Final answer:
Predatory insects and spiders inject venom into their prey when they bite. This venom can paralyze or kill the prey, which is a critical aspect of these predators' ecological niche. While the venom from most of these creatures is not harmful to humans, some species can pose a threat.
Step-by-step explanation:
When predatory insects and spiders bite their prey, they often inject venom to incapacitate or kill them. Spiders across the globe use venom, particularly notable in species like the black widow spider, which injects a potent concoction including latrotoxins that can cause significant symptoms in humans, though usually only female bites are dangerous. Similarly, other arachnids such as scorpions possess a specialized venom-injecting barb at the end of their tail, with venom glands that release fast-acting venom to paralyze or kill their prey. Most of these creatures are not harmful to humans, and only a few species pose any real threat. Moreover, some predatory insects have specialized mouthparts or stingers to inject venom into their victims, often featuring as part of their ecological niche.