Polarised light micrograph of a mayfly larvas caudal filaments. These structures resemble long, hair-like fibres, extending from the tip of the larvas abdomen. They facilitate respiration as they increase the surface area for oxygen absorption. Mayflies belong to the order Ephemeroptera, which also includes dragonflies and damselflies. There are over 3,000 species of mayflies, and they can be found in various aquatic environments. Magnification: 186x when printed 10 centimetres wide.