Flies taste things with the help of their feet. They walk over almost all kinds of waste foods and plants, accumulating germ as they go. This is when flies become a health hazard; flies has the ability to carry bacteria and spread all types of horrible diseases among humans.
In the Biblical fourth plague of Egypt, flies epitomize death and decay.
Flies like the genus Hydrotaea and its larva (Maggots) are used in forensic cases to calculate the time of death for corpses.
The average house fly has a lifeline of about 15-25 days and longer in colder regions, but it lays approximately 3000 eggs in its lifetime – some on your food and theirs.
The idiom – someone would “not harm a fly” – means that a certain individual would be gentle and not hurt even the most irrelevant of animals. Far from being insignificant, the fly like the Tse Tse fly carries the deadly sleeping sickness and kills up to 9000 people per year as of 2010.
In food production, certain cheese ranges, such as Casu Marzu, are introduced to flies known as cheese skippers – the digestive activities of the fly larvae soften the cheese and improve the aroma as part of the process of maturation.