1 6 INTRODUCTION. 



little crowd come round and make wondering 

 remarks at the muck which we are so care- 

 fully putting into the collecting-jar. To 

 them we are dabbling in filth. Not only the 

 ignorant, however, but even some educated 

 people, have a horror of insects. They 

 shudder at sight of harmless creatures and 

 even run off if a centipede or scorpion 

 is found when house-cleaning. If they 

 had been consulted when such pests came 

 into existence they would have given 

 strong opinions against their creation. 

 Fortunately for the world, and even for 

 themselves, greater wisdom was to the 

 fore. 



It may be safely stated that, apart from 

 man's interference, there are no unmitigated 

 pests. He himself is the great offender, 

 as Ray Lankester well says, " Nature's 

 insurgent son." But, continues Dr. Lan- 

 kester, he cannot escape from the con- 

 sequences of his actions. A successful 



