Eucalyptus oils in larvae of gum emperor moth,Antheraea eucalypti

The ether-soluble portion of the foregut fluid from the larvae ofAntheraea eucalypti (Saturniidae) was found to contain traces (0.1-0.2%) of isoprenoids. The isoprenoids were those that were major components of the oils from the leaves of theEucalyptus species on which the larvae fed and were also soluble in the foregut fluid. This observation demonstrated that these larvae did not sequester the leaf oils in their foregut or use them for defense. The compositions of the oils, which were steam-distilled from the bodies and feces of the larvae, were identical with those of the oils from the leaves of the host trees. This fact implied that the volatile components of the leaf oils had not been metabolized and had no effect on the growth or feeding of the larvae, at least on the twoEucalyptus species examined. In order to explain the coevolution ofA. eucalypti andEucalyptus species, components of the leaf oils were suggested to serve the function of an ovipositional attractant to the female moths.