Skinner, Ernest B. (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XIV, Part I (1902)
Ten species of Arrenuri belonging to the subgenus Megalurus thon, pp. -Plate XVIII ff.
TEN SPECIES OF ARRENURI BELONGING TO THE SUBGENUS MEGALURUS THON. BY RUTH MARSHALL. The work upon the genus Arrenurus Duges has been carried on fron4 the spring of 1893 up to the present time, with many interruptions. Collections have been made at several places in Wisconsin and one in -Massachusetts. This paper embodies the results of the studies upon the species of the subgenus Mega- lurus Thon, most of the work having been centered on this group. The Arrenuri form one of the most easily recognizable genera of the Hydrachnidae. They form a, sharply defined, highly organized and well differentiated group, very rich in speies They are characterized by the possessession of a very hard, transparent, porous in gumentan area of -which ise--parated- on the back by a circular furrow from the rest to form the so-called "dorsal shield"; and by great sexual diamorphism. The females have a more or less rounded form and closely resemble each other; while the imiales have a peculiar prolonga- tion of the posterior end of the body, presenting numberless modifications in the different species and offering the chief spe- cific characters. Thon (1900) makes three subgenera of the Arrenuri. Petio- lurus -embraces species in which the posterior appendage is short, or altogether wanting and represented by humps on the dorsal side of the body; and in which there is a peculiar and characteristic structure, the "petiole," a small oblong chitinous structure at the extreme posterior end of the body. Arrenurue pustulator Muller is an illustration. Subgenus Micrurus has 10 - - -
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