Why do flies gather and swarm in front of doors with alcoves?

Flies are attracted to doors with alcoves due to the sheltered environment these spaces provide, which offers protection from wind and predators. Additionally, these areas may trap odors or attractants, such as food or moisture, that draw flies in. The warmth and light near entrances can also entice them, as they seek out favorable conditions. This behavior is a natural instinct for finding resources and suitable habitats.