In the first study researchers found that mealworms fed only Styrofoam were just as healthy as mealworms fed the more traditional meal (bran, in this case). Each worm could eat about a pill-sized portion every day.
In the second study focused on the mealworms’ gut microbes, which are able to break down the plastic safely. The researchers were able to turn this bacteria into a film that they applied to polystyrene, a form of the same plastic used to make Styrofoam. The bacteria were also able to eat through polystyrene, but at a much slower rate than the mealworms.
http://www.popsci.com.au/science/nature/mealworms-can-happily-and-safely-eat-styrofoam,409996