Q. Which of the following is not a part of the respiratory system of Periplaneta americana?

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Solution:

Respiratory system (tracheal system). It is well-developed and consists of:
Network of trachea. Tracheoles (thin branching tubes) Spiracles (10 pairs).
Trachea forms a network and its branches reach to every part of the body without involving the circulatory system. Body tissues receive the oxygen by diffusion from the tracheoles.
Spiracles are equivalent to the nostrils of the human through which the tracheal system open outside to atmosphere. First thoracic and abdominal spiracles remain always open while other are guarded by sphincters or valves. Sclerites are chitinous plates covering the segments - 2 pleurites (lateral), 1 tergite (dorsal) and 1 sternite (ventral). These sclerites are joined together by arthrodial membrane which is a thin and flexible articular membrane.