Probable RNA-dependent helicase. Functions in cell growth and proliferation. May have a role in ribosome biogenesis and, consequently, in protein biosynthesis. ATP + H2O = ADP + H(+) + phosphate Mutation in the pit gene produce larvae that cannot grow beyond the first instar larval stage although they can live as long as 7-10 days. All the tissues are equally affected and the perfectly shaped larvae are indistinguishable from first instar wild-type animals. 'Pitchoune' means 'small' in Provence (Southern part of France). Belongs to the DEAD box helicase family. DDX18/HAS1 subfamily.