340 



APPLIED ENTOMOLOGY 



The Hymenoptera are important from an economic standpoint. A 

 rather small number are injurious, destroying crops of various kinds 

 but the majority are either directly or indirectly beneficial, as parasites 

 of destructive insects, or by aiding in the fertilization of flowers, and in 

 the case of the honey bees by the value to man of their products. 



There is a great diversity of structure in the order, which has led 

 to the establishment of many families which fall into about 10 larger 

 divisions, generally called Superfamilies, and these may serve as the 

 basis for more detailed consideration. 



Superfamily Tenthredinoidea (The Saw-flies and Stem Borers). — 

 This group is one of the divisions of the Terebrantia as already described, 

 its members having no constriction of the abdomen. Most of the families 

 belonging here are leaf-feeders and their eggs are usually laid in slits in 

 the leaves sawed by the ovipositors of the adult females. Some families, 

 however, have the ovipositor constructed for boring and they make 

 holes, either in herbaceous or woody stems, in which to deposit their 

 eggs. 



The plant-feeders are spoken of in a general way as saw-flies and all 

 are injurious to the plants they live on, though of course many of these 



are of little or no importance to 

 man, but a few injure various 

 crop-producing plants. 



The Currant Worm (Pteronidea 

 ribesii Scop.). — This common in- 

 jurious saw-fly is a native of Europe 

 but has been in this country for 

 many years and is widely dis- 

 tributed. It feeds on the leaves 

 of wild and cultivated currants 

 and to some extent, on those of 

 gooseberries also, and when abund- 

 ant the plants are quickly and 

 thoroughly stripped of their foliage 

 soon after it develops, which checks or almost entirely prevents the 

 production of the fruit. 



The adult saw-fly (Fig. 355) is about a third of an inch long, with a 

 pale or reddish-yellow, rather stout body with blackish spots. It passes 

 the winter in the ground within an oval cocoon, rather papery in texture 

 and brown in color. In spring, about when the currant leaves become 

 partly developed, the adults begin to emerge from their cocoons and the 

 females lay their eggs in rows on the leaves, generally along the veins on 

 the underside. The larvae, at first very small and whitish, feed and grow 

 rapidly, and when full-grown are nearly three quarters of an inch long, 

 greenish in color and shaded with yellowish at both ends. During the 



Fig. 355. — Currant Worm {Pteronidea 

 ribesii Seop.), adult and larvae, about natural 

 size. {From Minn. Agr. Exp. Sta. Bull. 84.) 



