1921 ENTOMOLOGICAL SOCIETY. 55 



established between them. Any disturbance or sudden reduction in the numbers 

 of the birds of a region is sure to disturb the balance in the insect world and 

 cause much loss to the crops upon which the insects feed. 



Moreover, the number of carnivorous animals bears a definite proportion 

 to the herbivorous animals upon which they feed, the herbivorous animals to 

 the plants, the plants to insect visitors, etc. In this web of nature we may note 

 that the animals preyed upon are more prolific than the predaceous forms. 

 "Small rodents tend to be much more prolific than carnivores. The primary 

 reason for this is probably that less individuated types tend to be more prolific." 

 — (Thomson). 



Sometimes man interferes with the balance of nature and serious conse- 

 quences follow. Rats became a great plague in Jamaica, and to offset them 

 the mongoose, a weasel-like animal, was introduced. The mongoose made short 

 work of the rats, but it turned its attention to useful animals such as poultry, 

 ground-birds and insect-eating lizards and snakes. As a result injurious insects 

 and ticks have increased greatly, and 'both plants and animals have suffered 

 much injury. 



Facts which convince even the most sceptical are accumulating regarding 

 the valuable role played by birds in the control of noxious insects. Studies of 

 bird diets prove conclusively that the majority of our common birds feed mainly 

 upon insects. Forbes of Illinois states after a careful study of the contents of 

 the stomachs: of birds that about two-thirds of the food of birds consists of insects. 

 Well-informed writers tell us that without birds the earth would be uninhabitable 

 after six years, and yet man in his ignorance is constantly destroying these 

 valuable friends, simply because he finds that they levy an insignificant toll on 

 his fruits and grains. It is possible that we would be better off if certain birds 

 were greatly reduced in numbers, but of this Ave are not absolutely certain, for 

 the web of life is most complex, and no person knows how far-reaching the results 

 would be. 



Aside from the fact that birds aid very materially in reducing the numbers 

 of insects when they come as scourges,, it is very important to remember that 

 birds nip many incipient scourges in the bud. Their mobility and varied character 

 and habits enable them to move rapidly from place to place and thus maintain 

 the balance of nature which man is always tending to upset. Even in wild nature 

 the balance is never quite complete ; at best the equilibrium is unstable. 



"It is very interesting that the two great classes of successful fliers should 

 be, in the wide economics of nature, pitted against one another, wings against 

 wings, freeman against freelrrian, invertebrate against -vertebrate, 'little brain' 

 against 'big brain,' 'instinct' against 'intelligence.' Practically this is the most 

 important conflict of classes that the world knows/' — (Thomson). 



It is worthy of note that the Italian entomologists do not share the opinion 

 of American and British fellow-workers as to the great value of birds in the 

 control of insect life. 



From 1850 to 1873, Rondani, an Italian, made most valuable contributions 

 to the study of parasitology. He was of the opinion, however, that parasites 

 were far more important than birds as control factors. He said: "The policing 

 of the fields cannot be entrusted to birds because they are unreliable and kill 

 the guilty with the innocent; they are robbers as well as guardians of the field 



