1. RESPIRATORY SYSTEM(TRACHEAL SYS.)
Gas exchange
Responsible for delivering oxygen and removing Co2
Insect blood doesn’t contain haemoglobin
Has massive plumbing with tubes carry air to cells: TRACHEAL SYSTEM

2. SPIRACLE
Located on the thorax and abdomen
One pair of spiracle per segment
Opening with muscles, allows air to enter
minimize water loss
Mechanism of opening and closing of spiracle muscle:
Co2 high in body muscles relax  spircales open Co2 escape + Oxygen in
when O2 in body approx. outside  muscles contract  spricales pull shut

3. Eg: muscles cells: tracheols enter deep into the cells: close to mitchondria (where o2 needed)
GAS (outside)spiracles tracheal trunk (primary trachea) 2o & 3o trachea tracheole

4. AQUATIC ADAPTATION BIOLOGICAL GILLS
mayflies and damselflies, the gills are leaf-like in shape and located on the sides or rear of the abdomen. 
Stoneflies and caddisflies have filamentous gills on the thorax or abdomen. 
Dragonflies differ from other aquatic insects by having internal gills associated with the rectum.

5. Breathing Tubes
Snorkel-like
a tube with spiracles- the tube above water for air intake
Water bubble (DIVING BEETLE)
carry a bubble of air with them whenever they dive beneath the water surface