can last 7 to 18 days, with the megalopa stage lasting 25 to 45 days. Colder water is associated with longer durations in each stage. During the larval stages, M. kaempferi is found near the surface, as the planktonic forms drift with ocean currents. This surface water ranges between 12 and 15 °C during the hatching season (January to March). This is much warmer than the waters at depths below 200 m, where adults are found, with waters steadily around 10 °C. Optimal temperatures have a 70% survival through the first zoeal stage, which is greatly reduced to a 30% survival in the second zoeal and megalopa stages. The Japanese spider crab is an omnivore, consuming both plant-matter and animals. It also sometimes acts as a scavenger, consuming dead animals. Some have been known to scrape the ocean floor for plants and algae, while others pry open the shells of mollusks. Taxonomic history The Japanese spider crab was originally described by Western science in 1836 by Coenraad Jacob Temminck under the name Maja kaempferi, based on material from Philipp Franz von Siebold collected near the artificial island Dejima. The specific epithet commemorates Engelbert Kaempfer, a German naturalist who lived in Japan from 1690 to 1692 and wrote about the country's natural history. It was moved to the genus Inachus by Wilhem de Haan in 1839, but placed in a new subgenus, Macrocheira. That subgenus was raised to the rank of genus in 1886 by Edward J. Miers. Placed in the family Inachidae, M. kaempferi does not fit cleanly into that group, and it may be necessary to erect a new family just for the genus Macrocheira. Four species of the genus Macrocheira are known from fossils: Macrocheira sp. – Pliocene Takanabe Formation, Japan M. ginzanensis – Miocene Ginzan Formation, Japan M. yabei – Miocene Yonekawa Formation, Japan M. teglandi – Oligocene, east of Twin River, Washington, United States However, some evidence indicates that the genus Macrocheira does come from this family in some way due to its anatomical arrangements. This genus is similar in anatomical arrangement to the genus Oncinopus, seeming to preserve the earliest stage of anatomical evolution in the family Inachidae. The genus Onicinopus has a semihardened body, which allows the basal segment of the antennae, which articulates with the head capsule, to move. The antennulae which are segmented appendages between and below the eye stalks are connected