Chemical forms of Se found in herbivore insects, and frass obtained from least squares linear combination fitting of each samples XANES spectra in comparison to standard selenium compounds.

XANES spectra were obtained from organisms at locations shown in Figures 4 and 5. SeO42−: selenate SeO32−: selenite; Se(GSH)2: seleno-diglutathione; C-Se-C: methyl-selenocysteine, seleno-methionine or seleno-cystathionine. SS: normal sum of squares (quality of fit; 0 = perfect); nd: compound not detectable.No elemental Se0 was found in these samples. Note: fractions do not always add up to exactly 100% because the margin of error can be up to10%.