A method is described for using near-infrared reflectance spectroscopy (NIRS) to quantify the amount of blood present in mosquitoes without killing insect. NIRS is a nonconsumptive, instrumental method for fast, accurate, and precise evaluation of chemical composition of material with little or no preparation. The NIRS method accurately predicted bloodmeal size and bloodmeal disappearance in Aedes aegypti (L.) and Ae. sierrensis (Ludlow) mosquitoes.