 Lyon &amp; Colyvan 2008 also contains a much discussed example from evolutionary biology. Why do hive-bee honeycombs have a hexagonal structure? The nature of the question is contrastive: why hexagonal as opposed to, say, any other polygonal figure or combination thereof? Part of the explanation depends on evolutionary facts. Bees that use less wax and thus spend less energy have a better chance at evolving via natural selection. The explanation is completed by pointing out that ‘any partition of the plane into regions of equal area has perimeter at least that of the regular hexagonal honeycomb tiling’. Thus, the hexagonal tiling is optimal with respect to dividing the plane into equal areas and minimizing the perimeter. This fact, known as the ‘honeycomb conjecture’ was recently proved in Hales 2001 (see also Hales 2000). The explanation of the biological fact seems to depend essentially on a mathematical fact. Just like the cicada example, this case has been extensively discussed in the literature. 