Palpigradi utilize their pedipalps for locomotion and some have three pairs of abdominal lung-sacs.
Unusually, however, palpigrades use their pedipalps for locomotion, so that the animal appears to be walking on five pairs of legs. Some palpigrades have three pairs of abdominal lung-sacs, although these are not true book lungs as there is no trace of the characteristic leaflike lamellae which defines book lungs. 
