Tsetse fly
Normally, insect larvae feed themselves before pupation, but tsetse development (before it emerges as a full adult) occurs without feeding. The development is based only on nutritional resources provided by the female parent, which shows how blood is a rich source of nutrition. The female must get enough energy for her needs, for the needs of her developing offspring, and to store the resources which her offspring will require until it emerges as an adult.