294 



INSECTS INJURIOUS TO THE GRAPE. 



Fro. 305. 



an inch long and one-fourtli as wide, containing a solitary 

 orange-yellow larva, about one-eighth of an inch long. This 

 is also the larva of an undetermined species of Cecidomyia, 

 a family the members of which may be recognized in the 

 larval state by a peculiar appendage known as a breast-bone 

 attached to the under side near the head. In this species it 

 is almost Y-shnped, as shown at a in the figure; the diverging 



branches terminate in two pro- 

 jecting points, which may be 

 extended at will, and which are 

 probably used by the larv^a in 

 abrading the soft tissues of the 

 gall so as to cause an exudation 

 of sap, on which the larva feeds. 

 The flies belonging to this genus 

 are usually of a dull-black color, 

 like that shown in Fig. 305, a, 

 which represents a female fly ; the antenna of a male is seen 

 at b. The gall is common in July ; the larger-sized specimens 

 bear some resemblance to a bunch of filberts or hazel-nuts, 

 hence the name filbert-gall. 



No. 168. — The Grape-vine Tomato-gall. 



Vitis iomatos lliley. 



These galls form a mass of irregular, succulent swellings 

 on the stem and leaf-stalks of the grape-vine (see Fig. 306), 

 very variable in size and shape, from the single, round, cran- 

 berry-like swelling to the irregular, bulbous protuberances 

 which look much like a group of diminutive tomatoes. They 

 have a yellowish-green exterior, with rosy cheeks, and some- 

 times are entirely red; the interior is soft, juicy, and acid. 

 Each gall has several cells, as shown at a in the figure, and 

 in each cell there is an orange-yellow larva, which, before the 

 gall has entirely decayed, enters the ground, where it changes 

 to a chrysalis, and finally emerges as a pale-reddish gnat, with 

 black head and antennae, and gray wings. This fly also be- 



