INTRODUCTION. XXVII 



this creature should do this mischief particularly at 

 the present time ; and the answer at once is, that there 

 is a preternatural abundance of these creatures. If we 

 search historical records, we find that insects are very 

 prone to assume these periodic multitudinous appear- 

 ances ; and what is most strange is, that they almost 

 totally disappear between the times of their occur- 

 rence. 



All these facts I have fully described, and have 

 thus proved unquestionably and beyond a doubt that 

 the vastator is the cause of the present disease in the 

 potatoe plant ; that it is also the cause of the present 

 disease amongst various other plants ; that it is like 

 all other Aphides in its destructive character ; and, 

 lastly, that the preternatural appearance of insects 

 is, and has been, a common and universally known 

 fact from the earliest ages. 



