340 SCIENCE FROM AN EASY CHAIR 



burrowed, reduced to fragments and powder. And this 

 warfare he has incessantly carried on with increasing 

 skill and knowledge from the earliest times of which we 

 have any record. 



The sparrow and the rat, of which there has lately 

 been much talk, are examples of fairly large, easily de- 

 tected enemies of this kind. The almost ultra-microscopic 

 bacteria similar to those which produce disease by 

 multiplying in the living body are examples of the most 

 minute living pests which injure man by causing sourness, 

 putrefaction, and destructive rot in his food and stores. 

 Every year civilised man is gaining greater knowledge 

 of these " ferment organisms," and vastly increased skill 

 in preserving his possessions, such as food and drink, 

 from the attacks of their ubiquitous swarms. Between 

 the larger depredators, such as birds and rats, and the 

 smallest, such as the microscopic bacteria and moulds 

 (to whom alone putrefaction is due, and without whom 

 it would never occur), there are a host of small trouble- 

 some creatures, which belong chiefly to the group of 

 animals called " insects " beetles, moths, flies, and bugs 

 which give man incessant occupation in warding off their 

 attacks upon his food, his clothes, his furniture, his build- 

 ings, his crops and fruit trees, and his domesticated 

 animals. The study of these things and of the means 

 of grappling with them is the fascinating occupation of 

 those who are called " economic " zoologists and botanists. 

 Of course, in order to carry on their inquiries successfully 

 they have to bring to bear on the questions they investi- 

 gate as complete and thorough a knowledge as possible 

 of all the kinds of animals and plants, and of their ways 

 of feeding, reproducing, and protecting themselves in 

 natural conditions. 



One of the most widely celebrated and anciently 

 detested of insect pests is the clothes moth. It is the 



