Injury from the Young. 



Ill 



Springing up wherever the blue grass gets killed out, it 

 proves a godsend to the people, for while it is young and 

 tender, cattle like it and fatten upon it. This grass is the 

 Vilfa vaginceflora, an annual which is common from the At- 

 lantic to the Rocky Mountains. Unnoticed during ordinary 

 seasons, the destruction of the blue grass and other plants 

 by the too close gnawing of the locusts, gives it the advan- 

 tage in the struggle for existence — an advantage which is 

 soon lost, however, as the normal relations between species 



[Fig. 18.] 



Black Lakva of White-liked Morning Sphinx 



are assumed again in a few years after the disturbing 

 influence has ceased to be operative. Indeed, since the 

 Vilfa ripens and dies early in the fall, the blue grass gains 

 ground the very first year, and afterward easily retains 

 supremacy. The wide-spread appearance of the Vilfa, 

 following the locusts, has been explained on the hypothesis 

 that the latter brought the seed from the West and passed 

 it undigested with their droppings. The fact that the seed 

 is a line long, and not particularly hard, aside from the 

 other facts in the case, renders such a hypothesis unreason- 

 able. Being an annual, the seed was scattered the previous 

 fall, and naturally starting, we may presume, about the time 

 the insects left, the species got the ascendency. 



Some persons were quite alarmed at the prevalence of 

 large green and black worms, soon after the locusts left. 

 Feeding upon purslane and prevailing to an unusual 

 degree, because of the unusual prevalance of this plant, 



