Neuropteroids
Within the Neuropterida, adults have chewing mouthparts, but the mandibles of male dobsonflies are non-functional in feeding. The larvae in many lineages are predatory, with mandibles modified with grooves along which digestive saliva flows, while the larvae of the family Sisyridae have the mouthparts developed into a sucking tube which they use to feed on the liquid tissues of freshwater sponges.
Read more about this topic: Mandible (insect Mouthpart)