I noticed you live in Zone 4 which suggests cooler than usual temperatures. However, I also read that you have had "great success" in earlier years with Drosera regia. Since you are a savvy grower, I don't see that you need to take any extra special steps such as styrofoam containers to protect your flytrap. A styrofoam pot would only insulate the roots and not the vegetative top, anyway. A drawback to styrofoam is its lack of durabiity and, for some, its unsightlyness.

Thank you for your reply. And you are correct about the cooler temps, at least during the fall and winter (though summers can reach in the very high 90's here and with higher humidity). I think I'll go with plastic for the planter.

They work fine. I lot of people grow stuff in those 20 oz. styrofoam cups. My VFTs are in them. Use WHITE ones, they reflect the Sun/heat.

I don't know, I'm kind of thinking about using plastic now, if it has better aesthetics and durability. I just heard from an online site that since foam can better insulate the roots, it can prevent them from overheating or getting too cold. I will be using pretty decent air circulation and monitoring temps and humidity, so I'm not sure how much of an issue soil temperature will be, though I have seen some sites where people were using foam coolers as large planters.

To me, a large styrofoam drink cup makes a very unbecoming plant container especially if it is advertising something. Also, nothing grows to its best potential in a drink cup; plants need better/more root-run space that provides a more stable root environment.

To me, using a styrofoam cup for a planter is downright ugly, but worse, a small container like this does not allow the plant to reach its full growth potential. Plants need more root room than a drink cup provides. A larger container/pot will simply provide a much more favorable overall environment for the plant.