A second ramus, the “exopodite,” often is also retained in the form of a palp or feeler.
This form is retained, with little alteration in some adult Copepoda, where the biramous “palp” still aids in locomotion.
A palp sprouts on the mandible and the median eye disappears.
Projecting from each side of the head of a butterfly is a fluffy structure, the palp.
The third one was ...