The Absorption of Water and the Associated Volume Changes Occurring in the Eggs ofNotostira ErraticaL. (Hemiptera, Capsidae) During Embryonic Development Under Experimental Conditions

The eggs of Notostira erratica L. (Hemiptera) swell during embryonic development. Increase in wet weight accompanies swelling. Under the conditions of the experiments described in this paper the gross increase in wet weight of the eggs from oviposition till hatching is due entirely to the increase in amount of water. The weight of water per egg is, however, slightly greater than the increase in wet weight of the same egg, since the amount of dry matter per egg decreases slightly during development. The increased amount of water must be largely due to absorption from the external environment: a certain amount, however, is probably metabolic water, which if due to oxidation of fat in the yolk would result in an increase in wet weight of the egg. This increase due to metabolic water will tend to be balanced by the decrease in dry matter during embryonic development. The increase in volume of an egg during embryonic development is directly proportional to its increase in wet weight during the same period. Theoretically it would be more accurate to correlate volume change with the amount of water in the egg; this cannot be done accurately enough, however, with the present methods. The embryonic development and the extrusion of the subopercular yolk-plug in relation to water absorption are briefly described. The work of other authors concerned with water-absorbing insect eggs is discussed. The method used for finding the volume of the eggs (which does not involve their death) is described in detail.