Contrary to most other Diptera, the inter-rhabdomeral spaces of the retina of the Jamaican cavefly Neoditomya farri are filled neither by extracellular matrix nor dense cytoplasmic material. Instead, a foamy organization of loose vacuoles, measuring approximately 0.7 μm in diameter, appears to keep the rhabdomeres of retinula cells 7 and 8 in place. The vacuoles are bounded by membranes and traces of actin, determined immunocytochemically, are present. The origin of the vacuoles is unclear, but evidence in support of a retinula cell rather than cone cell origin is advanced.