There are many species out there, but the most common ones are:
The House Fly – this small insect can be found all over the world, and can be recognized by the fourth wing vein being sharply angled and the four dark stripes on the top of its thorax. A female can lay 5-6 batches of 75-100 white oval eggs. If the weather is warm enough, these eggs can hatch in just 12-24 hours and start feeding on the source of food they were born in. These larvae will need 4 to 7 days to turn into adult flies, and they will be ready to mate as soon as they emerge. They like to lay their eggs on meat, animal manure, human faeces, garbage, decaying fruits or vegetables and others.
The Blow Fly – The adult has a shiny metallic colouring, with bodies that are either blue, green or black. They have bristles on their meron and a well-defined posterior calli. The name comes from an old English expression which said that meat with fly eggs on it was “fly blown”. Adults are attracted to flowers with odours that resemble rotting meat, and the larvae are scavengers of carrion and dung. They lay eggs on dead animals, and then the larvae feed on the decaying flesh. So these insects do play an important role in the ecosystem. Sterile blow flies were even used during the war in order to remove decaying tissue and prevent bacterial growth in open wounds.