Substantial amounts of water are excreted by tsetse flies immediately after ingesting a blood meal and during subsequent digestion where faecal matter is voided as a semi-liquid paste, which also involves water loss. This document discusses quantifying the amounts of water lost through these two excretion processes to better understand the water balance of tsetse flies. It divides the investigation into two sections, one focusing on the preliminary water excretion right after feeding and another on the later voiding of faecal matter.