FlyBase curator comment: this entry is used to capture phenotypic information when the particular allele (or allele combination) used by the author could not be determined but the context of the experiment suggests that the phenotype being described is some kind of loss of function.
Mutant flies have weak behavioural rhythms under constant darkness conditions and only 45% of the animals are rhythmic. The behavioural period of the rhythmic flies is indistinguishable from wild type. The mutant flies show a sleep phenotype under constant darkness that is similar to that observed in the mutant flies under light-dark cycles.