Biologists explain that spiders in Brazil are engaging in a rare mating ritual that creates the illusion of 'spider rain'. The spiders are not actually falling from the sky but are suspended in a large, almost invisible web. This collective mating ritual increases genetic diversity and resistance to diseases in the offspring. Some species of spiders exhibit this social behavior of forming colonies, which benefits the food supply for the offspring and juveniles. While rare, similar events have been witnessed in Brazil in the past.