190 DIPTERA OF NORTH AMERICA. 



Lasioptera vitis 0. S. (See No. 23.) 

 On the golden rod (Solidago). 



C. solidaginis Lw. (See No. 9.) 



C. hirtipes 0. S. (See No. 10.) . 

 On Chrysopsis mariana. 



C. chrysopsidis Lw. (See No. 29.) 



In comparing this list with similar enumerations existing for 

 European Gecidomyiae, but few cases of analogy will be found. 

 Such cases are, for instance, the habits of G. pini inopis, nov. 

 sp., which correspond exactly to the European G. pini Degeer ; 

 the gall of G. strobiloldes, nov. sp., on the willow, which is repre- 

 sented in Europe by G. strobilana Bremi; the analogy between the 

 gall on Fraxinus americana (No. 18) and that of G. botularia Wz. 

 of the European ash, is more doubtful ; likewise that between the 

 deformation of G. erubescens, nov. sp. (No. 20) on the oak leaves, 

 and a similar deformation described by Mr. Loew (G. quercus Lw.) 



Two galls occur on the American wild grape, whereas none has 

 been discovered on the European grape ; likewise, although eight 

 galls are already known to occur on the hickory (Carya), none is 

 recorded as belonging to the European walnut (Juylans). Al- 

 though galls have been found on the European maple, alder, and 

 blackberry, they are different from those recorded below on the 

 American species of these trees and shrubs. Robinia, Lirioden- 

 dron, and in some degree Solidago, being peculiar to America, 

 their galls could not, of course, be expected to be found in Europe. 



I will proceed now to give a condensed description of the ob- 

 servations which I had occasion to make on Cecidomyia during 

 my residence in this country. These observations were made in 

 the environs of Washington, unless otherwise mentioned. I have 

 followed a practice adopted in Europe, in giving names to species 

 known only on account of the deformations they produce, the per- 

 fect insect not having as yet been reared. This affords. the advan- 

 tage of being able to designate each described gall by a fixed 

 name. In order, however, to distinguish such species from those 

 the gall-fly of which has been reared and described, the first are 

 simply put down as new species (n. sp.), whereas the names of the 

 authors have been mentioned after the specific names of the latter 

 (Lw. or O. S.) 



