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 Linnæus, 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 brassicæ (the larger) and Pieris rapæ (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 butterflies 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 urticæ; the peacock, Vanessa Io; the painted lady, Vanessa cardui; the red admiral, Vanessa Atalanta; and the comma butterfly, Vanessa C-album. There are other European, Asiatic, and American species of Vanessa.