296 



INSECTS INJURIOUS TO THE GRAPE. 



Fig. 307. 



like that of a hazel-nut, to the stem of the vine. On its ex- 

 ternal surface there are longitudinal depressions, which divide 

 the gall into eigHt or nine segments. The interior is fleshy 

 for about one-eighth of its diameter, then follow a series of 

 elongated cells, each divided into tw^o by a transverse partition, 

 the lower being the shorter of the two. Fig. 307, a, represents 



the exterior of the 

 gall ; 6, a section of 

 the same, showing 

 its interior structure. 

 Each cell is occupied 

 by a single larva of 

 a bright-yellow color, 

 with a chestnut-brown, 

 Y-shaped breast-bone, 

 which eventually produces a gall-fly belonging to the genus 

 Cecidomyia. 



This gall sometimes varies in form, being occasionally flat- 

 tened or depressed ; when young it is downy on the outside, 

 succulent within, and is said to have a pleasant, acidulous 

 flavor. 



Should any of the galls described ever become a source of 

 annoyance, they may readily be destroyed by hand-picking. 



ATTACKING THE FEUIT. 



No. 170. — The Grape-seed Insect 



Isosoma vitis Saunders. 



This insect was first observed in 1868, when it threatened 

 to become a very troublesome enemy to grape-culture ; it was 

 widely distributed, and, having the fecundity usually charac- 

 teristic of insect life, it might have been expected to increase 

 immensely; but this happily has not been the case, and of 

 late it has seldom prevailed to any serious extent. 



