Haller’s organ

…by a sensory pit (Haller’s organ) on the end segment of their first of four pairs of legs. Eyes may be present or absent.

A sensory pit called Haller’s organ contains sensory setae and is found on the tarsal segment of the first pair of legs of all ticks (Ixodida). One to three pairs of eyes are present on the anterior of the idiosoma in Opilioacariformes, a few Astigmata, and many Ixodida and…