Lubrication in the joints of insects (Arthropoda: Insecta)

Abstract

AbstractFemoro‐tibial leg joint, head–prothorax joint (gular area) and occipital region of the head were examined using scanning electron microscopy in insects from the orders Blattodea and Coleoptera. Lubricating substances and corresponding pore openings were found in Argentinean Wood Roach Blaptica dubia and in the beetles from families Carabidae, Hydrophilidae, Silphidae, Scarabaeidae, Elateridae, Tenebrionidae and Curculionidae. Lubricant on the contacting surfaces were found on femoral and tibial counterparts of leg joints of different beetle species and cockroaches, in the gular region of the head in beetles, and in the occipital region of the head of the cockroach. Typical pore opening was on an average 1 µm in diameter (ranging from 0.5 µm to 10.0 µm). The amount of pore openings in a joint varies from a few pores to hundreds. The lubricant is found to be strongly variable in its appearance usually in the form of a single elongated filiform flow, as well as long or short drops, often forming accumulations or spreading over the surface. The supposed function of the lubricant in studied joints is discussed and assumed as friction and wear minimization. The presence of a high amount of the lubricant in leg joints of insects with intense leg locomotion is presumed.