228 Journal Xew York Entomological Society. [Voi. xx. 



elongated lobe, beset with stout hairs; the guard of the penis is short 

 and stout; anal tube very short. In a position of rest, the appendages 

 tightly fit into grooves on the ventral side of the pleural pieces. 



Ovipositor of the female with the valves rather short, straight, 

 pointed. 



Key to the Species of Brachypremna O. S. 



1. Basal deflection of i?4+5 obliterated, so that R.+z and R^^-^ arise directly from 



the end of the radial sector; Rg elongate; cell ist M„ sub-triangular; legs 



uniform brown. (Antilles.) nnicolor O. S. 



Basal deflection of R^^^ prominent; Rg shorter; cell ist M„ sub-quadrate; 

 legs variegated with white or yellowish-white 2 



2. Femora with the tip dark, brownish-black 3 



Femora with the tip abruptly light-colored, white or yellowish-white 5 



3. Tibise uniformly pale, whitish. (East U. S.-Brazil.) dispellens Walker. 



Tibise more or less dark colored 4 



4. Tibiffi white at the extreme base only. (Guiana, Brazil, Bolivia.) 



breviventris Wied. 

 Tibiae white at the base and tip. (Guiana-Brazil.) zvilliamsoni^ n. sp. 



5. Tip of tibiae broadly pale ; tarsi pale 6 



Tip of tibise and the tarsi dark, concolorous with remainder of the legs. 



(Mexico-Panama.) similis Williston. 



6. Tibiae with a narrow dark band, three mm. broad, situated one and one half 



mm. from the base. (Brazil.) pictipes O. S. 



Tibiae with the dark median band, broad, comprising about half the length of 

 the segment. (Guiana-Brazil.) Candida n. n. 



Brachypremna dispellens Walker. 



i860. Tipitla dispellens Walker, Trans. Ent. Soc. Lond., Vol. 5, new series, p. 



334. 1878. Tipnla dispellens Osten Sacken, Cat. Dipt. N. Am., ed. 2, p. 39. 



1886. Brachypremna dispellens Osten Sacken, Berl. Ent. Zeitschr., Vol. 30, 



p. 162. 1900. Brachypremna dispellens Williston, Biol. Cent.-Amer., Dipt., 



Vol. I, suppl., p. 229. 1909, Brachypremna dispellens Johnson, Boston 



Soc. Nat. Hist. Proc, Vol. 34, p. 123. 



Head : rostrum light brown, the nasus rather short, dark brown ; palpi, 

 basal segment dark brown ; second, brown at the base, paler, yellowish-white, 

 apically ; third segment entirely pale ; fourth segment dark brown. Antennae, 

 basal segments pale, flagellar segments light brown, the apices of the segments 

 indistinctly paler. Front, vertex and occiput rather dark brown, except a very 

 narrow, pale border adjoining the inner margin of the eye; center of the vertex 

 clear-gray. 



Thorax : prothoracic scutum pale, the lateral margins dark brown and two 

 elongated spots on either side of the median line. Mesonotum, praescutum light 

 brown, the extreme cephalic margin and the lateral edge, paler, whitish ; a dis- 

 tinct narrow brown line, arcuated outwards at the cephalic margin of the sclerite, 



