4 POPULAR EIJTTOMOLOGY. 



of various forms^ and are divided into two principal classes — 

 those having a distinct scaly liead^ including many of our 

 principal insects^ and those without a distinct head^ as the 

 majority of the two-winged Mies ; the minor distinctions 

 depend principally on the number of the legs and prolegs, 

 but for these the student must refer to larger works. Hav- 

 ing attained its full size after several times changing the skin, 

 the larva undergoes its final and most important transfor- 

 mation, appearing in quite a different shape, that of the ptipa, 

 during the period of which it remains more or less inactive, 

 and would be liable to destruction were it not for the ad- 

 mirable instinct sliov/n by the larva in preparing for the 

 new state of existence to wliicli it is destined. Here again 

 the distinctions are too multiplied to be fully entered into 

 in so slight a sketch as the present, tliougli the whole may 

 be classed under two heads — those wliose transformation is 

 partial, and those in which it is complete. Linnasus divided 

 them into five kinds, as follows : — 



Ftcpa co?]zpleta, active, with all the parts of the perfect 

 insect : example, Aranea, the Spider. 



Pttjoa semi-completaj active, resembling the parent, but 

 having only the rudiments of wings : example, Grylhis, the 

 Grasshopper. 



