OHAPTEE XIII. 

 ENEMIES AND THEIR INFLUENCE ON HABIT. 



WE have considered the means by which maternal instinct secures the 

 life and growth of the spider young. It is necessary to study the natural 

 methods by which excessive reproduction is held in check, for Nature 

 presents to the observer a more or less continuous series of favoring and 

 adverse circumstances, a " balance of power," so to speak, by which on one 

 hand life is protected, and on the other is devoted to destruction. In 

 each case there is equal regard for the common good and the general har- 

 mony of Nature. 



I. 



The perils which beset the spider are many, serious, and diversified. 

 They besiege the very gate of being and cease not their relentless vigil 

 until the coveted life has been yielded. The " natural death " 

 fi ^p 31 '1 ^ ^ e aranea d i g a violent one ; comparatively few spiders, per- 

 haps, outside of those mothers who perish from inanition shortly 

 after the act of cocooning, have any other. It is this fact which compels 

 the great fecundity of the female, inasmuch as otherwise the species could 

 not be preserved. 



It is possible for one to conceive how the protective habits which have 

 been heretofore described might have gradually resulted from the mother's 

 struggle with her own enemies and those of her progeny. But. it is far 

 otherwise when one asks, could this struggle have so reacted upon the 

 structure of the animal as to thus modify its organs of reproduction ? If 

 no other obstacle presented, there would remain the seemingly insurmount- 

 able difficulty of accounting for the continuance of the species at all dur- 

 ing the long interval required for the supposed adjustment of the organs. 

 However that "may be, we shall see that there is need for all the eggs laid 

 and young hatched, and all the protective instincts and industries by which 

 these ends are secured. 



There is, of course, more or less irregularity in the operation of un- 

 friendly agents, which are themselves subject to laws of variation. In such 

 case there is a corresponding variation in the security of the species, and 

 so of their increase. The effects of a season unfavorable to spiders or 

 favorable to the growth of some enemy, or, on the contrary, advantageous 



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