insects ventilations

spiracles

small openings on the surface of insects that allow for the exchange of gases with their environment

sphincters

rings of muscles which surround the openings to spiracles. They control the size of the opening to maintain a balance between gas exchange and water loss

How does gas exchange

They have a rigid exoskeleton, which is waterproof to prevent the insects drying out, but it also prevents gas exchange. Insects increase their rate of gas exchange by having openings in the exoskeleton called spiracles, which lead to a network of tubes called tracheae, which branch into many smaller tracheoles that carry air directly to the cells. These tracheae and tracheoles are held open by rings of hard chitin (a polysaccharide). The tracheoles penetrate deep into the insects tissues, carrying air quickly and directly to every cell. At the ends of the tracheoles oxygen diffuses directly into the cells, and carbon dioxide diffuses out, down their concentration gradients.

1. spiracles in exoskeleton

2. spiricals

3. trachea

4. rings of chitin

5. air sac

6. tracheoles

7. muscle cell

How does ventilation differ between small insects and larger

Small insects can rely entirely on diffusion through the tracheoles to obtain enough oxygen for respiration, but larger and more active insects, like houseflies and grasshoppers, ventilate their tracheal system by using muscles to squeeze their abdomen and so suck air in and out of the spiracles. This increases the concentration gradient and so the rate of gas exchange

what are some issues that open spiracles cause

water loss

how do you counter the problem of water loss

To counteract problems of water loss insects can close their spiracles using a muscular valve. The opening and closing is controlled by the nervous system, which detects a build-up of CO2 in the tracheae. Some insects also have spines or hairs around the spiracles to increase humidity and so reduce evaporation.

1. closed

2. open