THE ORIGIN OF SPECIES 



Figure 93. A Masking Crab, Loxorhynchus crispatus. ( From Ricketts and Cal- 

 vin, "Between Pacific Tides," 2nd Ed., Stanford University Press, 1952.) 



poisonous snakes are brilliantly colored, and it may be that these are 

 properly interpreted as aposematic. In general, the Amphibia are crypti- 

 cally colored, but some have brilliant aposematic patterns (Figure 94). 

 These, of which Triturus torosiis, the western water-dog, is a good ex- 

 ample, are well supplied with poisonous skin glands. Many of the most 

 brilliantly colored insects are believed to have repugnant tastes (butter- 

 flies), while others have stings (bees) or emit foul-smelling fluids (coc- 

 cinellid beetles). 



Mimicry. Finally, there are the much disputed cases of mimicry. The 

 basic situation here is aposematism in which the same pattern ( or closely 

 similar patterns) is shared by two or more species. In the original descrip- 

 tion, Bates assumed that one of the species, the model, is genuinely apose- 

 matic, and appropriately marked; while the other species, the mimic, is 

 desirable prey, but shares the protection of the model by assuming its 

 cloak. This is known as Batesian mimicry. Miiller later described what 

 appeared to be an exceptional case of mimicry in which both the model 

 and the mimic appeared to be protected because of repugnance to preda- 

 tors. This type of mimicry, by wliich two or more species present a single 

 aposematic pattern for their predators to learn, is called Miillerian mim- 

 icry. It now appears to be much more common than Batesian mimicry. It 

 presumably operates as a kind of double insurance. 



244 



