Impact of feeding by Leptoglossus occidentalis (Hemiptera : Coreidae) on the major storage reserves of mature Douglas-fir (Pinaceae) seeds

In laboratory experiments adults and nymphs of the western conifer seed bug , Leptoglossus occidentalis Heidemann, were allowed to feed on mature seeds of Douglas-fir, Pseudotsuga menziesii (Mirbel) France. Weight-loss measure ments and scanning electron microscopy provided strong supporting evidence for the use of simple radiographic diagnosis as a method of classifying fee ding damage to seeds into four categories: Light (greater than two thirds o f seed contents remaining), moderate (one third to two thirds of seed conte nts remaining), severe (less than one third of seed contents remaining), an d extreme (seed empty). Scanning electron micrographs showed the apparent d epletion of lipid and protein storage reserves which was verified by quanti tative analyses that showed significant loss of lipid and buffer-insoluble (crystalloid) storage protein from seeds in all damage categories. The amou nt of buffer-soluble (matrix) protein was reduced in seeds from the severe and extreme damage categories. The increase in buffer-soluble protein obser ved in lightly damaged seeds was likely due to the solubilization of crysta lloid storage protein, as a result of its breakdown into smaller peptides. Our results suggest that through the action of both lipases and proteases, L. occidentalis can have a serious impact on the major storage reserves of conifer seeds. Moreover, our data suggest that L. occidentalis feeds in a d ifferent manner than the laceration and flushing method found in other seed -feeding Hemiptera.