Heteroallelic combinations of hat alleles exhibit a late pupal effective lethal phase. Many mutants only partially eclose, the operculum opens adn the heads and thoraces emerge. Individuals are unable to complete eclosion as their legs are enmeshed in undegraded pupal cuticle.
Pharate adults appear morphologically normal, but only partially eclose. Heads and thoraxes may emerge, but fail to complete emergence.
Denell.