Parasite Wasp: The Wasp Family's Scariest Member

Because of their apparent hostility and capacity to sting repeatedly, Wasps have a reputation for being jerks. They're frequently likened to honey production and agricultural pollination by bees in a bad light. Wasps, on the other hand, are downright saintly in comparison to their parasitic brethren.

Parasitoid Wasps

All parasitoid wasps, except wood wasps (Orussoidea), are members of the wasp-waisted Apocrita superfamily. They lay their eggs on or in the bodies of other arthropods as parasitoids, causing their hosts to die sooner or later. Different species prefer different insect orders as hosts, most commonly Lepidoptera, while others prefer beetles, flies, or bugs; spider wasps (Pompilidae) attack only spiders.

Parasitic wasps sting to inject their eggs, often accompanied by venom and a virus, into their hosts. Their larvae develop and finally emerge from the unwary host, killing it. Then they grow up and fly away, continuing the cycle.

A Diverse Species

There are many parasitoid wasp species, but most are so tiny that they go unnoticed. However, they make up for their lack of size with sheer numbers and efficiency, and as a group, they may be the most important biological control strategy available to gardeners.

Parasitoid wasps come in various sizes, from very small (some can fit through the eye of a needle) to about 12 inches long. They do not sting since they are not interested in humans.

Life of a Parasite Wasp

The parasitoid egg hatches into a larva or two or more larvae on or inside the host (polyembryony). Endoparasitoid eggs can absorb fluids from the host's body and expand several times their original size before hatching. The first instar larvae are frequently highly mobile and may have solid mandibles or other features to compete with other parasitoid larvae.

Depending on its species, the parasitoid may subsequently eat its way out of the host or remain in the more or less bare skin. The insect then spins a cocoon and pupates in either circumstance.

Because they naturally eliminate agricultural pests, many parasitoid wasps are considered beneficial to humans. Some are used commercially in biological pest control, such as Encarsia formosa, which was first used to control whitefly in greenhouses in the 1920s. Wasp parasitoidism affected Charles Darwin's ideas in the past.

Charles Darwin on Parasitoid Wasps

Parasitoid wasps impacted Charles Darwin's ideas. For example, Darwin wrote to American naturalist Asa Gray in an 1860 letter:

"I cannot persuade myself that a beneficent and omnipotent God would have designedly created parasitic wasps with the express intention of their feeding within the living bodies of Caterpillars." The paleontologist Donald Prothero notes that religiously-minded people of the Victorian era, including Darwin, were horrified by this instance of evident cruelty in nature, particularly noticeable in the Ichneumonidae.