2 | MATERIALS AND METHODS

2.1 | Specimens

Lady beetles, H. axyridis were collected in Suzhou (China) in August 2023. They were anaesthetized at room temperature using ethyl ether and killed with an overdose. For investigation of the morphology of wing cross sections, three right hindwings of male H. axyridiswere cut through at the wing base and removed from their bodies.

2.2 | Corrugated airfoil

The right hindwing of H. axyridis was cut into nine sections transversely along chordal direction using a scalpel. Each cross-sectional profile position was recorded as l/L withl being the distance between the cross section and the wing base, and L being the total wing length. The cross-sectional chord was denoted as c . Furthermore, the reference velocityvr was taken to be 1 m/s. The air densityρ was taken to be 1.225 kg/m3 and the air viscosity \(\mu\) was taken as 1.7894×10-5 Pa·s. The Reynolds number for these cases was calculated asRe=ρυrc /μ . As shown in Figure1(a), theRe with the l /L length between 0.1 and 0.8 is greater than 102, and the higher Re range is between 0.2 and 0.6. So, the cross sections 0.2, 0.4, and 0.6 are selected to research.
Three selected cross sections are shown in Figure 1(b). These cut of cross section were horizontal and smooth. Morphologies of cross sections were observed by the 3D microscope system (VHX-6000, Keyence, Japan), as show in Figure 1 (c). The geometry profile models of the three 2D corrugated airfoils (CA model) were established through the combination of hand-held probe three-coordinate measuring instrument (XM-T1200, Keyence, Japan) and AutoCAD software, including airfoil profile 1 (AP1), airfoil profile 2 (AP2) and airfoil profile 3 (AP3), as shown in Figure 1(d) and 1(e).