354 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



I will name a new Tacliytrechus {Dolichoj).), related to T. moechus of the 

 Eastern States, which I used to find abundantly near the Trenton Falls, 

 New Tork; a new Spheconiyia (Syrphidce), a remarkable genus, of which 

 only two species were hitherto known, one in Europe and the other in 

 l^orth America, and those two may yet turn out to be identical 5 thirteen 

 species of the genus Gyrtopogon {Asilidce), eleven of ^hich were unde- 

 scribed, and some of them remarkably handsome (in Dr. Schiner's 

 Catalogue of Asilidce, published in 1866, only thirteen species of Cyrto- 

 pogon are enumerated for the whole world). The other orders of insects 

 afforded the same interest. Parnassiun was very common ; two new 

 species of Cicada were found, etc. 



Of the fauna of the Eocky Mountains, I had occasion to speak in 

 another place (Report on the Diptera collected by Lieutenant Carpen- 

 ter in Colorado in 1873, in the Annual Report of the United States Geo- 

 logical and Geographical Survey of the Territories for that year). The 

 relationship of the fauna in the higher regions of those mountains to that 

 of the northern latitudes of the continent is much more marked than 

 that of the fauna round Webber Lake in the Sierra. A series of char- 

 acteristic northern forms were found in Lieutenant Carpenter's col- 

 lection: — Resperinus hrevifrons (Bibionidce), which had been received 

 from Mackenzie River and collected by myself on Mount Washington ; 

 Arctoijhila Jlagrans, Tipula macrolabis, HelopMlus Mlineatus, etc. For 

 want of time, I did not collect much in the Rocky Mountains, but was 

 struck by the frequent occurrence, near Georgetown, Colo. (8.500 feet 

 altitude), of a species of Bejeania {TacMnidce), a genus which was hith- 

 erto received from South America and Mexico. Near Manitou, Colo, 

 (altitude 6,400 feet), another very large and peculiar Tachinid occurred, 

 of which I also have specimens, collected by Mr. Cleveland near San 

 Diego. 



Such facts, as well as many others mentioned in the course of the 

 present paper, prove that there is a great deal to be learned yet about 

 the laws regulating the geographical distribution of insects. In the 

 mean while, it is useful to keep such facts in view by singling them out 

 from the arid mass of descriptive entomology. 



