Color variation in ectotherms is influenced by selection for multiple functions including thermal benefits. Thermal effects depend on the integument reflectivity across the full spectrum of sunlight, including ultraviolet (UV), visible (VIS), and near infrared (NIR); but the latter is rarely considered. Here, we examined the relative contribution of UV-VIS and NIR reflectivity to radiative heat gain for 17 species of jewel beetles (Buprestidae) that vary in the reflectivity of the elytra. We measured the heating rate of the elytra using a solar simulator and a thermal chamber to control the effect of conduction and convection, and optical filters to isolate the effect of UV-VIS and NIR reflectivity. We also investigated the effect of other cuticle properties, namely surface area, thickness, and surface rugosity. We found that reflectivity predicted heating rate and this was driven by the variation in NIR rather than UV-VIS reflectivity. Surface area had a weak effect on heating rate, whereas cuticle thickness and surface rugosity had no detectable effect. Heating rate of isolated elytra corresponds to differences between species in heating rate of whole beetles measured with the same method. Taken together, our results suggest that the reflectivity of elytra has an important effect on radiative heat gain in jewel beetles and highlights the potential role of NIR reflectivity in thermoregulation. NIR reflectivity may be particularly important for thermoregulation because it is free from selection for visual functions such as camouflage or communication.