No. 2.] PROTECTIVE RESEMBLANCES IN SPIDERS. 75 



ing a trace behind. This recalls Prof. Wilder's suggestion that 

 the immense fertility of Nephila plumipes is counter-balanced 

 by the desti'uction of its cocoons, which are so placed, depend- 

 ing from leaves, that great numbers of them are washed away 

 and destroyed by rain. 



Let us look at the Attida;. In this family the most fertile 

 species on record is Phidippus morsitans, laying about 180 

 eggs ; while the least fertile is the little, ant-like Synageles 

 picata, laying three. 



So far as defending itself from the attacks of enemies of 

 its own class is concerned, morsitans has an unquestionable 

 advantage. It has not only superior agility ; it is also one of 

 the largest and fiercest of the family, and it is improbable that 

 any other spider preys upon it ; while nothing more defense- 

 less can be imagined than the little picata, with its tiny body, 

 weak falces and slender legs. The fierceness of morsitans, 

 however, would be useless agaiust such foes as birds and wasps, 

 while the strongly contrasted black and white of its coloration 

 make it conspicuous. 



Beyond the fact that it is small and dark-colored, picata 

 has absolutely nothing to protect it excepting the resemblance 

 which it bears to an ant. Can this alone gives the species so great 

 an advantage that it is enabled to maintain itself with as low a 

 birth-rate as three or four in a season ? 



"We must accept one of two alternatives. The direct 

 relation between mortality and multiplication is well estab- 

 lished, and it is plain that no species could maintain itself 

 with so low a birth-rate were not its mortality correspondingly 

 low. It must, then, either have practically no enemies, or its 

 means of protection from its enemies must be uncommonly 

 efficacious. We cannot accept the first alternative. No crea- 

 tures are exposed to the attacks of more enemies and none are 

 more helpless under such attacks than small, soft-bodied 

 spiders; and the conclusion seems unavoidable that picata 

 enjoys immunity from attack because it appears to be not a 

 spider but an ant. 



