Odonatological Abstracts

(538) DEGRANGE, C., 1971. L’oeuf de Hemianax ephippiger (Burmeister) 1839 (Odonata, Anisoptera, Aeschnidae). Trav. Lab. Hydrobiol., Grenoble 62: 131-145. – (Lab. Zool, Univ. Grenoble, Domaine Universitaire, F38 Saint-Martin-d’Hères). Oviposition was studied in adult 99 kept in captivity during several weeks. If their wings are arrested, they can survive for over 80 days, depositing about 1600 eggs during this period. The egg membranes (chorion, vitelline membrane) were studied with the electron microscope as well as in histological sections. A description is given of the micropylar system. At the anterior pole of the egg the endochorionic membrane is thickened under the hemispheric outgrowth of the exochorion. This structure is compared to the situation in the representatives of the genera Anax and Aeshna. Hemianax appears intermediary between the two. The Aeshna egg is considered to represent a primitive type. (539) HYNES, H.B.N., 1971. Zonation of the invertebrate fauna in a West Indian stream. Hydrobiologia 38 (1): 1-8. – (Dept. Biol, Univ. Waterloo, Waterloo, N2L : 3GI, Ont., CA). Samples of the invertebrate fauna collected at 10 points on a mountain stream in Trinidad reveal that the fauna is altitudinally zoned and that the apparent boundary between rhithron and potamon is below 30 m. This is very much lower than has previously been reported in the tropics. The samples included large numbers of specimens of the odon. genera Argia, Hetaerina and Brechmorrhoga.