The direct transport of oxygen in insects by large tracheae.

Vast numbers of large and small tracheae in the abdomen of adult Calliphora are so modified that they can transfer oxygen directly by diffusion to the developing ovaries. Tracheoles are scarce but. instead, a system of distended tubules, evaginated into the cytoplasmic surface of the trachea, cover the entire tracheal surface with permeable tubes diffusing oxygen to the developing tissues. A similar development occurs also in the male fly.