NATURAL HISTORY OF SOUTH AFRICA 



was stripped absolutely bare by the caterpillars of a 

 small moth (Tortix viridand) in the spring of 1905. 

 The neighbouring wood belonging to Baron von 

 Berlepsch was untouched. In this wood some years 

 previously over 2,000 nesting boxes had been affixed 

 to the trees. Dr Gordon Hewitt, D.Sc, in writing 

 on the subject, says : " It stood out among the 

 remaining woods like a green oasis." 



BIRDS AND HEALTH 



Birds are a strong factor in checking the onslaughts 

 of the disease microbe army. We now know that 

 the great majority of diseases which attack man and 

 beast are carried by insects. A blood-sucking fly 

 inoculates man with the parasites which cause sleeping 

 sickness. Other blood-sucking flies carry the germs 

 of a number of deadly diseases to stock animals, and 

 inoculate them direct by puncturing the skin with a 

 sharp lancet. The common house fly is one of the 

 foulest of feeders, and gets smothered with the bacteria 

 of various diseases, and also voids them alive from its 

 body. These germs it sows in our households and 

 amongst our domestic animals. The house fly is now 

 regarded as the chief cause of the spread of diseases 

 in human communities and to the various members of 

 households. 



The larva of a gad or warble fly produces 

 100 



