Table 1.

Mass-scaling exponents for tracheal system parameters measured throughout ontogeny.

Parameter	Scaling exponent	Species	Developmental stages covered	References
air sac volume	1.38	Schistocerca americana	First instar to adult	(Greenlee et al. 2009)
tracheal system volume	1.3	Schistocerca americana	First instar to adult	(Lease et al. 2006)
thoracic tracheal diameters	0.22, 0.27, 0.25, 0.32	Manduca sexta	larval instars 2–5	(Greenlee et al. 2013)
tracheal system volume	1.04	Manduca sexta	larval instars 3–5	(Callier and Nijhout 2011)
	0.94	Manduca sexta	larval instar 5	(Helm and Davidowitz 2013)
tracheal diameters	0	Drosophila melanogaster	larval instars	(Henry and Harrison 2004)