What do you call a insect eating another insect?

the mantis, centipedes, scorpions, Spiders, dragonfly, lady byrd

centipedes, scorpions, and spiders are NOT insects...

-but scropionflies are predatory (Mecoptera: Panorpidae), so are lacewings, lady beetles (lady bird beetles is a European common name for lady beetles), also syrphid flies in the immature life stages, certain cecidomyiid flies, antlions, etc. There are also parasitoids, in which in the immature must utilize a host to complete their life cycle, but unlike predators, they only kill one host within their lifetime.