ADAPTIVE COLORATION 



2OI 



themselves must have been present, however, before natural selection 

 could begin to operate ; their origin is a question quite distinct from that 

 of their subsequent preservation. 



Protective Mimicry. This interesting and highly involved phe- 

 nomenon is a special form of protective resemblance in which one species 



PIG. 247. A, Anosia plexippus, the "model;" B, Basilarchia archippus, the "mimic." 



Natural size. 



imitates the appearance of another and better protected species, there- 

 by sharing its immunity from destruction. Though it attains its high- 

 est development in the tropics, mimicry is well illustrated in temperate 

 regions. A familiar example is furnished by Basilarchia archippus 

 (Fig. 247, B), which departs widely from the prevailing dark coloration 

 of its genus to imitate the milkweed butterfly, Anosia plexippus. The 

 latter species, or " model," appears to be unmolested by birds, and the 

 former species, or " mimic," is thought to secure the same exemption 



