Functional Wing Morphology and Aerodynamics of Panorpa Germanica (Insecta: Mecoptera)

Abstract

ABSTRACT The functional wing morphology of the wings of the scorpion fly Panorpa germanica L. was investigated using a combination of light microscopy, high-speed cinematography, wing manipulation and mechanical testing. In rising forward flight the wings are flapped 40° out of phase along a shallow stroke plane, the forewings leading. Aerodynamic analysis suggests that unsteady effects are important in flight. During the downstroke, both wings are straight and cambered, the chord being parallel to the body axis, which is angled 45° upwards from horizontal. Both wings are supinated at lower stroke reversal, the hindwing to a much greater extent, and flex ventrally halfway along their length for the first half of the upstroke. Flexion is parallel to the chord in the hindwing, but is oblique in the forewing, so distal forewing areas are supinated relative to proximal areas. The behaviour of the wings is related to their structure. Spars at the leading and trailing edges of both wings support the wing during the downstroke, and flexion during the upstroke is facilitated by buckling of the weak ventral thyridium region. The oblique flexion seen in the forewing is due to its relatively longer leading edge spar. The differences between the wings are, in turn, related to their pitch control mechanisms. The forewing has a well-developed clavus, like that of the forewing of a locust, and pitch is altered by relative movement of this and the leading edge, but only within a narrow range. Oblique flexion is necessary to invert the aerofoil. The weaker and less well-developed clavus of the hindwing, more similar to that of the Diptera, allows a greater degree of supination, effected largely by wing inertia. No oblique flexion is necessary.