1. All of the wing fringe cilia of Thrips physapus, except those along the hindwing leading edge, pivot in elongated sockets which lock them into two positions. 2. The wings lie parallel over the abdomen when not in use, with the cilia locked in the closed position at an angle of 15-20° to the wing axis. The closing of the fringes prevents entanglement of the trailing edge cilia and lateral projection of the forewing leading edge cilia. 3. During flight the cilia are locked in the open position, doubling the wing area. The locking force is stronger than the combined aerodynamic and inertial forces on the cilia. 4. The fringes are opened by abdominal combing and closed by tibial combing. 5. The same morphological features are found in other members of the sub-order Terebrantia. Parallel wings at rest are characteristic of this suborder, and the collapsible fringe system is viewed as an effective method for parking the wings. 6. The fringes of the sub-order Tubulifera are not collapsible. The wings overlap on the abdomen at rest and a similar parking problem does not arise.
