Heat shocking females causes eggs produced to have reduced dorsal tissue and fusion of the dorsal appendages. Larvae hatch from the eggs, with dorsal-ventral pattern unperturbed. A small proportion of eggs 0.4%, with forked appendages appear even without heat shock. When the dose of spi is halved this proportion increases to 8.8%.

Used to analyse mutant phenotype of rho mutants in follicle cells. The eggs laid after heat shock during stage 8-10 of oogenesis (when rho is expressed in wild type) show ventralized eggshell phenotype. Eggs laid also show embryonic lethality, with those that secrete a cuticle being ventralized at the expense of dorsal structures, similar to grk and Egfr mutants. The large percentage of nonhatching embryos reflects failure of fertilization and ventralization of the embryo.