MANKIND AND THE INSECT 323 



hardest stone appear to daunt them. It is even said 

 that they can injure glass by the aid of their corrosive 

 saliva. Years ago a species of termite was accidentally 

 introduced into the island of St. Helena — in what manner 

 is not definitely known. It increased and multiplied to 

 such an extent that Jamestown was soon reduced virtually 

 to ruins, and new buildings had to be erected. In like 

 manner termites destroyed the Governor's palace at Cal- 

 cutta, and an English ship lying in Bombay harbour. 

 Wherever they pass they leave a trail of devastation. 

 Clothing, books, flour, and grain are quickly devoured, 

 while woodwork is rapidly reduced to a heap of powder 

 and chips. 



The various insect assailants of domestic animals are 

 a constant source of annoyance and loss. Gad-flies perse- 

 cute horses and cattle, and are believed in some instances 

 to infect them with disease. The bot-flies (CEstridce), as 

 we have seen, are actual parasites in their larval state, 

 feeding in the nasal passages, the stomach, or beneath the 

 skin of the host. The most serious are the warble-flies 

 (Hypoderma), which not only detract from the quality of 

 the beef, but also damage the hide by perforation. The 

 late Miss Ormerod estimated the loss in Great Britain 

 from these insects at £700,000 per annum in some years ; 

 and although this figure has now been much reduced, 

 owing to the measures adopted by farmers and graziers, 

 it is still very considerable. 



The most serious indictment made by science against 

 insects is that many species are active agents in the 

 dissemination of disease. Within the last fifty years, it 

 has been discovered that many diseases are caused by 

 microscopic parasites ; some, such as plague and typhoid 

 fever, by extremely minute vegetables known as bacteria ; 

 others, such as malaria and sleeping sickness, by almost 



