Parasitoid wasp
Parasitoid wasp species differ in which host life-stage they attack: eggs, larvae, pupae, or adults.
Some endoparasitic wasps of the superfamily Ichneumonoidea have a mutualistic relationship with polydnaviruses, the viruses suppressing the host's immune defenses.
[1] Parasitoidism evolved only once in the Hymenoptera, during the Permian, leading to a single clade called Euhymenoptera,[2] but the parasitic lifestyle has secondarily been lost several times including among the ants, bees, and vespid wasps.
Host insects have evolved a range of defences against parasitoid wasps, including hiding, wriggling, and camouflage markings.
Most females have a long, sharp ovipositor at the tip of the abdomen, sometimes lacking venom glands, and almost never modified into a sting.
Most ectoparasitoid wasps are idiobiont, as the host could damage or dislodge the external parasitoid if allowed to move or moult.
Most endoparasitoid wasps are koinobionts, giving them the advantage of a host that continues to grow larger and remains able to avoid predators.
If a polydnavirus is included, it infects the nuclei of host hemocytes and other cells, causing symptoms that benefit the parasite.
Endoparasitoid eggs can absorb fluids from the host body and grow several times in size from when they were first laid before hatching.
They may also get rid of their frass (body wastes) and avoid plants that they have chewed on as both can signal their presence to parasitoids hunting for hosts.
Ants that are in a symbiotic relationship with caterpillars, aphids or scale insects may protect them from attack by wasps.
[25] D. melanogaster females lay their eggs in food containing toxic amounts of alcohol if they detect parasitoid wasps nearby.
[26] Based on genetic and fossil analysis, parasitoidism has evolved only once in the Hymenoptera, during the Permian, leading to a single clade.
[30][31] The common ancestor in which parasitoidism evolved lived approximately 247 million years ago and was previously believed to be an ectoparasitoid wood wasp that fed on wood-boring beetle larvae.
[30] A significant radiation of species in the Hymenoptera occurred shortly after the evolution of parasitoidy in the order and is thought to have been a result of it.
[35] Symphyta: Apocrita: Parasitoid wasps are considered beneficial as they naturally control the population of many pest insects.
[b] In an 1860 letter to the American naturalist Asa Gray, Darwin wrote: "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.
"[3] The palaeontologist 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.
