Adult Platypus quercivorus beetles were artificially inoculated into Japanese oak trees (Quercus crispula). Two inoculation methods were used: uniform inoculation through pipette tips, and random inoculation by release into netting. Four of the five trees that were inoculated uniformly died, as did all five trees that were inoculated at random. Seven of the nine dead trees showed the same wilting symptoms seen in the current mass mortality of oak trees. Raffaelea quercivora, which has been confirmed to be the pathogenic fungus that causes wilt disease and is usually isolated from the mycangia of P. quercivorus, was isolated from all of the inoculated dying trees. Trees that died faster showed a higher density of beetle galleries that succeeded in producing offspring. We found positive relationships between the density of beetle galleries that succeeded in producing offspring and the rate of discoloration in the sapwood and the isolation rate of R. quercivora. Therefore, we clearly demonstrated that P. quercivorus is a vector of R. quercivora, and that the mass mortality of Japanese oak trees is caused by mass attacks of P. quercivorus.

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The oak platypodid beetle, Platypus quercivorus, stridulates both during premating behavior and when stressed, as well as spontaneously. When a female was put onto the bark surface of a male-infested log, she began to walk and produce an "approaching chirp," searching for a gallery entrance. When finding one, she entered it and tried to pull a male out. If the male's abdomen became visible, she appeared to push her frons against his elytral declivity and made a "premating buzz" that lasted about 5-10 s. During this buzzing, the male backed out of the gallery in order to allow her in. Females that had been silenced via surgery did not evoke this reaction; thus, males apparently identified females by their buzzing sound. The male then followed the female into the gallery, and produced an "in-gallery chirp" with his posterior abdomen visible. After a while, both sexes backed out of the hole and copulated at the entrance. Both sexes produced "stress chirps" when confined inside a cotton ball, and "spontaneous chirps" when walking alone on the surface of an oak bark piece.

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Changes in Stand Structure after the Mass Mortality ofOak Trees in Keihoku Area, Kyoto City, Japan. J. Jpn. For. Soc. 91: 15 20. The effect of mass mortality of oak trees, caused by the fungus Raffaelea quercivora, on the stand structure of a broadleaved secondary forest was investigated in a stand located in northern Kyoto City, in mid-western Japan. In the study stand after the epidemic, Ilex pedunculosa was the dominant species basal area , followed by Fagus japonica, Quercus crispula, Acanthopanax sciadophylloides, and Magnolia salicifolia. More than half the Q. crispula individuals died during the epidemic. The number of dead Q. crispula trees suggested that the species would have been dominant in the tree layer before the epidemic. Individuals closer to the epidemic source and larger individuals suffered the highest mortality. M. salicifolia, A. sciadophylloides, and F. japonica had many stems expected to regenerate in the gaps resulting from death of Q. crispula trees, and these species are predicted to become more dominant in the tree layer at least in the short term. Hamamelis japonica var. obtusata and I. pedunculosa are also predicted to become more dominant in the middle and shrub layers.