Bipalium is a genus of large predatory land flatworms, terrestrial planarians. They are often loosely called "hammerhead worms" or "broadhead planarians" because of the distinctive shape of their head region. Land planarians are unique in that they possess a "creeping sole" on their ventral side. Several species are considered as invasive to the United States. Bipalium species are predatory. Some species prey on earthworms, while others feed on mollusks. It has been shown that the flatworms can track their prey. When captured, earthworms will begin to react to the attack, but a flatworm uses the muscles in its body as well as sticky secretions to attach itself to the earthworm to prevent escape. Several studies have indicated that the planarians will cover, or cap the prostomium, peristomium and anterior end to end the violent reaction by the earthworm To feed on its prey, a flatworm extends its pharynx out from its mouth on the mid-ventral portion of its body and secretes enzymes that begin digestion of the earthworm external to the flatworm. The liquefied earthworm tissues are sucked into the branching gut of the flatworm by ciliary action.