(Hebrews yelek), "the licking locust," which licks up the grass of the field; probably the locust at a certain stage of its growth, just as it emerges from the caterpillar state (Joel 1:4; 2:25). The word is rendered "caterpillar" in Psalm 105:34; Jeremiah 51:14, 17 (but R.V. "canker-worm"). "It spoileth and fleeth away" (Nahum 3:16), or as some read the passage, "The cankerworm putteth off [i.e., the envelope of its wings], and fleeth away."

Noah Webster's New International Dictionary of the English Language

(n.) The larva of two species of geometrid moths which are very injurious to fruit and shade trees by eating, and often entirely destroying, the foliage. Other similar larvae are also called cankerworms.