"J:i8 BULLETIN 31, UNITED STATES NATIONAL MUSEUM 



yellow .spots, forniinji- a broadly interrupted fascia, behind these spots 

 bhick violaceous, the posterior inari^in metallic blue. Venter pallid 

 vellowish, first segment metallic blue, the last violaceous. Trochanters 

 with the immediate base of the femora yellowish. Femora irjreenish 

 bronze, the extreme tip of the fiotit and middle pairs yellowish ; hind 

 femora moderately thickened, with an obtuse i)rqjectiou below near the 

 tip on the lower side, and on the margin of ihe projection with black 

 spines. Front and middle tibiie very pallidly yellowish, nearly white; 

 hind tibi:e incurved, the hasal third whitish, middle third black-viola- 

 (•eous, distal third black; basal joints of tarsi liglit yellow, third joint 

 fuscous, the last two black. Teguhe white, the margin and the cilia 

 black. Halteres dilutely yellowish. Wings cinereous hyaline, near the 

 tij) a little more obscure, stigma and veins black. 



ADDITIONAL NORTH AJIERICAN SPECIES. 



Xylota arcuata Say, J. Acad. Phil., vi, 1G2; Compl. Wr., ii, 357.— Mexico. 

 Xylota subcostalis Walker, Trans. Ent. Soc. N. S., v, 291.— Mexico. 



SENOGASTER.* 



Senogasier Macquart, Hist. Nat. Dipt., i, 519, 1834; Dipt. Exot., ii,2,72. 

 Acrochordonodes Bigot, Bull.Soc.Eut.de Frauce, 1878, 131. 



$ . Slender, nearly bare, rather large species. Head hemispherical, 

 formed chiefly of the eyes. Antenna^ situated near the middle of the 

 head in profile, first two joints short, third rather large, oval ; arista 

 bare. Face small, short, subcarinate, concave from antennae to oral 

 maigin, epistoma truncate obliquely in front, margin of mouth horizon- 

 tal below ; cheek very narrow below the eyes. Eyes large, bare, with 

 an area of enlarged facets in front above the antennae; frontal triangle 

 small, eyes contiguous for a short distance, vertical triangle long, acute ; 

 posterior orbits narrow. Abdomen long, third segment very much con- 

 tracted, cylindrical, narrow, the abdomen again widened at the end. 

 Hind femora arcuate, thickened, with a strong bifid spine below, near 

 the tip. Wings small, shorter than the abdomen, marginal cell open, 

 third longitudinal vein bent gently into the first posterior cell, last sec- 

 tion of fourth vein gently sinuate, anterior cross- vein oblique, joining 

 the fourth vein beyond tlie middle of discal cell. ' 



It seems very probable that Acrochordonodes Bigot is but the female 

 of a true Scnogaster. The character in which this genus, founded upon 

 a female specimen, is said to difter, is precisely what might be expected 

 in that sex, viz, a less contracted abdomen. The type of Senogaster 

 is >S'. coerulescens Macquart (1. c), from Cayenne, South America. 



*2r£K65, slender; yadrr^p, abdomen. 



