Gall aphids: Nature’s waste-disposal system
The aphid Pemphigus spyrothecae lives in galls which helps prevent attacks from predators. Soldier aphids remove waste from the galls by pushing or rolling balls of defecated honeydew out of the entrance to the gall.
The balls of honeydew are liquid marbles created by coating the honeydew in a powdery wax secreted by the aphids. The wax is hydrophobic and creates a microscopically rough surface on the inner wall of the gall. Weakly compacted needles of this wax render the surface superhydrophobic.
See here for details of how we can create liquid marbles in the laboratory using hydrophobic sand.
- Altruistic housekeeping in a social aphid T.G. Benton and W.A. Foster, Proc. R. Soc. Lond. B 247 (1992), 199-202
- Defecation behavior and ecology of insects M.R. Weiss, Annu. Rev. Entomol. 51 (2006), 635-661
- How aphids lose their marbles N. Pike, D. Richard, W. Foster and L. Madhadevan, Proc. R. Soc. Lond. B 269 (2002), 1211-1215