If the leafy growth has turned brown/yellow, that means the bulbs are dormant and yes, that's the time to divide them.

Hi, welcome to GoY, do you know which of the 26 species of Arum you have ?, most flower in spring, and should be divided after flowering, you can sow seed in autumn, in containers in a cold frame, but remove the outer pulp first, as it can be caustic I would suggest you wear rubber gloves to do this, Derek.

I inadvertently move them when i'm digging around them at any time of the year. the corms seem very resilient. even when I am trying to dig them out to get rid they seem to come back.