In insects, cellulose digestion is accomplished by three types of enzymes: endo-cellulases, exo-cellulases, and cellobiases. Many insects synthesize their indigenous exo-cellulases and cellobiases, but few can synthesize endo-cellulases. Several insect cellulases have been purified and characterized. A diverse assemblage of protozoan, fungal, and bacterial species living in the guts of insects produces cellulases. In nature, some plants can protect themselves against pests by synthesizing the specific macromolecules in form of cellulase inhibitors. Tribolium castaneum belongs to Coleoptera is economically important species of beetle attacks stored grain products such as flour, cereals, meal, crackers, beans, spices, pasta, cake mix, dried pet food, dried flowers, chocolate, nuts, seeds, and even dried museum specimens. It uses its cellulase and amylases for digestion of food material and use it as energy source. The Study of T. castaneum cellulolytic system can provide us better understanding about how these pests cause huge loses and can help us in developing better pesticides which can effect the eating habits of these pests.