Effect of Silhouette Color on Trap Catches of Dendroctonus frontalis (Coleoptera: Scolytidae)

With the exception of responses to semiochemicals, host selection behaviors of D. frontalis</it> are largely unstudied. To better understand the host finding behavior of D. frontalis</it>, and to identify potential visual disruptants, we evaluated the response of D. frontalis</it> to multiple-funnel traps of eight different colors. Multiple-funnel traps provide an attractive vertical silhouette, similar to a host stem, that aids in capturing bark beetles and allows for controlled evaluation of visual cues. Evaluation of mean trap catch of each color by analysis of variance (ANOVA) produced two separate groups: white and yellow traps caught significantly fewer D. frontalis</it> than the other six colors tested (black, blue, brown, gray, green, red). Examination of spectral reflectance curves showed that the eight colors could be naturally placed into two groups, those with high peak reflectance (white and yellow) and those with low peak reflectance (black, blue, brown, gray, green, red). When high and low peak reflectance were substituted for color in a separate ANOVA, reflectance group was as good as color at explaining the variability in trap catch (r</it>2 = 0.88 versus 0.92). Therefore, hue (dominant wavelength) was unimportant in affecting D. frontalis</it> host finding behavior at the reflectance levels we tested and, thus, we found no strong evidence that differential wavelength sensitivity affected the response of D. frontalis</it>. These results show that dark colored silhouettes (those with low reflectance values), regardless of hue, are best for capturing D. frontalis</it>, while white or yellow are the best candidate colors for disrupting host finding.