In this paper, a scanning electron microscope (SEM) is used for microstructural investigations of a woodlouse shell. Finite element (FE) method is employed to study the dynamic behavior of the shell subjected to the impact of a cone-shaped projectile. Despite of small thickness, the shell, as a composite material, enables the insect to bear large external forces. The woodlouse is also able to roll up into a complete sphere to protect itself from danger. In order to study this defense mechanism, the external loads are applied to the shell in different configurations: when the shell is in (1) normal and (2) rolled-up forms. The simulations are performed at different velocities and at different impact angles. Comparisons of the results obtained from different simulations indicate that the defense mechanism of the woodlouse has an important role in decreasing the stress concentrations. Indeed, it is a defense mechanism which effectively increases the load-bearing capacity of the insect shell. The results of the present research may be useful in the design and manufacture of modern engineering structures with a high strength to weight ratio.