How to prevent drywood termites?

I live in Southern California. House is single story.

I recently had some infestations of drywood termites in my attic. We spotted them because they excreted these small tell-tale cylindrical pellets. The house had to be tented at considerable expense.

I noticed that the soffit vents have a quarter inch screen mesh. Would this type of screen allow any swarming dry wood termites to enter the attic?

Would it help to overlay the 1/4" screen with small mesh regular window-screening to avoid future invasions?

Is there anything else I could do to prevent future infestations of drywood termites?

Thanks

Walter The Happy Iconoclast