How in the world are flies beneficial??

Flies are annoying. And gross. And they drive people crazy. They carry disease and they are EVERYWHERE when the weather gets warm! So what purpose do they serve? According to sciencing.com:

“As unappealing as they seem, flies and their larvae are part of nature's cleanup crew. Blow flies, for example, lay their eggs in rotting carcasses. The maggots feed on the decomposing flesh, helping break the organic material into its components. Their digestive processes release the nutrients back into the soil. Other flies lay their eggs in manure so their maggots can feed, breaking down the manure. These decomposers complete the food chain, releasing nutrients for plants, bacteria and fungi to use.”