Flight efficiency is a key to diverse wing morphologies in small insects

Area of Science:

• * Aerodynamics and biomechanics of insect flight.

Background:

• * Insect wings are typically hybrid structures of veins and membranes.
• * Smallest flying insects often have bristled wings instead of membranes.
• * The reason for this structural diversity in wing types across insect sizes is not well understood.

Purpose of the Study:

• * To investigate the aerodynamic efficiency of insect wings with varying structures.
• * To determine if aerodynamic efficiency, rather than force production, explains the diversity of wing structures in insects.
• * To explore the impact of Reynolds number on the efficiency of different wing types.

Main Methods:

• * Computational fluid dynamics simulations of flapping wings.
• * Testing wings with structures ranging from fully membranous to sparsely bristled.
• * Analysis of wing kinematics and aerodynamic performance at different Reynolds numbers (Re).

Main Results:

• * Reduced aerodynamic efficiency with decreased wing surface solidity is less pronounced at low Reynolds numbers (Re = 4) compared to higher ones (Re = 57).
• * Bristled wings incur smaller energetic costs for flight in small insects than in large insects.
• * Small insects can achieve similar flight efficacy with either bristled or membranous wings.

Conclusions:

• * Aerodynamic efficiency, particularly at low Reynolds numbers, explains the prevalence of bristled wings in small insects.
• * Larger insects necessitate membranous wings for efficient flight force production.
• * These findings have implications for insect fitness, dispersal, and energy expenditure during flight.