by Heike Lutermann
Weight, volume and unbalancing: loading constraints of mud dauber wasps carrying mud balls
C. Polidori, M. Federici, L. Trombino, V. Barberini, V. Barbieri and F. Andrietti, 2009, J. Zoology, 279: 187-194
Architectural monuments such as the great pyramids of Giza have intrigued us for centuries or even millennia. Our enchantment with them is strongly linked to the skills of ancient architects that designed and executed such structures with such precision and without modern engineering technology. Thousands of workers were necessary to move the blocks used for these structures and the means employed to transport and fit them together are still a matter of debate.
The study by Polidori et al. (2009) looks at a very different sort of architect, mud-dauber wasps of the genus Sceliphron, that build mud nests to raise their offspring. Due to their small size their nests are likely to go largely unnoticed but this does not make them less extraordinary. Like the ancient architects these wasps are faced by the challenge to transport the building material to the building site. Unlike the Egyptian architects female mud dauber wasps master this task alone and have to transport the mud by air.
Polidori and colleagues show elegantly that the wasps adjust their mud loads to the physical limitations they experience and as a result larger individuals carry larger loads. While they do not appear to be constrained in their carrying capacity by the weight of the mud ball the volume of those balls corresponds remarkably well to the theoretically predicted volumes. These parameters affect the wasp’s ability to lift their load.
Furthermore, Polidori et al. (2009) found indications that the wasps take possible impairment to their flight abilities into account when collecting mud balls. In addition, they found evidence that the wasps adjust their mud balls to the physical properties of the soil that they are collecting from. The study by Polidori et al. (2009) is the first comprehensive one of this kind and they show that natural selection has equipped their tiny study subjects with noteworthy engineering skills that humans only achieve after several years of study.