John A. Fornshell Department of Invertebrate Zoology, United States National Museum of Natural History, Smithsonian Institution, Washington D.C., USA Arthropods ISSN 2224-4255 http://www.iaees.org/publications/journals/arthropods/online-version.asp 2017 6 1 1 7 International Academy of Ecology and Environmental Sciences Hong Kong 12 November 2016 7 January 2017 1 March 2017 Nymphon charcoti Protonymphon Pycnogonida The protonymphon larva and next four instars of the pycnogonids Nymphon charcoti are described. The developmental pattern is that of a "Typical Protonymphon" according to Bain's 2003 classification. The description is based on archived specimens from the National Museum of Natural History collections. The walking legs appear initially as underived buds with three pseudo-segments beginning with walking leg one in the second instar. In the subsequent instars the walking legs appear as six segmented appendages and then eight segmented appendages. In the genus Nymphon there are four different post embryonic developmental patterns, "Typical Protonymphon", "Attaching Larva", "Lecithotrophic Larva" and "Elvie's Larva". This diversity of developmental patterns within the same genus which is not restricted to the Nymphonidae indicates that the developmental patterns as currently defined in the literature have little phylogenetic relevance. DOI 10.0000/issn-2224-4255-arthropods-2017-v6-0001 http://www.iaees.org/publications/journals/arthropods/articles/2017-6(1)/larval-stages-Nymphon-charcoti-Bouvier-1911.pdf