156 SCHOOL ENTOMOLOGY 



usually become more like caterpillars at their last molt. 

 They have six to eight pairs of pro-legs. Their food is 

 the foliage of plants. The slug-like forms have very short 

 legs and are covered with a slimy substance. They are 

 usually larger through the thoracic region and taper to- 

 ward the tip of the abdomen. Many saw-fly larvae have 

 the curious habit of curling the tip of the abdomen 

 forward and downward, often looping it partly around the 

 twig or the edge of the leaf upon which they rest. 



Important species of saw-flies are the Imported Cur- 

 rant-worm] the Pear-slug (see page 316, Part II), which 

 attacks pears and cherries, and skeletonizes their leaves, 

 causing them to turn brown and fall off; the Rose-slug, 

 similar to the pear-slug but smaller, and many species 

 attacking shade and forest trees. Slugs may easily be 

 killed with arsenate of lead or by dusting them with 

 almost any dust. 



103. Gall-flies. The gall-flies, Cynipoidea, form another 

 of the highly specialized and unusually interesting groups 

 which are found so frequently in this order. The adults are 

 almost all small, often with metallic colors. They have 

 the abdomen compressed laterally and somewhat tele- 

 scoped. It is not by the adults, which are at best in- 

 conspicuous, nor even by the larvae, but by the abnormal 

 growths which the larvae produce on plants, that our at- 

 attention is attracted to this group of insects. Many 

 dwellings are produced on plants by insects of other orders 

 and all are known as galls. Some are caused by Diptera, 

 the gall-gnats, some by small moths and many others 

 by plant lice, but the great majority of galls are pro- 

 duced by members of this family. They are found 

 on stems and leaves of oak, on hickory leaves, on rose 

 twigs, on blackberry canes and on other plants. In form 



