Spider wasps are conspicuous and usually have warning colorations (usually combination of black and yellow, orange, or red) that help “educated” would-be predators of their ability to sting. Apparently, in some species, even the males (which do not possess stingers) have a disagreeable smell or taste. Once a flycatcher (for example) is stung by a black-and-orange spider wasp, it knows to avoid similar-looking insects. Many other insects that are perfectly edible and harmless gain protection from predators by having the same coloration, body shape, and even flying style of spider wasps. Mydas flies are an example of these mimics.
Spider wasps are called parasitoids because their larvae, like parasites, take nourishment from a living host — but unlike typical parasites, they ultimately kill their hosts (hence the word’s “-oid” ending). Other parasitoid animals include tachinid flies, some types of ground beetles, and ichneumon and braconid wasps. (Braconids are the insects that are famous for eating a hornworm’s body juices from the inside, then pupating in small silken cocoons on the caterpillar’s outer skin.)
In some cases, if a spider stung by a spider wasp manages to escape being buried with an egg on it, the spider can eventually recover and survive its brush with doom. Numerous studies have been made of the stinging behavior of various spider wasps; some use a few quick stings to initially subdue a spider, then administer another sting, slowly, into the underside of the front of the body, where the nervous system is most concentrated. After that, the spider is probably a goner.
Tarantula hawk wasps (Pepsis and Hemipepsis spp.) are in this family, and they are famous for their large size, long stingers, and excruciating stings (should anyone dream of handling them). They specialize in capturing tarantulas, so these wasps are most numerous and diverse in the desert southwest, where tarantulas are abundant. If you go to the desert southwest, keep an eye out for these huge insects! (Or, look for videos of their battles online.)
One species of tarantula hawk is found throughout the eastern United States: the elegant tarantula hawk (P. menechma). It feeds, however, mostly on trapdoor spiders, not tarantulas. It is glossy blue-black with bright yellow antennae. Also, the southwestern species P. pallidolimbata has been found in southwestern Kansas and central Nebraska, so it’s not unreasonable to think that it might eventually be seen in southwest Missouri — the part of our state where tarantulas are most abundant.