Araneae: Salticidae
Hypoblemum albovittatum
The two spiders fall from their position, restrained by a thread of silk that the female had anchored herself with.
This is a tricky business. The male holds the female with his legs. Her thorax is turned one way, in which position she cannot bite him, and her abdomen is twisted the other in which position he can use his palps to inseminate her.
Some pulsating movement takes place for what seems like an age and I start to suspect that perhaps someone is being eaten.
But I am wrong.