14 PRACTICAL ZOOLOGY. 



a. The egg. 



I. The larva, at different stages of growth; keep 

 one worm in a cage by itself, and make a draw- 

 ing every third day. 



c. The pupa, showing how it is suspended. 



d. The perfect butterfly. 



3. The cabbage butterfly belongs to the family Papilion- 

 idae, genus Pieris, species rapae. 



There are several species of the genus Pieris, just as 

 there may be several in one family among us ; as in a 

 directory we read : " Smith, Charles," " Smith, Edmund " ; 

 so we read : Pieris rapae ; Pieris protodice. 



What is the meaning of the word " rapae " ? 



For account of the cabbage butterfly, see " Report of the 

 Entomologist" in the "Report of the Commissioner of 

 Agriculture for the year 1870." 



Occasionally a larva will fail to go through its proper 

 changes; this is generally caused by some parasite, the 

 most common of which is an ichneumon larva. The adult 

 of some kind of ichneumon fly stings the cabbage worm 

 and lays its eggs in its body ; these eggs hatch out as 

 worms and live on the juices and tissues of the cabbage 

 worm, till it dies from exhaustion (though the cabbage 

 worm often lingers, and the parasitic larvae complete their 

 transformation first), and the parasitic larvae become pupae, 

 and hatch out as perfect ichneumon flies. 



Look for holes in pupae which fail to complete their 

 transformation ; often holes may be found in them where 

 the ichneumon flies have made their escape. If a pupa 

 blacker than usual be found, put it in a vial, or pill box, 

 and catch the ichneumon flies as they emerge. 



