What kind of energy transformation is taking place in the caterpillar's body while the caterpillar eats the leaf in the photograph?

The energy transformation that is taking place in the caterpillar's body while the caterpillar eats the leaf would be first it would be Chemical Energy, that would be from the leaf the caterpillar is eating then when the energy is used it would transform to mechanical thus it is a chemical to mechanical energy.

for Apex its

Solar energy - > Chemical energy