378 C. R. OSTEN SACKEN'S PRODROME 



tlic dorsum, a grayif^li stripe, followed by a black one, between the root of the wings and the 

 humeri ; on the pleura3 a gray stripe, beset with long, yellowish hairs, is followed by a black 

 one, and then by a second gray stripe extending posteriorly over the base of the abdomen. 

 Abdomen black, with short, appressed grayish hairs. Legs black, first two joints of tl>e four 

 posterior tarsi livid, black at tip ; sometimes the middle and hind tibiae have a reddish tinge 

 at the root. Wings : second basal cell and fifth posterior cell hyaline, so that the crossbaud 

 is bounded posteriorly by the intercalary vein ; there is a hyaline spot just before the distal 

 end of the first basal cell (a vestige of the larger spot existing here in the other species of 

 the group) ; the crossband almost touches the posterior margin, the extent of the interven- 

 ing space not quite constant in different sj^ecimens ; apex hyaline. 



Hah. Middle and Northern States and British Possessions ; not rare. In some speci- 

 mens there is a paler streak in the fourth posterior cell, )jy the side of the intercalary vein ; 

 in others, a fixint brownish tinge appears in the fifth posterior cell ; or also on the margin at 

 the tip of the fifth and sixth veins ; sometimes there is a pale brown, very small cloud at 

 the base of the fork of the third longitudinal vein. 



I have a specimen from Illinois in wliich the first basal cell is almost entirely hyaline, 

 showing only a trace of a brownish tinge on its proximal half The specimen is a fully ma- 

 tured one, and otherwise normally colored. Until further evidence, I incline to think that it 

 represents only an accidental aberration. 



C. nlger in several respects forms the passage to the next group. Its ferruginous face and 

 the distinct longitudinal black stripes on the pleura foreshadow the coloring of that group. 



The mention of " face fauve " by Macquart, and the description of the wings, seems to 

 render the identification of this species certain, although the measurement given, five lines 

 (about 11 mm.), is too large for this species. 



Mr. Walker's description of C. nlger (List, etc., I, p. 202) is principally based on speci- 

 mens of C. sordidiis. His C carhonarms, var. ^ (evidently a different species from his 

 type) seems to belong to the present species. 



B. The apical portion of the wing, beyond the crossband, is more or less tinged with 

 brown, either in the shape of a distinct brown border along the costa, or of a separate api- 

 cal spot. 



8. Chrysops aestuans. 



Chrifsops cestuatis v. tier Wulp, Tijdschr. v. Eut., 2 Sor. II, p. 135 ; Tab. Ill, f. 8, 9. 



? C'hri/sops mocrens Walker, List, etc., I, p. 201. 



$ . Apical spot confined to a foint and narrow infuscation .along the costa ; both basal cells hyaline ; halo 

 along the crossband very distinct; the ends of the A-shaped black spot on the second abdominal segment ex- 

 pand into small black triangles on the posterior margin. 



Length, 10 mm. 



Female. Face, including the facial callosities, and cheeks yellowish-ferruginous, shining ; 

 facial orbits and the usual stripe between face and cheeks, powdered with yellowish-gray 

 pollen ; front covered with the same pollen, except the l)lack frontal callosity and a blackish 

 space on the vertex. Two basal joints of the antenna3 ferruginous, clothed with black hair ; 

 third joint blackish, ferruginous at base. Palpi variable in color, reddish or brownish, red- 



