Wow! Thanks for that. My son said they were 白蟻 "shiro-ari" which simply translates as "white ant" in English, but according to the Japanese Ant Guide, the pheidole noda is called "ōzu-ari" which I think would be 大相蟻, meaning "grand ant".
But mine certainly weren't as big as the guide suggests, so I'm guessing they are still growing - due to it still being a bit chilly. I know where the nests is, so I'll try for some more shots later in the spring and summer.

