Parasitoid wasps are a little known, but extremely prolific group of wasps, who provide one of the best examples of evidence for evolution that I’ve come across. Parasitoid wasps have a particularly gruesome way of life. They make a living by laying their eggs inside the larvae of another insect, often a caterpillar. As the young wasp develops, it devours the host from the inside out, eventually emerging and killing the host.
Parasitoid wasps are found in 37 different families of a single order, the Hymenoptera, which contains all bees, wasps and ants. There are thousands, maybe even millions of species of parasitoid wasp, each preying on a different host, utilising a different set of tactics to subdue their victim. Many parasitoid wasps are considered to be beneficial to humans because they kill garden pests such as aphids. But this is not the important part of the story.
While parasitoid wasps inflict an unpleasant death on their victims, they are not without something to fear themselves. Because out there, in nature, exists something more horrible – the hyperparasitoid wasp. Hyperparasitoid wasps lay their eggs within the developing larvae of parasitoid wasps – that is, a larva developing within a larva within a larva. And furthermore, there is such a thing as a superparasitoid wasp, whose eggs develop within the larvae of the hyperparasitoid. That these wasps are able to locate an appropriate host; a caterpillar with a parasitic larvae that has itself been parasitised by another wasp, is truly remarkable.
Parasitoid wasps and their higher-order parasites, are among the strangest and most unpleasant feats of evolution. They are extremely successful and our understanding of their biology is still very limited. They have been known since Darwin’s time though, and Darwin himself saw them as clear evidence against intelligent design and for evolution:
“I cannot persuade myself that a beneficent and omnipotent God would have designedly created Ichneumonidae with the express intention of their feeding within the living bodies of caterpillars”. – Charles Darwin (1896)
Articles in this Series:
- Intro: Reasons Why Evolution is True
- Part One: The Panda’s Thumb
- Part Two: Parasitoid Wasps
- Part Three: Ring Species
- Part Four: Galapagos Finches
- Part Five: The Quirky Human Eye
- Part Six: Homology
- Part Seven: Coevolution
- Part Eight: PreCambrian Rabbits
- Part Nine: DIY Evolution
- Part Ten: Convergent Evolution