OF WASHINGTON. 141 



pointed at the end than in the 9 9 of other .species, and is 

 broadly tipped with black. The claws are shorter, hooked, 

 and the tips black. This is the case with the 9 $ of most 

 species ; the claws of the $ $ are usually linear and entirely 

 yellow. 



Acaulona costata v. d. Wulp, Biol. Centr.-Am., Dipt., II, 4. 

 This exceedingly interesting new genus and species of 

 Phasiidfs is founded on the description of two specimens, 

 which Mr. van der Wulp refers with a query to the $ sex. 

 The very short claws and pulvilli mentioned would indicate 

 the 9 The genus has much the facies of Trichopoda, as may 

 be seen from the excellent colored figure. 



Gymnosoma filiola H. L,w. I have taken this species here, 

 and have also specimens from Iowa, Nebraska, South Dakota 

 (Aldrich), and Minnesota (Lugger), while Loew described it 

 from Texas, and Mr. v. Roder has determined it in a collection 

 of flies from Porto Rico (1. c., 344). Loew mentions in his 

 description that he had not observed any 9 9 to have the 

 widely dilated abdominal spots so frequently seen in larger 

 species. I have, however, 9 9 in w r hich the black markings 

 extend over nearly the whole abdomen. 



G. fuliginosa Rob. Desv. This is our largest and most 

 robust species. It is abundant here, and I have taken it in 

 Michigan. The 9 , as in all Gymnosomas, has black on each 

 side of the front, the face with a silvery reflection, the thorax 

 wholly black shining, and the abdominal markings dilated. 

 The $ has only the lateral angles of the vertex black, the 

 face with a golden reflection, the forward part of the thorax 

 with yellowish or brassy pubescence, and the abdominal 

 markings confined to several small, round black spots. The 

 claws are nearly the same length in both sexes, but the wings 

 of the $ are as a rule slightly smaller than those of the 9 . 

 Desvoidy described the $ . It is perhaps a question whether 

 this is not the same as G. rotundata L. of Europe (see v. d. 

 Wulp, Tijd. v. Knt., 2d ser., II, 136). 



G. occidua Wlk. This is, without doubt, as Dr. Williston 

 has pointed out (Tr. Am. Knt. Soc., XIII, 296), the 9 of 

 Cistogaster divisa H. Lw. But Dr. Williston seems, in his 

 paper, to accept Loew's name, whereas Walker's, as it is ac 

 companied by a recognizable description, ought to stand on its 

 priority. 



G. par Wlk. This may best be placed as a synonym of 

 fuliginosa R. D., until some one decides from examination of 

 the type in Cambridge that it is not identical. There is little 

 doubt of its being the same. 



