They only found polystrene worked. Cockroaches could digest it as well but some of the toxic components made it through their digestion system. The difference with mealworms was they were able to completely digest the plastic rendering it into benign organic matter. Check over the whole presentation and you'll find the original science article on mealworms eating plastic.

Motherjones just ran an article on feeding insects to farm animals. I've been preaching this for years. Raising mealworms using polystrene for food could remove thousands of tons of plastic waste from the waste stream and turn it into food for people, eggs, chicken, fish and pork. That seems like a better solution than attaching caps to drink bottles, better known as sports bottles. So frustrating such lame ideas made it to round two.

http://www.motherjones.com/environment/2017/08/feed-flies-factory-farm-livestock-fish/

Think in terms of pounds or better yet tons of caps to have an actual value. How is this currency? Who pays the value beyond the price of the plastic and trust me plastic isn;t worth much! It's why I suggested a lottery system but that idea didn;t make it past the first round. 18 pages of concept and some one suggesting calling caps currency beats it out. I feel so stupid right now for wasting my time on this one! Actual proposals apparently didn't stand a chance. I was told

"Ultimately, your submission was not in-scope for this particular Challenge"

and yet this was in scope? Why not say caps are worth $10 each? I'm sure most would get turned in but who pays the cost? I suggested million dollar lotteries but the costs would be spread over hundreds if not thousands of companies advertising budgets. At least that proposal explained the value and how it was to be paid for. What did they just pull the first round winners out of a hat?