128 IN THE GUIANA FOREST. 



us to study them carefully from every standpoint. 

 Nothing is too insignificant ; we must put on 

 record every little habit that shows the hereditary 

 tendencies, as well as those that go to prove that 

 they are being modified by environment. We 

 firmly believe that insects, like ourselves, make 

 experiments, the consequences of which, by 

 natural selection, become fixed as hereditary 

 instincts. They discover us, our domestic animals, 

 and our cultivated plants. Some will say that 

 possibly it is only a discovery, due to closer obser- 

 vation by ourselves, when we first meet a new 

 pest ; that it had long been there but hitherto we 

 had not seen it. Some may have been so, but 

 certainly not all. Our cultivated plants have been 

 carried off from their original habitats and all have 

 been discovered by insects which had not hitherto 

 seen them. 



In self-defence we must continue our war with 

 these plagues. No gardener, planter, or forester 

 can afford to ignore them. The cry is that they 

 are increasing everywhere, and quarantine is being 

 enforced in most countries. Notwithstanding all 

 our efforts, however, still they come. If outsiders 

 are excluded we cannot provide against our own. 

 Almost every year new pests come to the front 

 and must be studied. In some cases we have 



