112 The Rocky Mountain Locust. 



they generally did good by keeping this weed down and 

 converting it into manure. In some few instances, how- 

 ever, they swarmed to such an extent as to devour all the 

 purslane, when they attacked grape-vines, and as Mr. Thos. 

 Wells, of Manhattan, Kansas, informs me, even cut off 

 corn when it was about a foot high. These worms were 

 the variable larvae of the White-lined Morning Sphinx, a 

 pretty moth often seen hovering over flowers at evening. 

 Most insects that naturally feed in spring above ground on 



[ Fig. 19.] 



White-lined Moening Sphinx, 



low vegetation were killed out, and the only species 

 unaffected by the visitation were those feeding on forest 

 trees, or living in the ground or in the trunks of trees. 

 The White-lined Morning Sphinx, was just issuing from 

 the pupa, which had remained undisturbed below ground, 

 when the locusts were leaving. It found the Purslane — its 

 favorite food-plant — everywhere springing up and abun- 

 dant, and its eggs were laid without difficulty, and the 

 young larvae did not, in any case, lack for food. As a 

 consequence they prevailed to a remarkable degree. 



