280 FREDERICK KNAB. 



Columbia : Boca de Arquia, Atrato River, v. 1914:, attacking man (Dr. A. Balfour). 



This species is closely related to S. amazonicum, Goeldi, and shows very similar 

 thoracic ornamentation. It differs in the absence of the iridescent green-blue bands, 

 present in that species at the apices of some of the abdominal segments. There are 

 also less appreciable differences in the coloration of the legs and in other details. 



Simulium limbatum, sp. nov. 



Female. — Head blackish, both frons and lace with strong metallic blue and pearly 

 lustre ; frons broad above and distinctly narrowing toward the antennae. Antennae 

 blunt, the first two joints yellow, the following ones luteous brown, slightly pruinose 

 and with delicate white pubescence. Scutum deep chocolate-brow^n, with pearly, 

 pale blue ornamentation consisting of broad lateral margins involving the humeri 

 and a narrower posterior margin, as well as two large wedge-shaped spots on the 

 anterior fourth, their blunt ends resting on the anterior margin and their sharp ends 

 continued as narrow lines beyond the middle of the disk ; vestiture of rather long 

 silvery hair- scales, rather sparse and not disposed in groups or regular series. 

 8cutellum broad, the hind margins slightly sinuate and converging nearly rectangularly 

 to the apex, dark ferruginous brown, nude on the disk, with coarse black marginal 

 bristles. Postnotum blackish, gray pruinose. Pleurae blackish and uniformly gray 

 pruinose. Abdomen subcylindrical, black, the second, third and fourth segments 

 dull, the others shining, without markings, the apical margins of the segments narrowly 

 pale. Legs slender ; coxae and trochanters of all three pairs ochreous, tinged with 

 brown on the hind pair. Front legs with the femora and tibiae ochreous yellow, the 

 former paler apically, the tibiae with silvery white pruinosity on outer side except 

 at base ; tarsi wholly brownish black. Middle legs with the femora brown, broadly 

 pale ochreous at apex, the tibiae brown in the middle, both base and apex broadly 

 pale ochreous, their outer sides on the basal half with a white pruinosity terminating 

 obliquely ; tarsi with the first joint long and slender, whitish, brown on distal fifth, 

 the second joint broadly white at base, the last three joints wholly brown. Hind 

 legs with the femora and tibiae dark brown, the latter broadly yellowish at base, 

 their outer sides with a white sheen on basal half ; tarsi with the first joint slender, 

 compressed, nearly as long as the tibia, white, its ventral margin and the distal fourth 

 blackish, second joint white on the basal half, the last three joints wholly black. 

 All the femora and tibiae with long, recumbent, shining yellowish white hair-scales. 

 Claws simple. Wings broad, the venation normal ; thick veins brownish yellow, 

 the costal spines short, stout, dense and black ; integument iridescent, more 

 pronounced and predominatingly red on basal half, but not forming a pronounced 

 spot. Halteres white, brownish at base. 



Length : Body about 1*3 mm. ; wing 1*7 mm. 



British Guiana : Rupununi River, ix. 1913 (Dr. K. S. Wise). 



A series preserved in spirits received together with a larger number of S. amazonicum, 

 Goeldi. 



This species belongs to the same group as S. amazonicum and shows its relationship 

 by the close agreement in structural and other details. It differs strikingly in the 

 absence of the pair of thoracic dorsal stripes. The two species were preserved 

 together in the same vials, so evidently occur together. 



