INTER-SPECIFIC DIFFERENCE IN BUDBURST TIME AND ITS CONSEQUENCES ON EGG HATCH TIME AND SURVIVAL OF THE GALL-MAKING ADELGID ADELGES JAPONICUS(MONZEN) (HOM., ADELGIDAE)

Temporal variation in budburst time of a host plant is important in de termining the performance of gall formers. To elucidate whether synchr ony of budburst and egg hatch affects the performance of gall-forming adelgids, the phenology of gallicola egg hatch and its survival were e xamined in Adelges japonicus (Monzen) on three plants (Picea jezoensis var, jezoensis (Sieb. et Zucc.) Carr., Picea jezoensis var. hondoensi s (Mayr) Rehder and Picea sitchensis (Bongard) Carr.) that differed in budburst time. Picea j. jezoensis is native, while P. j. hondoensis a nd P. sitchensis are introduced plants. Although the date of budburst differed significantly among these plants, neither the date of oviposi tion nor the date of egg hatch differed significantly among them; most of the eggs hatched after budburst in P. j. jezoensis, while a large portion of eggs hatched before budburst and larval gallicolae waited f or the buds to open in P. sitchensis and P. j. hondoensis. To examine the effect of this asynchrony on gallicola survival, the delay of egg mass disappearance with respect to budburst was correlated with the nu mber of gallicolae that colonized each gall. The correlation was signi ficantly positive in P. sitchensis but not significant in P. j. jezoen sis. This indicates that in P. sitchensis, gallicola survival decrease s with the increasing number of eggs that hatch before budburst, while budburst phenology does not affect gallicola survival in P. j. jezoen sis, which is their native host. However, when the number of gallicola e that colonized each gall was compared among the three plants, it did not differ significantly among them. This suggests that lower gallico la survival caused by a greater asynchrony of budburst and egg hatch m ight be compensated for by other factors (e.g. higher fecundity) that increase the number of gallicolae in the galls.