Volicitin [N-(17-hydroxylinolenoyl)-L-glutamine] was identified from the regurgitant of Spodoptera exigua, as an elicitor of corn volatile emissions. Volicitin and analogs (FAAs) have not only negative consequences for the insect itself, but also might play an important physiological role in the caterpillar’s metabolism. ¹⁵N-NMR and several trace experiments with ¹⁵N-labeled compounds suggested that the combination of biosynthesis and degradation of FAAs enhanced nitrogen assimilation and recycling in S. litura caterpillars. The glutamine conjugates are thought to be the primary FAAs, common to all the Lepidopteran species reported to have FAAs. Also the glutamine moiety was shown to be crucial for corn volatile induction. Screening for FAAs in wild Lepidopteran species showed structural diversification with speciation, mostly resulting in loss or decrease in elicitor activity on corn seedlings.