Why are two flies entangled?

When mating, at a suitable temperature, the male housefly can mature and mate 24 hours after emergence and 30 hours after emergence of the female housefly. The mating time is usually from 5 am to 7 am. Sensitive sense of smell, sex pheromone and vision are all important factors to promote the mating of male and female flies. A pair of mating houseflies can stay in one place for a long time, crawl and fly together, and the effective mating time is as long as 1 hour. Most houseflies mate only once in their lives. The semen of a male fly can be stored in the fertilization sac of a female fly for a long time, which can stimulate oviposition and keep the fly eggs fertilized for 2-3 weeks without mating with another male fly.