CHAPTER XV 

 MIGRATION 



AT times, mainly at certain seasons of the year, a strange 

 restlessness overcomes animals and they change their 

 quarters for some more congenial spot. This wandering 

 from one part of the earth to another is termed migration. 

 Insects, birds, mammals and even fishes are all victims of 

 this craving for new fields, but the habit reaches its zenith 

 amongst the birds. It is hard to define exactly when 

 migration begins and when it ends. The chicken which 

 leaves its home farm and joins its neighbours of the next 

 poultry yard, migrates ; the fox which, maybe through too 

 persistent attention on the part of the local hunt, seeks 

 another earth, migrates ; but for our purpose migration 

 implies a regular organised movement from one country to 

 another, or at least from one end of a country to another. 

 Amongst insects, migration does not appear to be 

 a fixed habit, except in a few cases. The wholesale 

 wanderings of the processionary moth larvae cannot, 

 strictly speaking, be termed migration. In South Europe 

 we have seen hordes of cockchafers descend upon a 

 district, destroying the vegetation far and wide, and there 

 are well-authenticated cases of migration amongst certain 

 species of butterflies. But all these are not regular 

 periodical movements ; they are merely occasional wander- 

 ings and, as such, do not come under our definition of 

 migration. Of all insects there are none with migratory 

 habits so highly developed as the locusts ; one species, in 

 fact, is called the migratory locust. These migrations 

 have a great influence on the inhabitants. 



The locusts appear in vast swarms, and eat up every scrap 

 of vegetation, till nothing green remains in the land for 



