132 The Classification of Insects 



between the two, and both can be derived from the 

 same parents (141). 



Species.— Where, on the other hand, two forms 

 differ from each other in some definite characters, 

 and no intermediate links are known connecting them, 

 they are said to be of distinct kinds or species. On 

 the same sunny English hillsides where Polyorumatus 

 astrarche is found, another commoner, larger and 

 more lively butterfly (fig. 83) may be observed. Its 

 eyes are covered with hairs, while those of astrarche 

 are naked. The under side of its forewing differs 

 from that of astrarche s in having two additional 





Fig. 83. — "Common lllue " Bulieriiy (Poiyamiuatus icarus). a. Male, upper 

 surface ; /'. under surface ; c. female, upper surface. Natural size. 



eye-spots near the root. In the female there is, as in 

 astrarche, a marginal row of orange spots on the 

 upper surface, which is brown, though dusted over 

 with bright blue scales. But the male of this second 

 kind shows no trace of orange spots on the upper 

 surface, which is of an uniform, beautiful lilac-blue. 

 This insect, then, though resembling astrarche in some 

 particulars, differs in a startling way in others. No 

 specimen of astrarche has ever been observed with 

 hairy eyes, with blue scales above, or with eye-spots 

 beneath the basal half of the forewing. Moreover, 



