North American Diptera. 5 



SniiNER. Fauna Austriaca, Diptera. 2 vols. Vienna, 1862-64. 



LoKM- and Ostkn Sackkn. Monofjraplis of North American Diptera. 

 4 vols. Smithsonian Institution, 1862-72. 



WiM,i!«TON. Synopsis of the North American Syrphidas. Bull. 

 V. S. National Museum, No. :;51, 1886. 



OsTEN SAf'KEX. Trodrome to a Monograph of the Tahanidaa. Bos- 

 ton Soc. Nat. Hist. 1875-8. 



LoEW. Diptera Centurise, 1860-1872. (One thousand new N. A. 

 species.) 



WiEDEMAXx. Aussereuropaeische Zzeifluegelige Insekten, 1828-30. 



MACQrART. Dipteres Exotiques Noveaux on pen Connus. 2 vols, 

 and 5 supplements, 1888-55. 



Meigen. Systematische Beschreihung der Europalschen Zweifiue- 

 geligen Insekten, 1818-38. (Useful for the figures.) 



OsTEN Saoken. Biologia Oontral-i-Americana, Diptera, 1886. (Ac- 

 cess to this work can only be obtained in large libraries.) 



ScHiXER. Novara Expedition, Diptera, 1868. 



Macqiart. Histoire nat. des Dipteres, Suites a Buffon. 2 vols. 1835. 



The above list has been arranged in about the order in which 

 the works will prove the most useful. 



In order to render the tables and descriptions intelligible to the 

 student wholly unacquainted with this order of insects, for whom, 

 indeed, the present work is more especially intended, some brief 

 descriptions of the peculiar terminology is necessary. The termi- 

 nology here used is essentially that of Loew, who gives a fuller exposi- 

 tion of it in the first volume of his monographs, works which, with 

 Osten Sacken's more recent catalogue, will be of first importance to 

 all those who would pursue the study further than that of mere 

 separation into families and genera. . 



Terjiinolooy of Diptera. — The large compound eyes are present 

 in all diptera, except some pupipara. In the majority of males they 

 are contiguous on the upper part (holoptic), rarely so in the 

 females. The narrow border, immediately surrounding them is 

 the ORBIT, indicating often a more or less indefinite space. When 

 the eyes are separated (dichoptic), as they are in most females and 

 many males, the space between them, limited above by the upper 

 margin of the head, or vertex, and below by a line drawn across 

 the base of the antennas, is called the front ; on the lower part of 

 the front, in most diptera cyclorrhapha, there is a crescentic space 

 (frontal lunole) separated by an impressed line. On the upper 

 part of the front, near the vertex, there are usually three, rarely 

 two, often no, simple, small eyes, called ocelli — their presence or 

 absence is an important character. In the holoptic male, the trian- 

 gle upon which these ocelli are situated, limited in front by the eyes, 



