Shining light on species delimitation: How spectrophotometry could unravel the Chrysobothris femorata species complex

The flatheaded borer, Chrysobothris femorata (Olivier), (Coleoptera: Buprestidae) is part of a species complex comprising 12 similar-looking species. This beetle has a wide host range and poses significant problems in commercial nurseries and urban landscapes, where it can cause the rapid decline of economically important trees. Adult beetles are "bullet-shaped" with large compound eyes. In most cases, identifying the species requires examining the male >genitalia, making species determination difficult without destructive sampling. Also, there are only handful of experts in the country to confirm the species identity. In this context, to provide a non-destructive method for species delimitation and to create a spectrophotometry database of these beetles, we spectrally measured the dorsal side, head + thorax, elytra, abdominal tip, ventral side, and ventral tip of the beetles. Using six samples and three replications for each species, we recorded L*, a*, and b* values and visible spectral readings from 360 to 740 nm for each body part. We performed Principal Component Analysis and Linear Discriminant Analysis and found significant spectral differentiation between species. Females of C. femorata and C. shawnee were clearly distinguished in our results. Additionally, C. femorata and C. sexignata (outgroup) adults emerging from the same host red maple plants could also be distinguished by spectral characteristics. We aim to improve the sample size in the future and to focus on the most informative body parts of the beetles to use spectrophotometry in delimitation of Chrysobothris femorata species complex.