In Periplaneta americana,

With the help of several ommatidia, a cockroach can receive several images of an object. This kind of vision is known as mosaic vision with more sensitivity but less resolution, being common during night (hence called nocturnal vision).Malpighian tubules which help is excretion. Digestive enzymes are secreted by hepatic caecae.Exchange of gases take place at the tracheoles by diffusion.The blood is colourless as it is devoid of pigment.