IN CATERPILLARS 159 



(Papilio polyxenes), the more striking of the other 

 two mentioned, as in any sense protective, it is 

 nevertheless true, as pointed out by Poulton with 

 regard to the similarly colored species, the Swallow- 

 tail of Europe (P. machaon), that the protection 

 afforded by the coloring of these insects is " very 

 real when the larva is on the plant, and can hardly 

 be appreciated at all when the two are apart." 



Poidton, therefore, distinguishes between gen- 

 eral protective mimicry, which, he says, is '^ such 

 an appearance in an organism that the artistic 

 effect of its surroundings is sufficiently reproduced 

 in it to prevent attention from being attracted 

 when the one is seen in the midst of the other," 

 in fact simply a general harmony with its sur- 

 roundings ; and special protective mimicry, where 

 protection is gained by the acquisition of a special 

 appearance. Slater has urged that gaily colored 

 protected caterpillars feed upon poisonous plants 

 like Euphorbiaceae, Asclepiadaceae, Aristolochia, 

 etc. ; perhaps experimentation might show how 

 much value there is in this suggestion. 



One further point may be alluded to. It is 

 well known that the caterpillars of many species 

 of Lepidoptera are dichromatic in their later life, 

 some of the forms being brown and others green. 



