HYMENOPTERA 



245 



number of prolegs on the abdomen, and lack the hard shield usually 



found on the prothorax 

 of lepidopterous cater- 

 pillars. Most of them 

 feed on foliage, and many 

 are quite injurious. Sev- 

 eral species are soft- 

 bodied and covered with 

 a viscid, slimy matter, 

 which has given them 

 the name of ' slugs." 

 Among the more com- 

 mon species are the 

 yellow-and-green currant 

 worms (Xcwatiis ribe- 

 sii), which devour the 

 foliage of currants and 

 gooseberries, the rose- 

 slug (Monostegia rosae], 

 w<hich strips off the sur- 

 face of rose leaves, leaving them brown as if scorched, and the 

 pear-slug (Eriocampa ce- 

 rasi), which injures pear 

 and cherry foliage in the 

 same manner. Other spe- 

 cies often defoliate straw- 

 berry and raspberry bushes, 

 and there are numerous 

 species which may be 

 found on various shade 

 and forest trees, one of 

 the most injurious being 

 the larch saw-fly (Ly- 

 gaeonemcttus erichsonii) , 



" v *> 



FIG. 386. The pear-slug 



ft, adult saw-fly, female ; />, larva with slime removed ; 



c, same in normal state ; d, leaves with larva (natural 



size), (a, b, c, much enlarged.) (After Marlatt, United 



States Department of Agriculture) 



which has defoliated and 

 thus destroyed large areas 

 of larch in New England 

 and Canada. 



FIG. 387. Pear-slug, illustrating method of ovi- 

 position and emergence of larva. (Enlarged) 



a, cutting of cell beneath epidermis of leaf, showing 

 the tip of the ovipositor : 6, the cell after the egg 

 has been deposited ; c, same after the escape of the 

 larva. (After Marlatt, United States Department of 

 Agriculture) 



