DESTRUCTIVE INSECTS. 21 



the entire consumption of the nation for a period of five weeks, 

 and two species alone are computed to consume annually more 

 than three millions of men. (D The celebrated curculios, and 

 the ' terrible ' Angoumois moth, so dreadfully destructive in 1760, 

 are among the wheat pests of France. 



22. (b) The progress and increase of insects destructive to 

 cultivated crops in the United States, is a subject of the utmost 

 importance to agriculture. So many threatening and uncon- 

 trollable circumstances govern their increase on this continent, 

 tlikt the danger of short harvests arising from their depredations 

 is year by year growing more imminent, and will some day come 

 upon the country with a blow as sudden as it will be terrible. 

 The immense area occupied by cultivated crops, the almost total 

 absence of rotation, and the remarkable character of some of the 

 indigenous insects which have already proved seriously destruc- 

 tive in the middle States of the Ohio and Mississippi valleys, all 

 threaten a calamity which will be felt from Maine to Mexico. 

 As I propose to enlarge upon this subject in a future chapter, 

 further remarks are at present unnecessary. (Chapter VIII. 

 On the cultivation of wheat in the United States.) 



23. The food of insects embraces the utmost variety the animal 

 and vegetable world can offer. Some species are restricted to 

 particular plants, and if these fail, the race may for a time dis- 

 appear. < 2 ) Insects appear to be the instruments designed to 

 arrest the excessive growth and increase of certain species of 

 plants, and it is probable that there is not a species of plant, 

 which does not furnish nutriment for one or more tribes of 

 insects, either in their larvae state or in their perfect condition, 

 whereby it is prevented from multiplying to the exclusion of 

 others. 



(1) M. Delamane. (2) Carpenter. 



