50 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



But excluding the idea of intentional deceit, the mimicry of Ornithosca- 



toi'des has been explained as a product of evolution through natural selection 



and survival of the fittest. The explanation implies that the 



Evolu- existence of those individuals practicing the mimicry at first and 



* n accidentally had been preserved by the greater abundance of food 



or other advantage gained thereby, until it became a permanent 



habit. But we have only an inference that the habit is permanent in 



Ornithoscatoi'des. The facts recorded by Mr. Forbes stand entirely alone, 



and it seems more likely than otherwise that an extended observation of 



that spider would show that the same condition obtains as to its habits 



that we have observed .in Misumena, and that it will be found to spin a 



web substantially as described by Mr. Forbes, in many positions which 



would preclude the supposition of usefulness through resemblance to the 



excreta of birds ; as, for example, on the under side of leaves, underneath 



limbs of trees, between and under stones, hedges, etc. 



As to Misumena, we know that the case reported by Mr. Webster is abso- 

 lutely unique as yet ; knowing somewhat the general economy of this species 

 we can confidently affirm that the incident is exceptional. Misu- 

 Phe Mim- mena spreads her cocoon nest in. various positions, and is by no 

 icry x means ]j m ited to such locations as described by Professor Web- 

 ster. One of these positions has been described and figured in 

 Vol. II., page 152, Fig. 188. The general form of the cocoon nest is as 

 there exhibited, and in choosing the site thereof the mother appears to 

 give herself as wide range as do other species of the order. In other words, 

 she puts her cocoon and the nesting tube surrounding it in such place as 

 is most convenient to herself when the maternal function urges her to action. 

 The spinningwork described by Mr. Forbes 1 take to be the cocoon nest 

 of Ornithoscatoi'des, for it is not the habit of the Laterigrades generally to 

 get their food by means of snares. They belong to the Wandering group 

 of spiders, and stalk their prey along shrubbery, branches of trees, rocks, 

 walls, etc. If this inference be correct, the peculiar web observed by Mr. 

 Forbes is limited to the cocooning period, at which time Laterigrade spiders 

 are usually found within or lurking around the little tent which overspins 

 their egg sac. It must follow that the effect of industrial mimicry upon 

 the preservation of that species must have been confined to a brief period 

 at the end of the spider's life. To account for such mimicry as a product 

 of the survival of the fittest through natural selection, one needs to con- 

 ceive of the selection as operative in the early and most impressible stages, 

 or at least during the active period of life, and not during the few days 

 immediately preceding death. 



IV. 



In the second volume of this work (Vol. II., page 340) I ventured to 

 express a suspicion, which I have sometimes entertained, that the color 

 surroundings of the spider, in some manner not now explicable, may so 



