Infrared spectral sensitivity of Melanophila acuminata

The spectral sensitivity of the pit organ of the beetle Melanophila acuminata (Coleoptera:Buprestidae) was measured using an ultrafast tunable infrared laser source and standard electrophysiological techniques. The pit organ may be classified as a broadband detector as the beetles responded to all infrared excitation wavelengths from 2 to 6 μm. There was a decrease in response threshold and latency and an increase in the magnitude of the response in the region from 2.8 to 3.5 μm, which corresponded to a region of decreased transmittance (increased absorbance) as measured by Fourier transform infrared spectroscopy. The implications of the correlation between spectral response and optical properties are discussed.