ABSTRACT
Many noxious insects which used to live only in some one comparatively small region have been unintentionally transported by man to new environments where they have done immense damage. Many noxious insects which used to live only in some one comparatively small region have been unintentionally transported by man to new environments where they have done immense damage. Travel and trade are useful to insects as well as to micro-organisms. Yellow fever formerly existed only in West Africa, but was carried to the Western hemisphere by the slave trade. Owing to the opening up of Africa, it is gradually travelling eastward across that continent. When it reaches the east coast it will become almost impossible to keep it out of India and China, where it may be expected to halve the population. Sleeping sickness is an even more deadly African disease which is gradually spreading.
