Boyd’s Bible Dictionary:
(cancer-worm). A variety of caterpillar. But in Joel 1:4; 2:25; Nahum 3:15-16, probably an undeveloped locust.
Concise Bible Dictionary:
This is supposed to be the “hedge-chafer,” a species of locust. It “spoileth [or spreadeth itself out] and fleeth away.” It devours much herbage, and is used as a figure of the enemies that would destroy Nineveh (Nah. 3:15-16; Joel 1:4; Joel 2:25). The same Hebrew word is translated Caterpillar in Psalm 105:34 and Jeremiah 51:14, 27.
Strong’s Dictionary of Hebrew Words:
Meaning:
from an unused root meaning to lick up; a devourer; specifically, the young locust
KJV Usage:
cankerworm, caterpillar