Larval development of the serpulid polychaete worm, Hydroides dianthus Verrill 1893
parallels that of other closely related species. The larvae prefer to settle upon surfaces already
inhabited by other members of their own species rather than to colonize surfaces without such
conspecific residents. However, very wide variations in the intensity of settlement are observed. These
differences in the amount of settlement cannot presently be attributed to any single variable. Gregarious
settlement appears to be typical for sessile species which do not have the ability to reproduce
asexually after settlement.