Melanoplus sp..
Photo: 05/15/16, 6 pm.

Possibly a nymph of Melanoplus punctulatus. The genus has 239 species in North America. An infamous (now extinct) representative is the Rocky Mountain locust which caused significant pests in the 19th century Great Plains. Follow the second link to a vivid report about these swarms that apparently reached sizes of 12.5 trillion insects. 

bug guide (these photos):
history net - 1874: