Tracheole

Tracheoles are about 1 μm in diameter, and they convey oxygen to cells while providing a means for carbon dioxide to escape.

This increases the surface area for gas exchange in the insect.

Areas of intense metabolic activity, such as the digestive tract and flight muscles, have very dense aggregations of tracheoles.

Unlike the larger tracheae which are derived of ectodermal stem cells, tracheoles do not molt with the insect.

Instead, they remain in place and fuse themselves to new tracheae at each molt by a cement they produce.