We used the first measurement, of cleavage-stage eggs at ~0.6 days, as an estimate of the initial size at laying, because perivitelline chamber expansion begins only after gastrulation (Pyburn, 1963), then measured eggs every 8 h until hatching. Clutches were maintained using an automatic misting system that sprayed rainwater for 30 s each hour. We initially measured eggs using an ocular micrometer under a dissecting microscope at ×32 magnification to ensure that we could see the vitelline membrane clearly.