The barnacle larval stage that searches for a permanent surface is the cyprid.
A fertilized barnacle egg develops first into a nauplius larva. After several moults, the nauplius transforms into a cyprid, the second and final larval stage before adulthood. Unlike the feeding nauplius, the cyprid generally does not feed; it relies on stored energy while searching for a suitable place to attach.
Using modified antennules, the cyprid explores surfaces and assesses factors such as texture, chemistry, colour, wettability, and microbial biofilm. It eventually attaches head-first and secretes a powerful cement. After permanent settlement, it metamorphoses into a juvenile barnacle.
This life cycle explains how an animal that becomes permanently sessile can spread widely as a planktonic larva. Barnacles are crustaceans, despite their shell-like appearance and their historical classification as molluscs. The distractors are larvae or structures associated with other marine animals: trochophores occur in several worm and mollusc lineages, veligers are molluscan larvae, and planulae are cnidarian larvae.