Oxygen supply through the tracheolar–muscle system does not constrain insect gigantism

. Here we contest this hypothesis by showing that the relative space occupied by tracheoles in the flight muscle of insects (1) increases by only 1.8-fold over a 10,000-fold body mass range (1,320 micrographs, 44 species, 10 orders), (2) is typically 1% or less in most species, and (3) that this observation holds when we extend our relationship to the long-extinct gigantic dragonfly-like Meganeuropsis permiana (approximately 100 g). The small space requirement and the lack of a strong increase in tracheolar investment with body size, despite clear evolutionary potential to do so, provide convincing evidence that diffusive oxygen transport through the tracheolar-muscle system does not constrain the maximum body size of extant or gigantic prehistoric insects.