The Development of the Species of Upogebia from Plymouth Sound

Abstract

Upogebia deltura Leach and Upogebia stellata (Mont.) are both of common occurrence on the coasts of Devonshire and Cornwall, but in the adult stage they are not easily obtained, owing to their burrowing habits. The larvæ, however, are very common in the tow-nets, occurring throughout the year with the exception of the midwinter months, and are particularly plentiful from June to August. The two species are closely allied, and for some time it was believed that the differences between them might be merely sexual, and not specific (Bell 1853). They are now clearly recognised as separate and distinct species, and De Morgan (1910) has obtained males and females of both forms. Upogebia deltura Leach may be distinguished by its greater size, sometimes five or six inches in length when full-grown, as well as by its broad abdomen with soft abdominal pleura. The two joints of the chela on the first thoracic leg are almost equal in length. Upogebia stellata (Mont.) is an altogether smaller and more slender animal, seldom exceeding two and a half inches in length. The abdomen is narrower, and the fixed finger of the chela very much shorter than the dactylus. There is also a small point on the side of the carapace, just over the base of the second antenna, which has been established as a specific character by De Morgan (1910). In the living state the body of the animal is covered with orange-red spots (hence its name stellata), while Upogebia deltura Leach is of a uniform dirty cream colour.