The American Pelecinid Wasp – Parasite or Protector?

Josh Brog and Connor Mikulski

Wasps are often unfairly perceived as ferocious, bloodthirsty, and insatiable predators. Among these alleged perpetrators is the American Pelecinid Wasp (Pelecinus polyturator) pronounced (pel-e-SY-nid). Now you have nothing to fear unless you happen to be a beetle larva, which of course, you are not! These wasps are nothing to be afraid of as they have no interest in you and grow to a mere 2.5 inches, roughly the size of maybe one and a half to two paper clips!

“Pelecinus polyturator ♀” by Wedontneedfeatherstofly is licensed under CC BY 2.0

Wasps are often unfairly perceived as ferocious, bloodthirsty, and insatiable predators. Among these alleged perpetrators is the American Pelecinid Wasp (Pelecinus polyturator) pronounced (pel-e-SY-nid). Now you have nothing to fear unless you happen to be a beetle larva, which of course, you are not! These wasps are nothing to be afraid of as they have no interest in you and grow to a mere 2.5 inches, roughly the size of maybe one and a half to two paper clips!.

At first glance, the insect looks capable of inflicting harm on any animal imaginable. But despite its menacing appearance, the American Pelecinid Wasp could not be any more harmless to humans or their pets (unless, of course, you have a pet June beetle sp.)! June beetles are the main source of food for wasp babies and are a regular pest to plant life, and the grubs (beetle larvae) can cause quite a bit of damage to garden plants. These little grubs can cause mass destruction by feeding on the roots of your flowering plants, leaving them for dead, or at least much less pretty than when you first planted them. Adult pelecinid wasps have a very mellow diet that includes feeding on the nectar of flowers in both gardens and woods. Like all other ants, bees, and wasps, they have absolutely no interest in tasting human blood! In fact, this wasp doesn’t even have a stinger on the end of its extremely long abdomen that happens to be 5x the length of their body! Rather, females use this body part to lay their eggs on the backs of grubs that live underground and occasionally use it to poke and prod and intimidate other insects.

While we humans have nothing to fear, June beetle grubs should be afraid of this wasp. Very afraid. The American Pelecinid Wasp is a “parasitoid” which means its larvae act as a parasite and use the host as a food source and eventually kill it. Kind of like the movie, “Alien.”As mentioned above, mother pelecinid wasps deposit their eggs on the backs of June beetle grubs, which later hatch and burrow their way into the grub as they eat it from the inside out! For most parasitoid wasps, at the larval stage, they prolong the parasitic stage. The larvae keep the host alive by eating around the vital organs, and since the grubs are still alive, this keeps everything fresh like your refrigerator. If the wasp larvae ate everything and killed the grub too quickly, they would have to eat rotten food until they were mature enough to emerge out of the grub and how gross would that be! But the American Pelecinid Wasp kills its host rather quickly because it doesn’t mind eating the dead tissues. These grubs also provide all the protein the wasp needs for its whole life! After the wasp eats the grub, the American Pelecinid Wasp larva pupates right there in the ground, and when it emerges as an adult, it will only need to sip nectar for energy!    

To add to their already impressive resume, female American Pelecinid Wasps can lay eggs that develop into female wasps without the help of a boyfriend! With almost all of the other ants, bees, and wasps, unfertilized eggs would hatch into males because they are haploid individuals (only need one set of chromosomes). However, to have daughters, most wasps need to find a partner because females are diploid, meaning they have two sets of chromosomes, one from mom and one from dad. But perhaps the weirdest thing about the American Pelecinid Wasp is that they can have daughters without mating.  In other words, they can produce diploid eggs without any fertilization, through a process called parthenogenesis. This strange combination of celibacy and becoming mothers to girl wasps seems to vary from place to place.  Nobody knows why, but it probably doesn’t depend on local traditions and social norms.

  The next time you come across one of these impressive specimens, instead of running away out of fear of its unique appearance, be sure to watch closely and admire.  For all of its spectacular feats, this magnificent insect has undoubtedly earned its place in the wild!