By E. Shipp, University of New South Wales
Synopsis.
Egg samples were obtained from populations of Didymuria violescens at Mt. Warning (near the coast at the border of New South Wales and Queensland), Jenolan (Central Highlands, N.S.W.) and Kiewa (Highlands, north-east Victoria). The eggs were maintained as follows: (a) under three sets of temperature conditions, having both diurnal and seasonal variations, with periodic moistening; (b) as for (a) but without moistening; and (c) under constant temperature conditions.
Under the influence of the varying temperature conditions the Mt. Warning eggs hatched during the first spring after oviposition, while of both Kiewa and Jenolan eggs the majority hatched during the second spring. The course of egg development may vary between two extremes, one without any noticeable interruption of morphogenesis and hatching, other than that caused by temperatures below the threshold of development (Mt. Warning), and the other generally with two firm and separate diapause states (Kiewa).
Rates of development and hatching of eggs with no added moisture were similar to those of eggs maintained under the same temperature conditions but with periodic addition of water.
Under constant temperature conditions Kiewa eggs conipleted pre-embryonic
diapause over the whole range tested, i.e. 40° F. to 70°
F. Morphogenetic development was completed at 60° F. and 70° F.,
while at 55° F. it proceeded more slowly, As indicated by hatching,
post-embryonic diapause was completed in about 30% of eggs held at 60°
F. and a few of those at 55° F. but not at other temperatures.