436 INSECTS INJURIOUS TO VEGETATION. 



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 semipiceiis. 



Monstrous swellings of buds, and various other kinds of 

 excrescences, may often be seen on plants ; but my specimens 

 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. 



Gall-insects, as already stated, are often destroyed by little 

 parasites belonging to the family Chalcidid^e ; and as these 

 are liable to be mistaken for the former, especially when coming 

 from the same gall, it may be well to point out the difference 

 between them. The four-winged gall-flies have rather long, 

 straight, threadlike, and ascending antennae; the fore wings 

 with a few veins, forming two triangular meshes, one of which 

 is very small, and situated near the middle of the wing, the 

 other mesh much larger, and near the base ; the hind body 

 roundish but laterally compressed; and the piercer spiral or 

 curved, and concealed. The Chalcidians have shorter, elbowed, 

 and drooping antennae, which are enlarged towards the end; 

 a single vein, running from the shoulder near the outer margin 

 of the fore wing, uniting with this margin near its middle, and 

 emitting thence, towards the disk of the wing, a short oblique 

 branch, which is enlarged or forked at the end; the hind body 

 generally oval, pointed at the end in the females, and provided 

 in this sex with a straight piercer, which is more or less visible 

 beneath, and prominent at the extremity. By means of their 

 piercers, the Chalcidians thrust their eggs into the galls made 



