[2:10] 1 sn Witnesses of locust invasions have described the visual effect of large numbers of these creatures crawling over one another on the ground. At such times the ground is said to appear to be in motion, creating a dizzying effect on some observers. The reference in v. 10 to the darkening of the sun and moon probably has to do with the obscuring of visibility due to large numbers of locusts swarming in the sky.