The Japanese word for ant is
蟻

あり - ari

Japanese Definition

ant
1. 名詞. 蟻。

蟻
1. affix. ant
2. affix. Usage: This reading is only found in compounds. When the character is used on its own, it is always read as the kun'yomi of ari.
3. n. ant
4. n. (obsolete) an ant, particularly one without wings
5. n. (obsolete) an ant egg or larva
6. n. Usage: The spelling of 蟻 for ari no ko is generally only seen in old texts. In modern Japanese, this term is much more commonly spelled as 蟻の子.