ICHNEUMON FLIES. 129 



166, larva of Tremex coluniba), whose fleshy white larvae 

 bore ill trees. The adults are large, with a long, saw-like 

 ovipositor. In the saw-flies {TenthredinidcB, Fig. 167 the 

 pear-slug, Selandria cerasi) the larva strongly resembles a 

 caterpillar, having eight pairs of abdominal feet. 



The gall-flies (Fig. 168, Cijnips) are small Hymenoptera 

 which lay eggs in the leaves or stems of the oak, etc.,; 



Fia. 170. — CEcodoma, or Leaf -cutter Ant of Nicaragua. 



which, from the irritation set up by their presence, causes 

 the swelling termed a gall. 



The ichneumon-flies (Fig. 169) are very numerous in 

 species and individuals; by their ovipositor, often very 

 long, they pierce the bodies of caterpillars, inserting sev- 

 eral or many eggs into them; the larvffi feed only on the 

 fatty tissues of their host, but this usually causes the death 

 of the caterpillar before its transformation. 



The family of ants is remarkable for the complexity of 



