Frass refers loosely to the more or less solid excreta of insects, and to certain other related matter.
Bedstraw hawk-moth caterpillar leaving the frass behind
Typical sculpting of a frass pellet of a large caterpillar
A thistle tortoise beetle larva carrying a mass of its own frass as a repugnatorial defence.
Galleries of various species of wood-boring beetles typically are stuffed with frass
Feces are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relatively small amount of metabolic waste products such as bacterially altered bilirubin, and dead epithelial cells from the lining of the gut.
A pet waste station in Tucker, Georgia, US
Cyclosia papilionaris consuming bird droppings
Horse feces
Sign ordering owners to clean up after pets, Houston, Texas, 2011