This guy was a little easier to spot on our largest broccoli start because there were very obvious holes in the leaves. With the imported cabbage worm, it seemed like they ate the leaves fairly indiscriminately, leaving only the veins behind. The cross-stripped cabbage worm, though, chews circles in the leaves that make it fairly obvious that something is going on.
I only found one, but will have to keep a watchful eye out. Where there’s one, there’s likely more.