INSECTS INJURIOUS TO THE BLACKBERRY. 



ATTACKING THE CANES. 



No. 186.— The Pithy Gall of the Blackberry. 

 This curious gall, which is represented in Fig. 332, is some- 

 times found on blackberry canes. It is about two or three 



inches long, of a dark- 

 red or reddish-brown 

 color, oblong in form, 

 with its surface un- 

 even, with deep lon- 

 gitudinal furrows, 

 which divide the gall 

 more or less com- 

 pletely into four or 

 ■^J,% five portions. It is 

 caused by a small 

 four-winged fly, Di- 

 astrophus nebulosus 

 Osten Sacken. If a 

 transverse section of 

 this gall be made, 

 there will be found 

 about the middle a 

 number of oblong 

 :ells about one-eighth 

 of an inch long, 

 shown at b in the 

 figure, each contain- 

 ing a single larva or 

 pupa. Hie larva, which is represented enlarged at c, is about 

 one-tenth of an inch long, white, with the mouth p^rts 

 318 



