Comment: Feedback Physics World  March 2018

More on midges

In response to Jennifer Ouellette’s feature “Sounding out swarms” (February 2018) in which she looks into swarming midges and the unusual characteristics of their collective behaviour.


Congratulations on a really accessible, fun-to-read, balanced article. I found the feature fascinating, but it’s a pity you did not have room to mention my work on the modelling of Nicholas Ouellette’s swarms, which was recently published in the Journal of the Royal Society Interface. Nicholas emphasized that models must now be able to capture both the intricate dynamics of swarms and the emergent “material”’ properties of swarms. My model predicts many of Nicholas’ intriguing observations, including the emergence of solid-like mechanical properties and the co-existence of core condensed phases surrounded by dilute vapour phases. And it may account for the stark differences in swarming behaviours observed in the stillness of the laboratory and under natural conditions.

The strong correlations seen outdoors may help swarms resist environmental disturbances. Intriguing connections have also made with self-gravitating systems like clusters of stars and with Gerber’s long-forgotten theory of speed-dependent gravity. This all stems from the simplest of model ingredients, the swarm’s aerial density profile and its velocity statistics.

Andy Reynolds

Rothamsted Research, Harpenden, UK