RELATION TO ANIMAL KINGDOM 15 



that this intelligence is best manifested ; but I have noted 

 it in the majority of the species that I have observed at 

 all carefully in the open, under natural conditions rather 

 than in the laboratory in artificial surroundings. 



Insects are as a rule prolific breeders, although 

 there is a great difference between them in this respect: 

 some multiply only ten-fold in the course of the season, 

 while in others the capacity is 1,000,000,000 descendants 

 in the same period. No one has actually counted that 

 number, of course, but we have counted the number 

 born to a single pair and determined the number of 

 broods to the season; so it is a mathematical certainty, 

 even if, as a matter of fact, probably no one pair ever 

 matured all its offspring for as many successive genera- 

 tions as are required to produce such a result. 



In their development there is considerable variety, 

 but as a rule they pass through four more or less distinct 

 stages: this being called transformation or metamor- 

 phosis, while the various stages are also called instars. 



The first, or egg-stage, is usually quiescent and gen- 

 erally passed outside the insect body ; but in some cases 

 it hatches within the ovary of the mother and young are 

 born alive, as in many plant lice and scale insects. Spe- 

 cies may therefore be oviparous (egg-bearing), or vivip- 

 arous (live-bearing), the latter also termed larviparous. 



The second, or larval stage, is that which hatches 

 from the egg, and it may or may not be like the parent. 

 In the grasshopper, for instance, we can recognize it 

 as such, no matter how recently hatched; but in the 

 minute caterpillar, just out of the shell, no resemblance 

 to the butterfly can be traced. The larval stage is the 

 period of growth: the insect feeds to the limit of the 

 elasticity of its integument or outer skeleton, then 

 sheds this skin or "moults," and repeats this process 

 until it has reached its limit of size. 



