Above left is a wild-type, 3rd instar larva. If it were still alive, it would be wandering around, looking for a nice place to pupate and go through metamorphosis.
The larva on the right is a mutant that lacks the DmBLM helicase and the MUS81-MMS4 nuclease. It would also be looking to pupate, unaware that it's going to die before becoming an adult. Note the dark spots inside the larvae. These are melanotic tumors, which result from an immune response to necrotic cell death. This phenotype was described in
K. Trowbridge, K.S. McKim, S.J. Brill, and J. Sekelsky (2007) Synthetic lethality of Drosophila in the absence of the MUS81 endonuclease and the DmBlm helicase is associated with elevated apoptosis. Genetics 176: 1993-2001.
S.L. Andersen, D.T. Bergstralh, K.P. Kohl, J.R. LaRocque, C.B. Moore, and J. Sekelsky (2009) Drosophila MUS312 and the vertebrate ortholog BTBD12 interact with DNA structure-specific endonucleases in DNA repair and recombination. Molecular Cell 35: 128-135.