It happens to be the season when mosquitoes and flies go wild, but it is true that there are not as many flies as there are mosquitoes today. This has a lot to do with our improved sanitation today, after all, flies need to lay their eggs on manure pits and rotting food, while many rural toilets have now been converted to squatting, and the shorter disposal cycle for waste has greatly reduced their hatching.

It is proposed that birds originated from dinosaurs, and that "ancestor birds" are a transitional species between birds and dinosaurs.

The existence of reproductive isolation, so that these situations can not occur, even if there are some individuals of different species sometimes complete the mating, but they generally can not produce offspring, or produce offspring can not continue to reproduce