THEIR RELATION TO PLANTS 77 



makers, largely on willow, the excrescences being 

 quite characteristic. 



The "horn-tails" have the ovipositor modified into 

 an augur-like process for making holes in plant tissue, 

 and the larvae are mostly borers: some in wood, most 



FIG. 31. The currant worm: a, adults; b, larvae in various stages of devel- 

 opment; c, pupa; e, eggs along veins on leaf. 



of them in shrubs or grasses. These very often threaten 

 the life of the plant attacked, especially when wheat or 

 other grasses are infested. But on the whole the number 

 of these boring species is small, nor are they often 

 numerous in examples. 



A very characteristic set of species is found in the 

 "gall- wasps" or Cynipids now ranked as a superfamily 



