RASPBERRY, BLACKBERRY AND DEWBERRY INSECTS 317 



References 

 Me. Agr. Exp. Sta. Kept, for 1892, pp. 133-146. 1893. 

 Col. Agr. Exp. Sta. Bull. 152. 1909. 

 U. S. Bur. Ent. Giro. 166. 1913. 



The Blackberry Leaf-miner 



Metalhis ruhi Forbes 



The leaves of blackberries and dewberries are often injured 

 to a considerable extent in the Eastern states and Canada 

 from Delaware and 

 Missouri northward 

 by the larva of a 

 small, nearly black 

 sawfly, about J inch 

 in length (Fig. 274). 

 The larvae feed be- 

 tween the two layers 

 of the leaf, excavat- 

 ing a rather large, 

 irregular blotched 

 mine ; three or four 

 mines may occur in 

 a single leaf (Fig. 



276). The injured portion of the leaf turns brown and dies; 

 in severe cases the whole field has the appearance of having been 

 singed by fire. 



The adults appear in late May or early June, and the female 

 inserts her white, flattened egg into the tissue of the leaf through 

 a puncture in the upper surface (Fig. 277). The egg lies next 

 to the lower epidermis Ix^neath a low blister about -3V inch in 

 diameter. At the time of hatching the larva has a very large 

 head in proportion to its size. When full-grown it is about 

 \ inch in length, and greenish-white in color with brownish 

 markings (Fig. 275). 



Fig. 274. 



The blackberry leaf-miner, adult. En- 

 larged. 



