Larvae probably take at least a year to develop. Mouthparts are for chewing. Wood infested by these beetles is usually well decomposed and falls apart readily. Adult Passalus beetles are often covered by mites. Adults tend and feed larvae, preparing food with salivary secretions.
Food consists of decaying plant matter.
When disturbed, adults produce a squeaking sound by rubbing their wings on the abdomen. This is apparently used for communication between members of the colony. None, considered beneficial. For additional information, contact your local Texas extension service agent, or search for other state extension service offices.