Respiratory gas exchange was measured in various developmental stages of the flea Xenopsylla conformis mycerini (Rothschild, 1904) originating from the central Negev in Israel. Gas exchange in fleas was measured using a flow-through respirometry system that monitored CO2 emission. Lowest metabolic rates were found in the cocooned stage, which included prepupae, early stage pupae, late stage pupae, and preemerged adults. Newly emerged adults and feeding larvae had metabolic rates 2.5-3.0 times greater than those for the cocooned stages. Highest rates of gas exchange were found in feeding fleas. The low metabolic rates of the cocooned stages is thought to contribute to their ability to survive for longer periods than free-living larvae and adults.