Experimental investigations on the strategies of fighting crickets Velarifictorus micado to manipulate air resistance

Fighting crickets, one species of flightless insects optimally chosen by nature for millions of years, have evolved to fairly smooth and streamlined body surfaces. This article tries to answer the question how the insects manipulate air resistance when travelling through air after take-off without using their wings and meanwhile keep a high efficiency. We found that fighting crickets, Velarifictorus micado, performed two types of movements through air: stable and unstable. The two types both have a high moving efficiency. For the stable type, the moving efficiency is larger than 95%. As a typical example, focusing on the stable type, we firstly predicted each component of aerodynamic drag applied on the crickets and analysed the drag contributions to the initial kinetic energy dissipation. Further investigation revealed the mechanisms of the efficiently moving strategy against air resistance for the insects. The results show that the crickets can spin their hind legs to adjust body posture, thereby changing (increasing or decreasing) the air drag acting on the body to raise the efficiency during aerial movements. This work may advance the understanding of the significance of hind legs to insects’ evolution and provide inspiration for future robot or micro aerial vehicle designs.