The spines on this caterpillar provided no protection against the minute parasitic wasp that laid her eggs on or inserted them into the caterpillar’s body. Upon hatching, the larvae consume the tissues of the host, largely avoiding vital organs, so that the caterpillar can continue to eat and grow sufficiently to nourish the developing wasps through their development.
The larvae reached full size, emerged through the skin of the caterpillar, and formed cocoons (the white structures above) on the outside of the caterpillar. Several days later a small adult wasp will emerge from each cocoon by breaking it open at a preformed line of weakness, appearing as a cap at the top of each cocoon.
Although the caterpillar was still alive yesterday, when this image was taken, the caterpillar lacks sufficient remaining tissue to pupate and continue its own development.