How Do Whirligig Beetle Larvae Breathe?

Strangely for insects that live their lives predominantly on the very surface of the water, whirligig beetle larvae actually have gills. They have a windpipe too and breathe air directly when they are on the surface. Their gills form growths on the side of their body and are an unusual feature for a beetle at any stage of its life cycle.

Because of their dual breathing system, whirligig larvae are just as happy swimming below the surface of the water, even though they prefer to be at the top. They can move quickly underwater and swim well and they get out of danger if threatened by immediately submerging and finding an underwater plant to cling to. When the danger passes, they come out and back to the surface.

When they are beneath the surface of the water, their gills use simple diffusion to absorb the oxygen they need from the water. Their blood takes oxygenated blood away from the gills to other parts of the body, and fresh oxygen diffuses in to the blood that then flows to the gills.