First the parasitoid eats the fat bodies of the larva, then the digestive organs, keeping the heart and central nervous system intact for as long as possible. Finally, these are consumed as well and the long-suffering victim dies, leaving behind an empty shell.
19th century scientists and theologians struggled with the idea of parasitoid insects and their grizzly lifecycle. The slow death endured by the host was discussed at length by the likes of Charles Darwin as well as others held in high academic esteem during his time. Darwin himself said, in a letter to Asa Gray in 1860, “I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of Caterpillars…”
Giant Ichneumons are the largest parasitic wasp in Missouri. They are found throughout much of the Eastern United States as well as Southern Canada and most of Mexico. These large insects are distant cousins to the much-maligned wasps. While admittedly they look threatening in a very scary way, they are completely harmless to humans. Unlike their wasp relatives they lack a stinger to protect themselves. Instead, the long thread-like extension projecting from the abdomen of the female is called an ovipositor. While it looks like a seriously dangerous stinger, it is completely useless as a defense mechanism. Instead, its only purpose is to lay eggs. Females are the only ones to possess an ovipositor, males lack any projection at all.After mating, a female looks for a tree, or stump in the beginning to advanced stages of decay. They seem to prefer trees about 3 to 4 years into their decaying process, this may be due in large part to how much easier it would be to insert her ovipositor within the wood at that stage of decay. Like all parasitic wasps she is searching for the host insect that her offspring will feed on. Horntails, another relative to the wasp, is the quarry she seeks. Once she has located a suitable candidate, she will then drill her 2- to 4-inch-long syringe-like ovipositor into the wood and paralyze the horntail larvae.