Describe in detail how are crayfish hunts and eats its food.

Crayfish use their large pincers to capture common prey items, such as worms, leaches, snails. Additionally, crayfish occasionally capture large prey, such as frogs, fish, salamanders and tadpoles. Frog eggs and insects are important foods for the juveniles of many species.

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.