An experimental study of free flight kinematics in a miniature parasitoid waspTrichogramma telengai

Abstract

AbstractBody size is the major factor to the flight mechanics in animals. To fly at low Reynolds numbers, miniature insects have adaptations in kinematics and wing structure. Many microinsects have bristled wings, which reduce inertia and power requirements when providing good aerodynamic efficiency. But both bristled and membranous-winged microinsects fly at Reynolds numbers of about 10. Yet, the kinematics of the smallest known membranous-winged species have not been studied sufficiently. The available data are limited to the forewings of a relatively large parasitoid waspEncarsia formosa. We studied kinematics of wings and body and flight performance in one of the smallest membranous-winged wasps, Trichogramma telengai (0.5 mm body length,Re= 12).T. telengaireaches 29 cm s-1speed and 7 m s-2acceleration in horizontal flight which are comparable with the flight performance of other microinsects. The wingbeat cycle is characterized by high frequency (283 Hz) and stroke amplitude (149°) and includes U-shaped strokes at high angles of attack and prolonged clap-and-fling. The hindwings move with a slight phase shift and smaller amplitude than the forewings.T. telengaidiffers from large membranous-winged insects and miniature featherwing beetles in kinematics, but it is fundamentally similar toE. formosa(Re= 18, membranous wings) and thripsFrankliniella occidentalis(Re= 15, bristled wings). We showed that, atRe≈ 101, both membranous and bristled-winged insects have sufficient flight performance. Further study of the bristled-winged insects will make it possible to define the size limits of effectiveness of different wing structures.