The sand fly Lutzomyia longipalpis (Lutz & Neiva) (Diptera: Psychodidae), is the vector of the Neotropical parasite Leishmania chagasi. Designing methods to control the spread of this pathogen involves maintaining large laboratory colonies of these flies. However, transmission studies have been hampered particularly in regard to significant fluctuations in colony productivity. In the process of optimizing our sand fly rearing protocol, we increased moisture levels in the environment of the adult blood-fed female and found that egg development increased, whereas sand fly longevity decreased. Interestingly, continuous moisture from the fourth day after a bloodmeal significantly increased the longevity of the fly, but it did not significantly decrease the number of eggs developed. These results will help guide investigators aiming to manipulate the longevity and productivity of sand fly colonies.