ROSE GALL-FLIES. 549 



them contains a single grub, and this in due time turns to 

 a gall-fly, which may be called Cynips bieolor, the two-col- 

 ored Cynips. Its head and thorax are black, and rough 

 with numerous little pits ; its hind body is polished, and, 

 with the legs, of a brownish-red color. It is a large insect 

 compared with the size of its gall, measuring nearly one 

 fifth of an inch in length, while the diameter of its gall, not 

 including the prickles, rarely exceeds three tenths of an 

 inch. 



Cynips dichlocerus, or the gall-fly with two-colored antennas, 

 (Plate VIII. Fig. 6, Fig. 7 magnified,) is of a brownish- 

 red or cinnamon color, with four little longitudinal grooves 

 on the top of the thorax, the lower part of the antennae red, 

 and the remainder black. It varies in being darker some- 

 times, and measures from one eighth to three sixteenths of 

 an inch in length. Great numbers of these gall-flies are 

 bred in the irregular woody galls, or long excrescences, of 

 the stems of rose-bushes (Plate VIII. Fig 8). 



The small roots of rose-bushes, and of other plants of the 

 same family, sometimes produce rounded, warty, and woody 

 knobs, inhabited by numerous gall-insects, which, in coming 

 out, pierce them with small holes on all sides. The winged 

 insects closely resemble the dark varieties of the preceding 

 species, in color, and in the little furrows on the thorax ; 

 but their legs are rather paler, and they do not measure 

 more than one tenth of an inch in length. This species has 

 been named Cynips semipiceus. 



Monstrous swellings of buds, and various other kinds of 

 excrescences, may often be seen on plants ; but my speci- 

 mens of the insects producing them are not in a condition 

 to be described. The foregoing account, however, will serve 

 to illustrate the habits of some of our most common gall- 

 flies, and explain the origin, forms, and structure of their 

 singular productions. Such excrescences, as soon as they 

 are observed on plants of any value, should immediately be 

 cut off, and put into the fire. 



