Why Flies Land on People

The highly anticipated American vice-presidential debate, which took place on October 7th, instantly went viral – not due to both debaters' performances, but rather because of an insect incident. As Vice President Mike Pence responded on law enforcement issues, a fly circled around and eventually sat on his perfectly-trimmed white hair; making a distinctive contrast and stealing the show for two minutes straight. Jokes aside, there is scientific evidence that suggest that landing on humans is a part of flies' instinct.

Despite the unremarkable size of the fly, its origins have developed over millions of years. Throughout these years, this small insect has revolutionized a sensitive heat-detecting system and a tube-like mouthpart. As the ecosystem evolved, so did the flies, as their species adapted to the changing and challenging environment.

It is easy to comprehend that flies are scavengers and locating food sources is their priority. Therefore, the following factors are highly likely contributing to a flies' appeal to humans: the carbon dioxide humans release, micro-food particles on exposed skin, heat, sweat and many other factors.

First, the carbon dioxide humans exhale is tempting to flies as they recognize the association between the gas and long-distance food sources. They are able to trace and feast on whatever humans leave behind. Furthermore, if any tiny food particles are pinpointed by the fly, it would land, vomit to liquefy the food, and then finally suck up its meal. Frankly, that is what a fly does when it senses food on a person and lands. Secondly, flies may breed faster in a warm environment; hence, the buildings, which radiate heat, are their prime target; where there is a steady room temperature, there are food sources. Astonishingly, sweat is one of the flies' interests as well. In a fly's view, sweat is a sort of sustainable food source with an abundant amount of sugar, salt, proteins, and carbohydrates.

With all potential causes explained above, the true reason of why that particular fly landing on Pence's head remains a mystery. Whatever people say about this incident, it has indeed become the world‘s most famous fly.

Written by Yuning Gu