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ABSTRACT. A new species of Downeshelea Wirth & Grogan, 1988, D. oliveirai (Lane & Wirth, 1964) and D. guianae (Wirth, 1953), are reported from northern Brazil.Material from light trap collections from Rondônia and Pará states included an undescribed species of Downeshelea that we describe herein.The terminology used is that adopted by WIRTH & WILLIAMS (1964) for North American species of Monohelea Kieffer, 1917, LANE & WIRTH (1964 for Neotropical species, and RATANAWORABHAN & WIRTH (1972) for Oriental species. The terms of wing veins follow the system of the Manual of Neartic Diptera (MAC ALPINE et al., 1981), with modifications proposed by SZADZIEWSKI (1996). All measurements are in micrometers, except those of the wings which are in millimeters. Head. Brown. Eyes (Fig. 4) bare, narrowly contiguous in lower portion. Antenna (Fig. 3) brown except on basal portion of flagellomeres; flagellomeres cylindrical, with mean lengths of 59-40-42-43-43-48-48-48-75-75-80-80-101 μm (n= 9), Antennal Ratio (11-15/3-10) 1.08-1.17 (1.11; n=9). Palpus (Fig. 5) uniformly brown, longer than proboscis; lengths of segments 29-48-74-42-58 μm; 3 rd segment cylindrical, slightly swollen distally, with a moderately deep sensory pit in mid portion; Palpal Ratio 2.2-2.8 (2.6; n=9). Mandible with 11 teeth. Downeshela oliveiraiThorax. Brown, without definite pattern in slide mounted specimens. Legs (Fig. 8) brown, the hind slightly darker; knees yellowish; fore and hind tibiae with apical spur, longer in fore leg; hind tibial comb with six bristles; lengths of trochanters, femora and tibiae of fore, mid and hind legs 117-533-522, 117-640-608, 128-746-683 μm (n=10). Tarsi (Fig. 7) pale, pilose; ventral palisade setae in one row on hind basitarsus; fore and hind basitarsi with one basal and one apical spine; mid basitarsus with 2 basal, 2 apical and 3-4 ventral spines; apical spines of tarsomeres 2-4 of fore, mid and hind legs as follows: 1-1-1, 2-2-1, 1-1-2, basal spines absent; lengths of fore, mid and hind tarsomeres 245-117-74-53-106, 309-128-74-53-96, 458-192-117-85-85 μm (n=10); fore, mid and hind tarsal ratios 2.3, 2.4, 2.2 (n=6); claws of fore and mid legs paired, equal sized, about 0.6 times as long as 5 th tarsomere; hind leg with a single claw, about 1.1 times as long as 5 th tarsomeres. Wing (Fig. 1) hyaline, scattered macrotrichia distally in cell r 3 and m 1 , microtrichia absent; 2 conspicuous dark spots, one locate on the r-m crossvein reaching the medial fork, the other in cell r 3 , extending from the end of 2 nd radial cell to vein M1; six inconspicuous grayish, diffuse areas in apical portions of cells r 3 , m 1 , m 2 (this one reaching to vein M2 and extending from cell m 1 ), cua 1 (this one reaching vein CuA 1 ) and veins M1 and CuA 2 ; 2 nd radial cell nearly twice as long as 1 st ; costal ratio 0.77-0.81 (0.79, n=9).Abdomen. Brown. Two subspherical spermathecae (Fig. 6) slightly unequal, measuring 69 by 53 μm and 57 by 45 μm; a vestigial 3 rd present, 16 μm long. Male. Wing length 1.13-1.32 (1.27, n=5) mm; breadth 0....

Morphological alterations in six different species of females Culicoides Latreille, 1809 and one of Monohelea Kieffer, 1917 from Brazil, Mexico, Panama and Peru are described. The correlation of the morphological changes with the taxonomy and behavior of the species is discussed.