This is somewhat orthogonal to your point, but my cats are also perfectly capable of eating through a plastic bag enclosing dry foodstuffs (left a sealed bag of

This is somewhat orthogonal to your point, but my cats are also perfectly capable of eating through a plastic bag enclosing dry foodstuffs (left a sealed bag of cat treats on the counter one day, found it chewed through and empty the next). It does seem likely to me, however, that the number of insect species capable of eating through plastics and also breaking the plastic molecules down must surely number greater than one.