Figure 2 in Mechanisms preventing animals to achieve buoyant flight

Figure 2. Animal buoyancy across theoretical conditions of body cavity size and density differential relative to the environment. Coloured symbols and lines represent median values of Oeda species with thoraxes filled with sun-heated air. Dotted lines depict density differentials with cavities filled with air, methane, and hydrogen at a presumed physiological thermal limit of 15°C above the environment (Hoffman et al. 2013). The y-axis points at which dotted lines intersect with the limit of the black area represent the buoyant cavity volumes necessary to overcome the body weight. Calculations based on reference conditions of environment temperature of 15°C and air density of 1.225 kg/m3.