130 IN THE GUIANA FOREST. 



them, especially the solitary kinds, are very useful 

 as they keep down other insects, many of which 

 are noxious. The same may be said of flies and 

 beetles ; the whole class must not be stigmatised as 

 plagues because of a few. 



Insects find out new plants and get away from 

 their enemies ; these also follow them after a time. 

 Meanwhile, however, the pest has got into snug 

 quarters where it gets better fed than its brethren 

 who have nothing but the hardy, protected trees 

 of the forest. For a time it flourishes to an 

 extent hitherto quite unknown. At last, however, 

 it may be many years after, their enemies discover 

 them. Now we get a grand fight. The pests have 

 increased to a wonderful extent but their foes are 

 upon them. Not one species but sometimes a 

 dozen or more. As many as thirty distinct 

 parasites have been seen coming from one kind of 

 hawk-moth. Now the pest diminishes, and later 

 the parasites, which had come to the front, get 

 fewer and fewer as their food becomes scarce. 

 Neither the pest nor its foes are, however, entirely 

 gone, they are only scotched. Presently the one 

 begins to recover and the agriculturist cries out 

 that the plague has come again. So it may go on 

 for ever, notwithstanding all man's efforts. We 

 may try our level best to put down some enemy 



