Question

Insect tracheal system opens to the outside through_______.
A. Spiral value.
B. Pecten.
C. Spiracle.
D. Taenidia.

Answer 1

Hint: Insect tracheal system which is also meant as the respiratory system of insects. Here, it produces the respiratory gases to the interior and performs exchange of gases. It can be found based on the tracheal system in the body of insects. In this system, it is well defined and through this we can analyze it.

Complete answer:
Most invertebrates, including insects, exchange oxygen and carbon dioxide between their tissues and air by a system of air-filled tubes called tracheae. It is also called the windpipe which is a cartilaginous tube that connects the larynx to the bronchi of the lungs that allows a passage of air.
The following are those which are involved in the tracheal system. They are as follows:
PECTEN:
This is a comb-like structure which occurs in animal bodies.
It is a pigmental vascular projection from a choroid in the eye of the bird.
The following are scientific names, phylum, class, order, rank of pecten. They are as follows:

HIGHER CLASSIFICATION	Scallop
SCIENTIFIC NAME	Pecten
PHYLUM	Mollusca
CLASS	Bivalvia
ORDER	Pectinidia
BIOLOGICAL RANK	Genus

TAENIDIA:
These are the circumferential thickening of cuticles in the insect respiratory system.
It generally takes up the form in spiral and hoop thickening of the cuticle.
The geometry varies across different orders and throughout the tracheae in individual organisms.
SPIRACLES:
Tracheae opens to outside through small holes known as spiracles.
These are insects for some apterygota and larval.

So, from the above, it is clear that the correct answer is Option C.

Additional Information:
The following are some of the parts which are guarded by spiracles. They are as follows:
> The valves which are controlled by muscles enable the grasshopper to open and close them.
> There are hairs that filter out dust as they enter into them.

Note:
 Spiracles open into tracheal tubes. This leads to finer branches. These branches penetrate to every part of the body. At their extreme ends they are called tracheoles. The size may be less than I micrometer in size.