264: C. E. Beecher — Origin and Significance of Spines. 



under the head of mimicry. If, by their resemblance in form, 

 color, or voice any characters are similar to characters present 

 in the surroundings of the animal, and afford a means of pro* 



tection or are useful, they may be considered as mimetic in the 

 broadest sense of the term. Mimicry is usually restricted to a 

 kind of special resemblance, and not to the cases of general 

 resemblance afforded by an animal without significant colors in 

 general harmony with its surroundings. 



The influence of mimicry in the production of spines can 

 only occur where the object mimicked is spiniform or spinose. 

 Apparently this is rather infrequent and of little real import- 

 ance as a factor of acanthogeny. 



Insects and spielers have furnished the greatest number and 

 variety of mimetic forms, both in their larval and adult condi- 

 tions, and naturally would be expected to furnish examples 

 of spines having mimetic significance. The object mim- 

 icked may be another species of insect or animal, in which 

 case, there is usually some offensive or defensive quality ren- 

 dering the resemblance useful to the mimicker ; or, the whole 

 or a portion of some plant or other object may be imitated, 

 tending to the more or less complete concealment of the mim- 

 icking insect. 



Satisfactory examples are not at hand, though doubtless 

 many occur in nature, and some have been described, but not 

 for the present purpose. A few will be cited here which seem 

 to conform to the requirements. 



47. 48. 



Figure 47. — Profile of a Spider (Ccerostris mitralis) on a twig mimicking a 

 spiny excrescence. (From Peckham, after Vinson.) 



Figure 48. The larva of the Early Thorn Moth (Selenia illunaria) resting on a 

 twig; showing mimicry of stem and spiniform processes. |. (After Poulton.) 



A Madagascar spider (Ccerostris mitralis) is described by 

 Elizabeth G. Peckham 56 as sitting motionless on a branch and 

 resembling a woody excrescence with projections or spiniform 

 processes, figure 47. Other spiny spiders of the Epeiridse 

 probably have similar protective mimetic features, as Epeira 

 spinea and Acrosoma arcuata. 



