Whatever it is. It sounds creepy. Tie the plastic bag tightly, maybe double bag it so those suc***s can't escape.

If you are renting this space the home owner should be responsible for the costs. However you may want to get rid of some of the clutter before the owner sees it.

Personally I happen to be a pack rat. It takes an emergency such as a water heater or pipe breaking before I start to discard things. I found bagging most things and putting in the backyard helps. Once outside of my house what I thought were treasures often are not.

If these items are in plastic bags the critters will die (a safe amount of time might be 1 or 2 weeks) and you can place them back into your basement or possible decide to have a yard sale or donate to Salvation Army. I find I can never throw anything away but I enjoy giving things to others.