During development, remodeling of the larval nervous system is necessary for establishing adult specific behaviors in the fruit-fly Drosophila melanogaster. During metamorphosis, five pairs of abdominal nerves fuse together to form a terminal nerve trunk (TNT) as they exit the CNS. Segmental nerves defasciculate from the TNT at appropriate segmental levels to innervate the body wall. Glial cells are likely to play a significant role in nerve fusion and we are interested in examining layer specific remodeling of the nerve during metamorphosis. The most external layer, the non cellular layer of extracellular matrix called the neural lamella, disappears during the first quarter of pupal development and appears again during the last quarter of pupal development. However, the two glial layers- the perineural glia (PG) and the sub-perineural glia (SPG) persist during this process. The innermost layer-the wrapping glia retracts its processes during early pupal development and after the third day of metamorphosis, extends its processes. Glial cell numbers across all cellular glial layers change during pupal development. Confocal microscopy analyses have been substantiated by transmission electron microscopy (TEM) to study the ultrastructural changes that take place during peripheral nerve reorganization. The present study focuses on the role of the most external layer, the PG in TNT formation. A three-fold increase in the glial population was observed during the first day of metamorphosis (25% of development), when 75% of the cells comprises of perineural glia. Induction of perineural glial cell death by targeting the cell death gene reaper and the Diphtheria Toxin (DT), results in eclosion defects (28% emergence and 3% emergence respectively). TNT branching pattern was defective in 100% of the experimental animals analyzed at the pharate adult stage (n=15). TEM studies are currently underway to identify the nature of ultrastructural changes in these mutants. The study of glial remodeling in Drosophila will lay the groundwork for future studies on the role of glia- neuron communication during TNT formation, and could lead to the establishment of a model system to study gliopathies.