Bark reflectance spectra of conifers and angiosperms: implications for host discrimination by coniferophagous bark and timber beetles

The spectral reflectance of phytophagous insects' host plants is usually quantified between 300–350 nm (ultraviolet, UV) and 700 nm (farred to infrared), and the shape and magnitude of the distribution of reflected light determine the hue, saturation, and intensity perceived by insects (Moericke 1969). Host perception also depends on the distribution of environmental light (Endler 1993) and on the constraints of the insects' visual system, which is usually described as dichromatic, with one type of photoreceptor responding maximally to blue light (λ max = ca . 400–470 nm) and another to green light (λ max = ca . 500–530 nm). UV receptors also appear to be common, if not ubiquitous (Briscoe and Chittka 2001; Mazza et al. 2002). Several phytophagous insects have been shown to use visual cues, including UV reflectance, to locate and (or) discriminate among plants (Prokopy and Owens 1983).