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All developmental stages of Tanystylum bealensis are described. This is the first complete developmental series of a pycnogonid species collected from a natural, rather than a laboratory-reared population. Development proceeds through a series of nine instars from egg to adult, with major defining characteristics of the instars being the addition of walking legs, loss of chelifores, and modification of larval appendages into adult palps and ovigers. All stages are free-living on the hydroid Plumularia setacea, except for the first instar (protonymphon), which remains on the ovigers of the adult male for a short time after hatching. Development in T. bealensis is compared to development in both the closely related species T. orbiculare and to the more distantly related Achelia alaskensis.

During the years 1980 to 1982, two common southern California pycnogonids, Anoplodactylus californicus Hall, 1912 and Ammothea hilgendorfi (Böhm, 1879) were routinely collected and kept in aquaria. Observations were made both in the field and in the laboratory on feeding behavior and other aspects of the behavior and biology of the two species. It was concluded that, of the two species, Anoplodactylus californicus would be a good candidate to raise in the laboratory for further studies on the biology of these organisms.