Differentiation of food habit in tree-boring insects and its ecological and evolutional significance

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The major results are summarized as follows.1. Some biological features such as emergence trend, longevity and attack pattern of wood borers, which were found in their host trees, felled bloadleaved-trees inculuding Acer spp., were examined for the project term. The features were compared among collection sites, Iwate, Fukui, Aichi, Mie and Shimane.2. Dissection of emerging adults of a xiphydriid woodwasp, Xiphydria ogasawarai, revealed that females possessed a new type of mycangia filled with fungal spores and produced a slime-like secretion in mucus reservoir (Kajimura 2000). The mycangial fungi were isolated and incubated on culture media.3. Seed-insect fauna of pre-dispersal acorns and seasonal patterns of acorn fall (Fukumoto and Kajimura 1999) and attack patterns of the insects on the acorns, in particular emergence periods of major species (Fukumoto and Kajimura 1999, in Japanese), were investigated in a mixed stand of Quercus variabilis and Q.serrata. Oviposition (boring) perio … More ds of the insects were clarified by using an original method in the stand, and interspecific competition between acorn-feeding guilds according to the periods was discussed (Fukumoto and Kajimura 2001).Fluctuation patterns of acorn production and insect infestation were detected by analysis of inner conditions in the acorns that fell into seed traps for four years (Fukumoto and Kajimura 2000, in Japanese). Rates of hypocotyl and radicle survival and of germination success were examined in relation to endosperm loss due to the insects (Fukumoto and Kajimura 2000).4. In some species of ambrosia beetles, isolations of fungi were made from walls of galleries in the host trees and mycangia of beetle adults. The isolated fungi were cultured under different conditions of temperature and humidity. Based on results of these experiments, a semi-artificial diet for rearing of the beetles was established, and a simple method for determining growth periods of their offsprings was also developed (Mizuno and Kajimura 2000, in Japanese). By the method, effects of temperature on the offspring growth were clarified. Degrees of dependence of the beetles on the isolated fungi were evaluated from view points of survival rate and other fitness compornents by artificial rearing experiments, which gave a notable result suggesting that primary ambrosia fungi associated with one beetle species are potential food for larvae of other species (Kajimura 1998). All the results and informations about ambrosia beetles, some of which were obtained in the 6th European Congress of Entomology, were summaried and reviewed, and further works were also proposed (Kajimura 1998, in Japanese ; Kajimura 2000, in Japanese). Less