Potential feeding deterrents found in hemlock woolly adelgid, Adelges tsugae

The nonnative hemlock woolly adelgid (Adelges tsugae Annand, Hemiptera: Sternorrhyncha: Adelgidae) has been a significant mortality agent of eastern hemlock (Tsuga canadensis Carriere) throughout a large portion of its geographic range. During a study investigating adelgid vigor in relation to host health, it was noted that adelgid extracts ranged from a yellow to a deep red color. Analysis by GC-MS identified the presence of the anthraquinone, chrysophanol and its anthrone precursor, chrysarobin in the extract. These compounds are predator deterrents in several other insects, including chrysomelid beetles. It is hypothesized that these compounds serve a similar purpose in the hemlock woolly adelgid.