Is there another way to sign "ant"?
Yes! Many fluent signers simply fingerspell A-N-T. Alternatively, they might use the general sign for "bug" (placing the thumb on the nose and wiggling the index and middle fingers) if the context already makes it clear.
Can I use this sign for other insects?
Yes, this crawling hand motion acts as a classifier that can represent various crawling bugs or spiders. You can fingerspell the specific insect's name first, then use this motion to show it moving.
How do I show a whole colony of ants?
To show a swarm or colony, use both hands in a curved, open "5" handshape (claw hands) facing down. Wiggle all your fingers while moving your hands around to represent many ants moving together.