WHAT IS MEANT BY "A SPECIES"? 97 



now every year an increasing uniformity and agreement 

 among naturalists about the exact name to be applied to 

 every species of living thing. 



Returning to our collections of butterflies and meadow 

 flowers, we may take the names of some of the species and 

 genera as an example of the system of naming in use by 

 scientific naturalists. The common swallow-tail is assigned 

 to the genus Papilio. Its "specific name" is " Machaon," 

 given to it by Linnaeus, hence it is spoken of as Papilio 

 Machaon. It is found in various parts of Europe as 

 well as in England. But in Central Europe (often 

 seen in Switzerland) there is also another species of 

 swallow-tail, which only occurs as a rare accident in 

 England. This is the pale swallow-tail, differing, not only 

 by its paler colour but by definite spots and markings of 

 the wings, from the English species. Its species name, 

 or " specific name," is " Podalirius," and so it is known 

 as Papilio Podalirius. Species of Papilio are found all 

 over the world ; more than 500 are known. Our two 

 commonest whites belong to the genus Pieris — they are 

 called respectively Pieris brassicae (the larger) and Pieris 

 rapae (the smaller). The green-veined white is Pieris napi. 

 Each of these three is called after the plant, cabbage, 

 rape, or turnip, on which its caterpillar feeds. The rare 

 Bath white is Pieris daplidice. Its caterpillar feeds on 

 mignonette. There are dozens of species in other parts 

 of the world allied to our " whites," which naturalists have 

 carefully distinguished and characterized by their marks. 



Several of our most beautiful species of English butter- 

 flies which are much alike have been enrolled in one 

 genus — the genus Vanessa. This genus includes the great 

 tortoise-shell, called Vanessa polychloros; the smaller 

 tortoise-shell, Vanessa urticae ; the peacock, Vanessa Io ; 

 the painted lady, Vanessa cardui ; the red admiral, 

 Vanessa Atalanta ; and the comma butterfly, Vanessa 

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