I notice many of the Druids good buff spells for their companion target Animals. If a Druid goes with a Vermin companion ala U.M., is there an effective way (w/o using 3pp material) to get those spells to land on their faithful insectoid follower?
If this isn't a PFS game, you should just ask your DM. Most people imply that the wording is meant for all companions, including vermin and the plant companions of Treesinger.
By RAW, there's not a way that I'm aware of. Although, I'd recommend Vermin Heart for a vermin druid, and the Desert Druid allows you to use vermin shape instead of plant shape.
Sorry I don't know more.