Question: what happens to the spiricles when the spider is on the water?

Fen Raft Spider answered on 23 Nov 2017:

I breathe through my spiracles and so need them to have access to air at all times. This is easy enough when I am skating across the water, as they are on my abdomen (back segment) and so are sticking out of the water into the air. When I dive into the water to catch food or escape from predators the hairs on my abdomen actually allow me to breathe! These hairs repel water and so trap air in a bubble around my body, allowing me to breathe as normal.