Physical Dynamics of the Noncleidoic Egg of Stephanitis pyrioides (Heteroptera: Tingidae) During Development

Abstract

Overwintering feral eggs of the immigrant azalea lace bug, Stephanitis pyrioides (Scott), and eggs laid on plants in a rearing chamber were sampled over time and measured for changes in size and weight during development. Eggs collected from both sources that were incubated in a rearing chamber were found to increase significantly in width and breadth. For eggs laid in the rearing chamber the greatest rate of change occurred between days 2 and 4 of embryo development, whereas in the feral eggs it occurred between Julian days 54 and 82. Although a cubic relationship was significant between day of embryo development and width and breadth for rearing chamber eggs, a quadratic relationship was significant between Julian day and width and breadth for feral eggs. Measured length of rearing chamber eggs did not change over time, but the length of feral eggs increased linearly with Julian day. An increase in weight of feral eggs was linearly related to Julian day and the mean weight of eggs laid in the rearing chamber was quadratically related to day of embryo development. Excised leaves with feral eggs were sampled biweekly during periods of dormancy and spring growth. It was determined that adequate moisture was present in the leaves for the embryo to complete development. Because number of days to preemergence was significantly influenced by Julian day (i.e, sampling date), the mean number of nymphs to emerge at each particular sampling day was not significantly influenced by moisture or day. The significant increase in egg width, breadth and weight indicates that the egg of S. pyrioides is noncleidoic and that the chorion is both pervious and elastic. A possible impact on voltinism is discussed.