Transcript:

Today on Animal Fact Files we’re talking about parasitic wasps. Thank you to eliariellis elisalovesart for today’s request! A parasitic wasp is a wasp that spends at least part of its life cycle on or inside the body of a host species. They aren’t true parasites because at the end of the process their host dies. They also aren’t predators because they don’t immediately kill their host. With parasites like tapeworms, the point is to keep the host alive because the parasite depends on the host’s survival to live. This is true for parasitic wasps until a certain point, when they finish off their host and move on with their life cycle. This is why they’re called parasitoids - and there are thousands of them.

Many people hear the word wasp and think of the larger social wasps that pose a threat in the form of a sting, but most parasitic wasps either can’t or don’t sting humans, and, to the human eye, would look more like gnats than wasps. Most species are less than half an inch (15.24 centimeters) long. And often the eggs, larvae, and pupae are unseen, hidden within their host. There are, however, some species of parasitic wasps who appear larger than most such as the cicada killers we’ve discussed in a previous episode.

Parasitic wasps are considered cosmopolitan. They live where their hosts live. Leaf litter, fallen trees, stream sides, agricultural fields, and patio gardens may all house parasitic wasps. Since most parasitic wasp hosts are other arthropods, places where these animals tend to flourish also bring in droves of parasitic wasps. The “host” in this relationship is the animal that is used a nourishment, and sometimes protection, for the parasitoid wasp. For example, we’ve talked about hummingbird hawk moths previously; their larvae, or caterpillars, are often host to parasitic wasps. In the case of this relationship, it’s easy to see the somewhat gruesome development of wasp pupae taking place. That’s because, in this case, the wasps are ectoparasites to the caterpillar. In other cases the wasps may be endoparasites, living inside their host until they chew their way through the host’s body and emerge as adults. It might even seem cruel, but it’s nature, and, in fact, it’s beneficial to humans as many of the hosts parasitic wasps utilize are pest species to our crops.

The life cycle of parasitic wasps can differ vastly between species. Typically a female will emerge from a pupa or host, seek out a mate, and then lay her eggs on or in a new host. But some species don’t have males at all, others go through this cycle multiple times on the same host - thus producing multiple generations in the host’s single generation, and others have even had to learn to dive underwater in order to lay their eggs in aquatic host species. Then there are species who control their host, such as the wasp that makes its spider host spin a cocoon for the invader before being consumed from the inside out. There are also species that specifically target host eggs, like ensign wasps who deposit their eggs in the ootheca of cockroaches - and that’s just barely scratching the surface of parasitic wasp life cycle diversity!

For the most part, parasitic wasps eat the host from which they emerge, but some adult forms may also take food in the form of pollen, nectar, honeydew, and even other, non-host arthropods. In turn, parasitic wasps may be taken by other arthropods such as spiders, as well as arthropod eating animals like reptiles, amphibians, and birds. How long they can live depends largely on the species, but an average parasitic wasp lifespan is likely less than a year.

For more facts on parasitic wasps, check out the links in the description. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files.