Eriocheir ogasawaraensis Komai, a new species of mitten crab (Crustacea: Decapoda: Brachyura: Varunidae) from the Ogasawara Islands, Japan, with notes on the systematics of Eriocheir De Haan, 1835

A new mitten crab species of the genus Eriocheir De Haan, 1835, E. ogasawaraensis n. sp., is described from the Ogasawara Islands, Japan. It is morphologically most similar to E. japonica (De Haan, 1835), found on the Japanese mainland, the Ryukyu Islands, Taiwan, the Russian Far East, Korea and China, but diagnostic is the proportionately broader and dorsally flattened carapace which usually lacks the fourth anterolateral tooth, the ornamentation of the epistome, the male first gonopod and its the coloration. The biology of the new species and the different interpretations concerning the systematics of Eriocheir are briefly discussed.

Interference between "Sex-Ratio" Agents of Drosophila willistoni and Drosophila nebulosa

Interference between two "sex-ratio" agents-that is, treponemalike spirochetes-of different origin, one from Drosophila willistoni and the other from D. nebulosa, was demonstrated by experiments in vivo and in vitro. When the two sex-ratio agents were combined in females of the Oregon-R strain of D. melanogaster, expression of the sex-ratio condition was temporarily interrupted. Several lines of evidence indicate that a substance produced by the sex-ratio agent of D. nebulosa may kill or incapacitate the sex-ratio agent of D. willistoni.