Why they are Beneficial
The adults are active predators of insects, catching and grasping them with their front legs.
The larvae of one subfamily Mantispinae, are exclusive parasitoids of spider eggs. They will hop onto a passing female spider entering the egg sac if the spider already has one, or wait until one is produced. The larva will feed on the eggs using their modified piercing and sucking mouthparts.
These larvae look like brown lacewing larvae at first but once they enter the spider sac they become grub like. The larva will pupate inside the egg sac and emerge as an adult. Different species will be host specific to a particular species of spider.
The larvae of the subfamily Symphrasinae, are parasitoids of bees, wasps or beetles; Calomantispinae and Drepanicinae most likely predate on the larvae of bees, beetles, wasps and other arthropods, although very little is known about these.
