Synopsis Animal world is very colourful and have a varied form of nature and behavioural characteristics that live on dry land some take in air and emit it. These phenomenas are termed inhalation and 'exhalation'; for instance, man and all such land animals are furnished with lungs, others, again, do not inhale air, yet live and find their sustenance on dry land; as, for instance, the wasp, the bee, and all other insects. Some animals at first live in water, and by and by change their shape and live out of water, as is the case with river worms, for out of these the gadfly develops.