THE ORIENTAL MIGRATION. 267 



Clouded-Yellows in Western Europe, and both of 

 them must have come with this migration. 



A very good example of an Oriental migrant is 

 Danais clirysippus, a magnificent butterfly found in 

 Greece and Southern Italy. In Asia it is known from 

 Syria, Persia, and from the whole of the southern 

 portion of the Continent. The genus Danais (in 

 its wide sense) is a large one, and principally 

 occurs in the warmer regions of Asia. Three 

 species are found in North America and only one in 

 Europe. 



Among the beetles belonging to this migration, 

 there is one of very considerable interest from a dis- 

 tributional point of view, for all the species of the 

 genus even the whole family to which the genus 

 belongs are what is known by zoologists as " Com- 

 mensalists." These are animals habitually associating 

 and living in close connection with others with which 

 they are not tied by any family relations or kinship. 

 Such a state of close and permanent friendship is 

 called " commensalism." Now it appears as if the 

 members of this family of beetles (Clavigeridce) had of 

 their own free will formed such a close connection 

 with colonies of ants sometimes with one species, 

 sometimes another. They are the permanent guests 

 of the ants, and in return they secrete a fluid which is 

 apparently highly prized by them. All of the Clavi- 

 gers are provided with peculiar club-shaped antennae, 

 with which they ungraciously beat their hosts, when 

 they are in want of food. According to some authori- 



