372 



AN ECONOMIC ENTOMOLOGY. 



Fig. 428. 



tion of the body around the edge of the leaf or twig while feed- 

 ing. This is quite a characteristic peculiarity, and there is rarely 

 excuse for mistaking the larva of a saw-fly for that of a Lepidop- 

 teron, even without counting the prolegs. Many of these larvae 

 are injurious to cultivated plants, and some of them are known to 

 farmers as "slugs" or "worms;" for instance, we have the 

 "currant-worm," the "grape-slug," the "rose-slug," and the 

 " pear-slug." When these larvae are full-grown they form thin, 

 tough, parchment-like cocoons, in which they change to pupae, 

 sometimes on the plant on which they feed, sometimes a little 

 below the surface of the ground. 



Perhaps none of the members of this family are better known 

 than the "currant-worm," or "slug," Nematus ribesii, which is 

 an imported insect, and annually does great injury where its food 

 plant is raised on a large scale. The flies, which are easily dis- 

 tinguishable by a rather deep yellow body, may be seen sitting 

 upon the foliage, or flying about heavily as 

 soon as the leaves of the currants are toler- 

 ably well developed in spring, and we may, 

 even at that time, find on the under sides, 

 arranged along the veins, series of little 

 white eggs laid by them. The larvae soon 

 make their appearance and feed ravenously, 

 frequently stripping a bush completely in 

 the course of a few days. I have seen rows 

 of currants covering an acre or more almost 

 entirely devoid of leaves and the fruit hang- 

 ing to bare twigs. There are two or three 

 broods in the course of a season, depending 

 upon latitude, the latter rarely as abundant 

 as the first and second, and practically not 

 nearly so destructive. The larva is green, 

 dotted with black, and nearly an inch in 

 length. 



On pears we frequently note a very dark green slug, the lar\'a 

 of Eriocaytipa cerasi, which is more or less slimy to the touch. 

 On young trees this sometimes does much injury by scraping 

 the upper side of the foliage until it dries and withers, falling to 

 the ground in midsummer. 



Pear-slug, larva of Etio- 

 campa cerasi. 



