Copyright © 2011 by The American Society of Tropical Medicine and Hygiene

Mosquito age grading, or the ability to determine age, is important in vector control programs. Because of the extrin-sic incubation period of the parasites and pathogens that mos-quitoes transmit, only older mosquitoes are potential vectors of mosquito-borne diseases. Indeed, novel control strategies envision a shift in population structure toward younger mos-quitoes, thereby reducing the number of disease-transmitting individuals in the mosquito population. 1, 2 A wide variety of techniques has been used for age grading in mosquitoes. These include changes in ovarian morphology, 3 cuticular hydrocar-bons, 4 pteridine concentrations, 5 and gene transcription. 6, 7 Recently, near infrared spectroscopy (NIRS), which quantita-tively measures organic compounds, e.g., O–H, N–H, and C–H functional groups, has been used for mosquito species iden-tification and age grading. This method is non-invasive and was initially performed on fresh specimens from laboratory colonies or mosquitoes reared under semi-field conditions. 8, 9 However, the use of fresh specimens under field conditions might be impractical. The preservative RNA later (Ambion, Austin, Texas) has been used to store mosquitoes for NIRS age grading and species identification, 10 but this is an expen-sive storage medium. Here, we compare the effect of various lower cost storage methods commonly used for insects on our ability to predict mosquito age using NIRS. Anopheles gambiae s.s. mosquitoes (G3 strain) were reare