Changing Pizzicato to Arco

I am writing a song containing Violins, Violas, and Cellos. The first half of it is entirely in Pizzicato while the second half changes to Arco. At the moment, I have two of each instrument to accommodate for this change, but I'm wondering if you can change a single instrument from Pizzicato to Arco within the song.

Or, if that's not possible, I've also seen numerous compositions where an instrument will disappear from the score at a measure where it is no longer used. How can I do that?