What is "rocky mountain locust"

Rocky \Rock"y\, a.

1. Full of, or abounding in, rocks; consisting of rocks; as, a rocky mountain; a rocky shore.

2. Like a rock; as, the rocky orb of a shield.
   --Milton.

3. Fig.: Not easily impressed or affected; hard; unfeeling; obdurate; as, a rocky bosom.
   --Shak.

   Rocky Mountain locust (Zo["o]l.), the Western locust, or grasshopper. See Grasshopper.

   Rocky Mountain sheep. (Zo["o]l.) See Bighorn.

The Rocky Mountain locust (Melanoplus spretus) is an extinct species of locust that ranged through the western half of the United States and some western portions of Canada until the end of the 19th century. Sightings often placed their swarms in numbers far larger than any other locust species, with one famed sighting in 1875 estimated at in size (greater than the area of California), weighing 27.5 million tons, and consisting of some 12.5 trillion insects – the greatest concentration of animals ever speculatively guessed, according to Guinness World Records.

Less than 30 years later, the species was apparently extinct. The last recorded sighting of a live specimen was in 1902 in southern Canada. Because a creature so ubiquitous was not expected to become extinct, very few samples were ever collected (though a few preserved remains have been found in Grasshopper Glacier, Montana). North America is the only continent without a major locust species, apart from Antarctica.