For this hatch model to work however, the developing embryos must first develop eyespots before the eye index can be measured and subsequent hatch date predicted. Presently, this model is used for temperate species, where the time between the initial development of eye spots and hatch can be protracted. For example, the eye spots of S.verreauxi can be measured up to 60 days prior to hatch when eggs are incubated at 13 °C which gives significant notice of the impending hatch for management purposes (Moss et al., 2004).
Tropical species have comparatively more rapid egg development. Adult female P. ornatus have an incubation period of approximately three weeks before the developed larvae hatch when held at ambient summer temperatures ( Jones et al., 2003). Eye spots do not develop until around 12 days prior to hatch, giving only short notice of the impending hatch date and insufficient time for hatchery preparation (Jones et al., 2003)