A primary consumer consumes the plant. Thus, insects are primary consumers since lots of insects feed on plant material. Frog is an example of secondary consumers since it feeds on insects and hence it should come after insect in the given food chain. Wolf and snakes are tertiary consumers. The secondary consumers are eaten by tertiary consumers. Thus, in the given food chain, the frog will eat insect and in turn, the frog will be eaten by the snake. Ichthyophis is a limbless amphibian which looks like a snake. Some species of Ichthyophis can feed on small snakes.