What is the difference between trachea and spiracles

Access to Document Link to publication in Scopus. Fingerprint Dive into the research topics of 'Tracheal System'. Together they form a unique fingerprint. View full fingerprint. In Encyclopedia of Insects pp. Elsevier Inc.. Encyclopedia of Insects. Elsevier Inc. Harrison, J , Tracheal System. Harrison J. In Encyclopedia of Insects. Harrison, Jon. From the main trunks, tracheoles pass throughout the body. The tracheae open to the air at the paired spiracles.

There is one pair per segment in the thorax and also in the first nine abdominal segments. This arrangement does vary with different species. In most species the spiracles on the first segment of the thorax are missing. The pair on the ninth abdominal segment is also missing. The tracheoles end within the body cells. Gases move by diffusion within the tracheal system.

When the insect is less active the ends of the tracheoles contain fluid. As activity increases, the fluid is removed from the tracheoles. This means that the exchange of gases occurs nearer the cells.

In the extreme case of fatigued flight muscle, the exchange interface lies within the muscle cells. Diffusion alone does not meet the respiratory demands of the animal. Gases are moved, to a large extent, by pumping actions of the body segments.