90 



Range. — Massachusetts, Ohio, District of Columbia, Maryland^ 

 Mississippi. 



Described from the following material: one male and one 

 female reared from the nest of Bicyrtes quadrifasdata Say, 

 taken at Adaton, Mississippi, August, 1922. and three females 

 collected about a Bembicid colony at the same locality (H. W. 

 Allen) ; one male. Agricultural and Mechanical College, Missis- 

 sippi, August 7, 1922 (H. W. Allen). In the U. S. National 

 Museum, aside from the type and allotype: one female taken as 

 it emerged from the nest of Bemhex spinolae, June 6, 1914, Wash- 

 ington, D. C. (J. B. Parker) ; one female labeled 'Tarker Note No. 

 44," concerning which Professor Parker has furnished the informa- 

 tion that, ''this fly was captured as it emerged from the nest of 

 Bicyrtes ventralis Say, into which it had dashed in pursuit of the 

 wasp as she entered with a Hemipterous insect." A male from 

 Glen Echo, Maryland, August 30, 1923, in the collection of 

 J. R. Malloch. A male and a female taken in coitu, at West 

 Springfield, Massachusetts, July 25, 1915 (H. E. Smith), loaned 

 by the Museum of Comparative Zoology, agree with the type in 

 the number and position of the orbital bristles and in the degree 

 of thickening on the arista, but the front is narrower as in ruhri- 

 ventris, and there are no median marginal bristles on the second 

 abdominal segment in either; also two specimens from the same 

 locality in the collection of the Boston Society of Natural History. 

 A single female specimen reared from puparium taken from sand 

 beneath the burrows of Bemhex spinolae and other fossorial 

 Hymenoptera, at Columbus, Ohio, August 10, 1921 (H. W. Allen), 

 in my collection, agrees with the type in the width of the front, 

 in having the arista thickened no more than the basal half and in 

 the presence of conspicuous blackish tomentum on the third 

 antennal joint. It differs slightly, however, in having two pro- 

 clinate orbitals. 



This species is very closely related, morphologically, to litoralis. 

 However, in the specimens that I have examined, the presence of 

 a large amount of red on the abdomen is constant in vigilans, while 

 in litoralis there is never any reddish coloration. Some specimens 

 of vigilans vary toward ruhriventris. Males of these two species 

 may always be readily separated by comparison of the outer 

 forceps which are hooked toward the tips of the inner forceps in 

 the former, away from them in the latter. In both sexes of 

 vigilans, the bucca and front are wider, the arista is more ex- 

 tensively thickened than in ruhriventris, and there is one less 

 proclinate orbital bristle. 



Senotainia litoralis, new species. 

 Male. — Front at narrowest 0.32 of head-width, (measurements of five as 

 follows: 0.29, 0.31, 0.33, 0.33, 0.34); frontal vitta behind base of antennae 

 scarcely wider than lowest ocellus, broadening gradually to width greater than 

 parafrontal at the ocellar triangle; posterior two-thirds of vitta distinctly 

 pollinose, obscure; face and front silvery; a frontal row on either side of vitta 

 of about nine weak bristles, separated at their middle by distance less than 



