They can’t be seen in a silver mirror which indicates their reflected light wavelengths go from 400 NM and below. Humans can see from to 380 NM to 700 NM . So, Clearly what kills them is their inability to discharge the visible light wavelengths energy fast enough, they overheat and then turn to dust as shown in Blade/JJBA/Underworld/Buffy/whatever
They can’t be seen in a silver mirror which indicates their reflected light wavelengths go from 400 NM and below. Humans can see from to 380 NM to 700 NM . So, Clearly what kills them is their inability to discharge the visible light wavelengths energy fast enough, they overheat and then turn to dust as shown in Blade/JJBA/Underworld/Buffy/whatever