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In arid areas, Phlebotomus papatasi obtains essential carbohydrates by feeding on green tissues of plants. There is a great variation in sugar content, metabolic rates and dark respiration between conspecific plants, and also between branches and leaves of the same plant. It is hypothesized that high nocturnal release of CO2 may guide the sand flies to rich sugar sources. Comparisons of Ph. papatasi feeding on branches of different plant species demonstrate a significant positive correlation between the level of sugar in leaves, the rate of sand fly feeding on them and the size of ingested sugar meals. Mean nocturnal CO2 emanation of low-sugar Ricinus communis branches is 26.5 ppm and that of sugar rich branches is 86.3 ppm above room level. Low-sugar Capparis spinosa branches release 45.0 ppm and the emission from sugar rich branches is 76.0 ppm above room level. Branches with similar emissions, placed behind net partitions, are used in no-choice orientation experiments: R. communis branches releasing high CO2 levels are approached by 53.7% of the flies compared with 3.0% of flies that orientate to low CO2 branches. Capparis spinosa with high CO2 emission are approached by 9.8% of the flies compared with 0.95% of flies that orientate to low CO2 branches.