Nestmate identity and foraging area of Syntermes spp. (Blattodea: Termitidae) using near-infrared spectroscopy

Abstract

Subterranean termites of the genus Syntermes are important early pests in eucalyptus culture. The amount of damage caused by these termites may be related to the size of the colony and its foraging area. To determine this, one can use the Near Infrared Spectroscopy (NIR) technique, which is able to detect chemical composition variations of insect cuticle hydrocarbons and discriminate species and siblings. In the first study, the NIR and the partial least squares discriminant analysis (PLS-DA) were used to identify the colonial origin of the termite Syntermesgrandis, which has superficial nests. The accuracy was of 98% in the identification of nests using workers and soldiers of this species. The method was important for the qualitative characterization of the colonial phenotypic response of this species. In the second study, we tried to use the same technology to determine the correspondence between the foraging holes of Syntermesnanus, which has subterranean nests. The spectral measurement of termites resulted in 424 spectra, a mean spectrum for each worker analyzed, correspond to 52 different holes collected, in each hole were collected numbers of workers ranging from 8 to 23 workers. The spectra most correlated to each other by principal component analysis (PCA) among the 1556 wavelengths collected were the ten spectra in the range of 7020.89648 cm -1 to 7055.1655 cm -1, each 3.85764 cm -1, which coincides with the highest absorbance values found. The NIR technique did not allow the separation of termite colonies Syntermesnanus, as was done for Syntermesgrandis, making it impossible to determine the foraging area of this species.