Haller's organ
Haller's organ is a complex sensory organ possessed by ticks. Ticks, being an obligate parasites, must find a host in order to survive; via olfaction and the sensing of humidity, temperature, and carbon dioxide, Haller's organ detects them. Haller's organ is a minute cavity at the terminal segment of the first pair of a tick's legs. Each one is composed of a pit and a capsule, which contain sensory setae.
