Mantis

Not the best idea, most of the pests that affect cannabis are numerous and small. Fungus gnats, spider mites, aphids and thrips. These are all better handled by smaller predators. Mantis eat larger things that are both pest and predator. If it cant fit nicely between their raptoral forlegs/forearms its not up their alley. You'd have better luck with predatory mites or nematodes or BTi. Indoor is easier to manage then outdoor. If this is outdoor, can only plant things like dill and marigolds to bring in other predators like tachinid flies, hoverflies, ladybugs and parasitic wasps. They love cluster flowers like dill and cilantro. Look into bait crops if you have issues with some bugs and companion planting for attracting the beneficials. Good Luck!