Bees and wasps use the same architectural solutions to join large hexagons to small hexagons

Newswise — Bees and wasps have converged on the same architectural solutions to nest-building problems, according to a study by Michael L. Smith in the Department of Biological Sciences at Auburn University, US, and colleagues, publishing July 27^th in the open access journal PLOS Biology.

Both honeybees and social wasps build nests made up of hexagonal “cells” where they raise their young and store their food. While they use different materials to build their nests, bees and wasps have independently evolved this hexagonal comb structure because it is the most efficient use of space and building materials. However, in some species of both bees and wasps, queens and males are larger than workers, and so need larger cells, creating a problem – cells of different sizes don’t fit snuggly together in the comb. The researchers analyzed photographs from the nests of five honeybee species and five wasp species, containing a total of 22,745 cells. They found that the size difference between these specialized reproductive cells and worker cells ranged from zero in the wasp Metapolybia mesoamerica, up to drone cells in nests of the honeybee Apis andreniformis that were 2.7 times larger than worker cells. The bigger the difference, the bigger the architectural problem.

The researchers found that wasps and bees used similar building techniques at the transition between small and large cells: if the size difference was minor, the insects built intermediate-sized hexagonal cells in between, but when the size difference was more pronounced, they built pairs of five- and seven-sided cells at the join. A mathematical model of the hexagonal comb structure generated a similar pattern of intermediate-sized and pentagonal/heptagonal cells at the transition between different cell sizes, indicating that the observed structure is based on fundamental geometric rules.

These results show that, despite 179 million years of independent evolution, honeybees and social wasps have converged on the same geometric solutions to the architectural challenge of building nests that can accommodate young of different sizes, the authors say.

Smith adds, “We went into this project not knowing what we'd find, but seeing that all these hexagon-building collectives have arrived at the same architectural solutions is amazing. These groups independently evolved hexagonal-cell building, and are separated by 179 million years, and yet, they've converged on the same architectural tricks.”