The effective lethal phase of homozygotes is during the late third instar stage and early pupation. 30% of homozygous larvae enter pupation but never reach adulthood. Larvae take almost twice as long to reach pupation as normal. The larval CNS shows aberrant and drastically reduced proliferation (as shown by 5-Bromodeoxyuridine labelling). MT:DNA cannot be detected in mutant larvae, indicating severe depletion compared to wild type. Oxygen consumption is reduced to approximately 10% of the wild-type level in mutant larval tissues. Mitochondria are present in larval tissues and for the most part show normal morphology and number; no changes at all are seen in the CNS, whereas there is an increase in mitochondria in the midgut, where some cells have a large number of aberrant mitochondria that appear to be in various stages of disintegration or engulfment by lysosomes.

Lethality acts in the prepupal and pupal stages.