Why Wasp attacks spiders

Wasps in the family Pompilidae are commonly called spider wasps or pompilid wasps. The family is cosmopolitan, with some 5,000 species in six subfamilies. All species are solitary, and most capture and paralyze prey, though members of the subfamily Ceropalinae are cleptoparasites of other pompilids, or ectoparasitoids of living spiders.

In South America, species may be referred to colloquially as marabunta or marimbondo, though these names can be generally applied to any very large stinging wasps. Furthermore, in some parts of Venezuela and Colombia, it is called matacaballos, or “horse killers”, while in Brazil some particular bigger and brighter species of the general marimbondo kind might be called fecha-goela, or “throat locker”.

Unlike many other families in the order Hymenoptera, wasps in this family are solitary and nest alone. A female wasp will search the ground and tree trunks for a spider, and upon finding one, will sting it, paralyzing the spider. Once the spider is paralyzed, the female wasp will make a burrow or take the spider to a previously made burrow. She will lay one single egg on the abdomen of the spider using her ovipositor, and then enclose the spider in the burrow. The egg will hatch and the larva will feed on the spider, breaking through the integument with its mandibles. The larva has five instar stages before it pupates; no major morphological differences are noted between the first four instars, with the exception of size. At the conclusion of the final instar, the larva will spin a silky cocoon, where it will emerge as an adult either later in the same summer season or will overwinter, depending on the species and the time of year the larva pupates.

Adult Pompilidae are nectar-feeding insects and feed on a variety of plants. The female wasps search for a variety of spiders for their larva to feed on, including wolf spiders (Lycosidae), huntsman spiders (Sparassidae), and baboon spiders (Harpactirinae). As the larva feeds on its host, it saves the vital organs, such as the heart and central nervous system, for last. By waiting until the final larval instar, it ensures the spider will not decompose before the larva has fully developed.

Brazilian wanderer spider vs tarantula hawk wasp.

This Video shows a battle between a Spider and Wasp