Flies homozygous for the mutant chromosome Patj[synnull], which carries the genomic rescue fragment Cdc37^{+t9.5.Δdpatj} (lacking the coding region of Patj), in combination with α-Spec^Ubi-p63E.PP and dlt^Ubi-p63E.PP recombined onto a Df(3L)MY10 mutant chromosome, die during second instar larval development. Flies heterozygous for Patj[synnull] in combination with Df(3L)MY10 are also second instar larval lethal. Patj[synnull] mutant clones show severe disruptions in rhabdomere development and partial or complete loss of photoreceptor in ommatidia.