Larvae transheterozygous for Nup154² and either Nup154⁰¹⁵⁰¹ or Nup154^k08204 die throughout the early larval stages, with survivors found until only just after the third instar larval moult. Until the end of the second instar stage, the larvae appear morphologically similar to their heterozygous siblings in body and tissue size. After the third instar moult, the larvae fail to grow and show a "classic mitotic mutant" phenotype, including reduced overall body size and a reduction in the size of larval organs that normally contain proliferating cells. Homozygous, hemizygous or transheterozygous third instar larvae have smaller brains than their age-matched control siblings. Although the neuropil is relatively normal in size, the optic lobes are greatly reduced and imaginal discs are tiny and difficult if not impossible to locate. The lymph glands are also reduced in size in third instar larvae. Homozygous second instar larvae have a normal number of circulating haemocytes in their haemolymph. However, by the third instar stage they show a drastic reduction in haemocyte number compared to their age-matched control siblings. Testes of third instar larvae are also abnormally small and contain only a few germ cells resembling primary spermatocytes.