTINA, Buenos Aires, Aº s/n RP 30, 34º 54' 30.9'' S, 57º 56' 21.8'' W, 13.iii.2007, sweep net, M. Donato (MLP).

Etymology. The name refers to the trapezoid shape of the inferior volsella.

Diagnosis. Distinguished from all other species of the genus by R4+5 ending proximal to M3+4; anal point parallel-sided covered by microtrichia; gonostylus slightly curved; virga consisting of double median spine without lateral spinules or additional structures; superior volsella consisting of rounded and low basal swelling of inner margin of gonocoxite; median volsella absent.

Male (n = 1). Total length 2.03 mm. Wing length 0.92 mm. Total length/wing length 2.20. Wing length/length of profemur 2.56. Coloration (specimens preserved in alcohol) uniformly dark brown with legs light brown.

Head. Antennae with 13 flagellomeres, AR 1.27, ultimate flagellomere 330 long. Temporal setae divided in 1 outer vertical, inner verticals lacking, and 2 postorbitals. Clypeus with 8 setae. Tentorium 115 long and 22 wide. Stipes 78 long and 7 wide. Palpomere lengths (1–5): 20; 32; 61; 78; 115.

Thorax ( Fig. 9 ). Antepronotum without lateral setae. Dorsocentrals 11; prealars 3; supraalar absent. Scutellum with 2 setae.

Wing ( Fig. 10 ). VR 1.6. C extension 28 long. Brachiolum with 1 setae; other veins bare.

Legs. Spur of front tibia 39 long; spurs of mid tibia broken; of hind tibia 15 long, the external tibial spur broken. Width at apex of front tibia 24; of midd tibia 24; of hind tibia 34. Comb with 11 setae. Lengths and proportions of legs in Table 3 .

Hypopygium ( Figs 11–12 ). Tergum IX with 14 setae, laterosternite IX with 3 setae. Anal point 35 long, parallel-sided. Phallapodeme 20 long; transverse sternapodeme 86 long. Virga 39 long. Gonocoxite 134 long; length from base of gonocoxite to apex of inferior volsella/length of gonocoxite 0.45. Gonostylus 76 long; megaseta 12 long. HR 1.76; HV 2.66.

Remarks. Peudosmittia trapezoidea keys to couplet 10 of Andersen et al. 2010, the absence of a postcubital fork in this species fits in the first option but differs with the other character proposed since the anal point is very strong with parallel sides. In Ferrington & Saether (2011) P. trapezoidea keys with P. parifusata Ferrington & Saether but differs from this species in having LR1 0.45, superior volsella absent and the shape of inferior volsella without accessory lobe.

Habitat. The species Pseudosittia trapezoidea was collected in the shores of one of the first order tributaries of the El Pescado stream. This last stream is a tributary of the Rio de La Plata. It is characterized by a low flow rate with limited transport capacity. This parameter, however, becomes modified as a result of higher precipitation usually occurring about twice a year during autumn and the late spring. El Pescado stream is characterized by neutral to slightly alkaline water with low conductivity, high turbidity and moderated dissolved-oxygen and nutrient concentrations.

Figures

FIGURES 9 – 12. Pseudosmittia trapezoidea sp. n., male. 9, Thorax; 10, Wing; 11, Hypopygium with tergite IX removed, dorsal aspect to the right, ventral aspect to the left; 12, Hypopygium, dorsal aspect.

Tables

TABLE 3. Lengths (in µm) and proportions of legs of Pseudosmittia trapezoidea sp. n. (male, n = 1). For abbreviation explanations see Table 1.

fe	ti	ta1	ta2	ta3
P1 360	400	180	80	60
P2 420	440	190	100	70
P3 420	460	240	120	110
ta4	ta5	LR	BV	SV
P1 50	50	0.43	3.67	4.21
P2 50	50	0.52	3.39	3.67
P3 60	40	-	-	-