Swarms of femaleAnopheles gambiaemosquitoes may fracture when perturbed

In contrast with bird flocks, schools of fish, and migratory herds that display directed motion, mating swarms of male insects do not possess global order. Over the last decade or so, substantial progress has been made in quantitatively demonstrating the collective nature of these swarms. Their emergent collective behaviour cannot be determined by passive observations alone; instead, they must be perturbed. Here I identify a new putative emergent property of swarming by modelling the first detailed experimental studies of swarms of female insects. I show that swarms of femaleAnopheles gambiaemosquitoes are predicted to undergo cohesion-to-fragmentation (order-to-disorder) transitions and so are prone to disintegration in the face of environmental perturbations. This may explain why it is difficult, if not impossible, to observe pure female swarms ofAnophelesmosquitoes in the wild. More generally, the new results may explain why most natural swarms of insects fit into one of two classes, namely uniformly distributed and clumped, which are the extremes of a continuum.