254 



ZOOLOGY 



Tomato worm and cocoons of ichneumons, 

 photograph by Overton. 



From 



structure, and can no longer work, but only fight. Some species 

 go further and make slaves of the ants preyed upon. These slaves 

 do all the work for their captors, even to making additions to their 

 nest and acting as nurses to their young. 



The entire communal life of the ants seems to be based upon 

 the perception of odor. If an ant of the same species but from a 



different nest be put 

 into another colony, it 

 will be set upon and 

 either driven out or 

 killed. Ants never 

 really lose their com- 

 munity odor ; those 

 absent for a long time, 

 on returning, will be 

 easily distinguished by 

 their odor, and eagerly 

 welcomed by the mem- 

 bers of the nest. The talking of ants (when they stop each other, 

 when away from the nest, to communicate) is evidently a process 

 of smelling, for they caress each other with the antennae, the 

 organs with which odors are 

 perceived. 



Ichneumons. — One of the 

 Hymenoptera (incorrectly 

 called a fly) , the ichneumon fly, 

 is of considerable importance, 

 because of its habit of laying 

 its eggs and rearing the 

 young in the bodies of cat- 

 erpillars which are harm- 

 ful to vegetation. Some of 

 the ichneumons even bore 

 into trees in order to de- 

 posit their eggs in the larVSe Thalessa boring in an ash tree to deposit its 



of WOOd-borina; insects. It ^^^^ ^'^ *^^ burrow of a hom-tail larva, a 



wood borer. From photograph, natural 

 IS safe to say that by the size, by Davison. 



