308 Studies in the Theory of Descent. 



V. 



BIOLOGICAL VALUE OF SPECIAL MARKINGS. 



THE following questions now present them- 

 selves : Have the markings of caterpillars any 

 biological value, or are they in a measure only 

 sports of nature ? Can they be considered as 

 partially or entirely the result of natural selection, 

 or has this agency had no share in their produc- 

 tion ? 



The problem here offers itself more distinctly 

 than in any other group of living forms, because 

 it presents an alternative without a third possi- 

 bility. In other words, if it is not possible to 

 show that larval markings have a distinct biological 

 significance, there remains only for their explana- 

 tion the assumption of a phyletic force, since the 

 direct action of the environment is insufficient 

 to account for such regularity of development 

 throughout a series of forms. The explanation by 

 sexual selection is excluded ad initio, since we are 

 here concerned with larvae, and not with reproduc- 

 tive forms. 1 



1 [In 1879 Mr. George Francis, of Adelaide, forwarded from 

 the latter place a number of moths (a species of Anapaa) 



