Glyptapanteles

Glyptapanteles is a genus of endoparasitoid wasp found in Central and North America. The larvae of the members of "Glyptapanteles" manipulate their hosts into serving as bodyguards.
Reproduction.
Female "Glyptapanteles" stick their ovipositor into caterpillar hosts. The eggs hatch inside the caterpillar. The caterpillar feeds and grows normally until the 4th or 5th instar. Then up to 80 fully grown larvae emerge from its body to pupate.
Behaviour changes.
After the larvae of "Glyptapanteles" emerge, the caterpillar takes up position near the cocoons of the pupae, arches its back, and ceases to move or feed. It will occasionally spin silk over the pupae. However, when disturbed, it begins to thrash violently. This behavior is to strike at and repel possible predators of the pupae, so improving the survival odds of the wasp pupae. Only about one in twenty non-parasitized caterpillars responded in this fashion. In 60% of cases, the parasitized caterpillars successfully warded off these potential predators. No longer eating, the affected caterpillar eventually dies.
Mortality rates for pupae not guarded by parasitized caterpillars were significantly higher.
Mechanism.
In the course of Grosman's research, it was discovered that not all larval "Glyptapanteles" emerge from their caterpillar host. One or two remain behind and active. Probably these larvae manipulate the host. It is a kind of altruism, since these larvae miss their own chance of pupating in order to protect the brood.