Abstract
Butterflies can directly absorb heat from the sun via their wings to facilitate autonomous flight. However, how is the heat absorbed by the butterfly from sunlight stored and transmitted in the wing? The answer to this scientific question remains unclear. The butterfly Tirumala limniace (Cramer) is a typical heat absorption insect, and its wing surface color is only composed of light and dark colors. Thus, in this study, we measured a number of wing traits relevant for heat absorption including the thoracic temperature at different light intensities and wing opening angles, the thoracic temperature of butterflies with only one right fore wing or one right hind wing; In addition, the spectral reflectance of the wing surfaces, the thoracic temperature of butterflies with the scales removed or present in light or dark areas, and the real-time changes in heat absorption by the wing surfaces with temperature were also measured. We found that high intensity light (600–60,000 lx) allowed the butterflies to absorb more heat and 60−90° was the optimal angle for heat absorption. The heat absorption capacity was stronger in the fore wings than the hind wings. Dark areas on the wing surfaces were heat absorption areas. The dark areas in the lower region of the fore wing surface and the inside region of the hind wing surface were heat storage areas. Heat was transferred from the heat storage areas to the wing base through the veins near the heat storage areas of the fore and hind wings.
Highlights
Sunlight is the most important source of energy and it supports the survival and reproduction of most creatures on Earth
We found that when the light intensity was above 40,000 lx, the equilibrium temperature could rapidly exceed 70 C, which was much higher than the butterflies could tolerate, and exposure to a light intensity above 40,000 lx caused the death of the butterflies half an hour after the experiment finished
1A-Cu2, Cu1-Cu2, M3-Cu1, and R2-M1 on the hind wings compared with other wing areas during lighting from 300–540 s. These results indicate that the dark areas in the mid-posterior region near the wing base in wings cells A-CU3 and Cu2-Cu3 on the fore wings, and wing cells 1A-Cu2, Cu1-Cu2, M3-Cu1, and R2-M1 on the hind wings were the temporary heat storage areas on the wing surfaces (Figure 3 & Figure 7)
Summary
Previous studies have shown that butterflies must directly absorb the heat from sunlight to increase their thoracic temperature above that of their surroundings in order to allow autonomous flight to occur When adult butterflies require heat for autonomous flight, they adjust their body posture and either fully expand their wings or angle them to allow the optimal absorption of sunlight, where the heat absorbed is transferred to the thoracic muscles to enable flight (Heinrich, 1990; Huey et al, 2003). Some studies indicate that the angle of the incoming sunlight and the wing opening angle can both significantly influence the rate and amount of heat absorption in butterflies (Plattner, 2004; Shanks et al, 2015; Niu et al, 2016). Heat absorption is important, but it has to be modulated via behavior to avoid overheating (Kingsolver, 1985)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
