Baetidae is a family of mayflies with about 900 described species distributed worldwide. These are among the smallest of mayflies, adults rarely exceeding 10 mm in length excluding the two long slender tails and sometimes much smaller, and members of the family are often referred to as small mayflies or small minnow mayflies. Most species have long oval forewings with very few cross veins (see Comstock-Needham system) but the hindwings are usually very small or even absent. The males often have very large eyes, shaped like turrets above the head (this is known as "turbinate condition").