Upon heat shock causes cell death throughout embryos, though to a lesser degree than rpr^hs.PW. This cell death can be also be induced in a Df(3L)H99 background. A single heat pulse at a variety of stages is sufficient to kill flies, though late embryos and late pupae (where the rate of cell division is low) are more resistant to this lethality than other stages. 4-6 hours after a 1 hour heat shock at 39^oC, half the flies carrying the heat inducible rpr died, suddenly.