Insect frass is a very interesting product. Frass is to insects what castings are to worms- it is the waste product left over from the consumption of vegetable matter by insect populations. The term ‘frass’ has German roots, and means ‘devouring like a beast’, which points to the ravenous devouring of vast amounts of plant material, resulting in a type of well rounded compost produced by herbivore digesting insects.