Figure 3. Effect of dilution on the viscoelastic properties of the digestive fluid.

The red dotted vertical line materializes the abrupt transition in capture rate for insects (see Fig. 1b). (a) Extensional viscosity (white squares) and shear viscosity (white circles) of the pure fluid and diluted solutions, normalized by the shear viscosity of water (solid line, η ^water = 0.0012 Pa.s, measured in the same condition). Shear viscosity is plotted for  = 40 s⁻¹ and extensional viscosity is plotted for E = 4, the typical shear rate and extensional strain of the fluid imposed by insect motion respectively. (b) Elastic relaxation time λ of the pure fluid and diluted solutions (M±min-max of 10 fluids from 10 pitchers of 7 plants).