When larvae hatch from their eggs, they are either red or yellow. Their bodies have a slender and flat appearance with short legs due to their minimal movement. The larvae are covered in hair and have two horn-type projections on the dorsal area of the last body segment. Immediately after birth, they start searching for food close to where they hatched. They feed on wood-borer insects on trees, or feed on their species' substrate or prey of choice. Feeding is the main purpose of the larval stage to prepare for pupation. Once their larval stage is complete the tree dwelling species make their way to the bottom of the tree to pupate. The pupal stage can last from 6 weeks to one year depending on the need to overwinter, and how short the overall lifecycle is for a particular species. A majority of clerid species pupate in earthen cells which are made from soil and certain enzymes secreted from their mouths. The rest remain in pupal cells. Adult beetles emerge from pupation and spend a variable time of their life maturing, and eventually oviposit. Sexually mature adults or imagos of Thanasiumus sp. overwinter inside the wood-borer-infested trees and oviposit during the spring.