IOO AN INTRODUCTION TO ENTOMOLOGY. 



the North, the species winters in the egg state, and does not become 

 fully developed till the latter part of summer or in the autumn. A 

 few adults survive the winter ; and we have a few species in which 

 the eggs hatch in the autumn, and the insects pass the winter in the 

 nymph state. 



Many of the Acrididae never acquire fully developed wings ; the 

 way in which these short-winged adults can be distinguished from 

 nymphs has been given in the generalizations regarding the order. 



The locusts, or grasshoppers as they are commonly called, are of 

 first-class importance when viewed from an economic standpoint. 

 They feed on all kinds of vegetation, and they abound every year 

 in all parts of our country. Owing to their uniform abundance, 

 they have fallen into the category of the commonplace, and little is 

 said about them. I do not refer here to the migratory species, the 

 incursions of which spread consternation, but to the myriads that 

 swarm in our meadows and pastures every summer and autumn. 



Although the injuries caused by our common locusts are very 

 great every year, they are more noticeable in seasons of drought. 

 It frequently happens at such times that every blade of grass is con- 

 sumed in extensive pastures. This results not merely from the 

 less luxuriant growth of the grass, but from the fact also that dry 

 weather is favorable to the development of these insects. 



It follows from the above that such treatment of meadows and 

 pastures as shall best enable them to withstand droughts will also 

 serve to protect them from the ravages of locusts. Thus the 

 presence in the soil of a considerable amount of vegetable matter, 

 furnished in the form of stable manure or otherwise, which will 

 retain moisture, will have this tendency : or clover may be used ; 

 this will shade the soil, and will bring moisture and fertility from 

 great depths by means of its long roots. In case of heavy clay 

 lands, tile-draining has been recommended ; this prevents the pud- 

 dling and subsequent baking and cracking of the soil resulting from 

 surface drainage. 



TABLE OF SUB-FAMILIES OF ACRIDID^E. 



A. Pulvilli present between the claws of the tarsi ; pronotum never extending 

 over the abdomen. 

 B. Prosternum unarmed. 



C. Vertex and front of head meeting at an acute angle; vertex extending 

 horizontally ; front strongly receding. (Fig. 92.) I. TRYXALIN^:. 



