OF WASHINGTON. 89 



a basis and guide for future exploration of a certain region, 

 and to be a contribution to our knowledge of geographical 

 distribution of insects. 



Mr. Howard stated that in the Hymenoptera Prof. Smith 

 had largely followed Cresson's Catalogue, and had included 

 as from New Jersey those species against which Cresson has 

 placed "U. S." In many cases Cresson, however, has re 

 corded the United States as the habitat of species only actually 

 found in two or three rather widely separated localities, so that 

 to record, such species as from New Jersey is very rash. 

 Moreover, among the parasitic Hymenoptera both Cresson and 

 Smith seem to have taken it for granted that where a parasite 

 has been bred from a host, its geographical range is the same 

 as that of the host insect. The fallacy of this is shown in the 

 fact that Cresson catalogues Euplectrus comstockii Howard, a 

 common parasite of Aletia xylina Say, as from " U. S.," and 

 Smith consequently catalogues it from "N. J.," whereas this 

 parasite occurs only, so far as we know, in the breeding region 

 of Aletia, viz : the southern States. 



Mr. Townsend presented the following paper : 



THE NORTH AMERICAN GENERA OF CALYPTRATE 

 MUSCID^E. 



PAPER i. 

 BY C. H. TYLER TOWNSEND. 



The super-family name MUSCINA may be used with much 

 propriety to designate the whole natural division of the 

 Diptera comprehended in the term Muscidtz sens. lat. This 

 division has long been divided, for convenience sake, into two 

 great sections : the Muscidce caly pirates (also written calyptertz), 

 as opposed to the M. acaly >ptrat<z . The former are commonly 

 supposed to be distinguished from the latter by the possession 

 of large and well developed tegulse, which in the acaly ptrat& 

 are defined as rudimentary or absent. In reality, however, no 

 true line of separation can be drawn ; for, as Mr. van der 

 Wulp very aptly remarks, ' ' when the numerous species are 

 examined, the tegulse are found to decrease gradually in size 

 till they finally disappear altogether" (Biol. Cenrr.-Amer. ; 

 Dipt., II, p. 2). It was thought at one time that another 



