Effects of low-temperature summer nights on adults of Monochamus alternatus (Coleoptera: Cerambycidae)

Abstract

ABSTRACTTo clarify the factors determining the northern distribution limit of Monochamus alternatus Hope, which vectors the pinewood nematode, we examined our hypothesis that “low-temperature summer nights in cool regions affect the survival, maturation feeding, and ovary development of M. alternatus, and determine its distribution limit.” We measured summer air temperatures in three pine forest stands in northern Japan. Based on the results, we examined the effects of low nighttime temperatures on survival, maturation feeding, and ovary development in the laboratory. Low nighttime temperatures had little effect on the survival and the total amount of maturation feeding of M. alternatus adults. A daytime temperature of 25°C and nighttime temperature of 15°C did not affect ovary development. In contrast, 25°C in the daytime and 10°C in the nighttime delayed ovary development and reduced the number of mature eggs, but some ovary eggs were able to mature under this condition. We concluded that the effect of low-temperature summer nights on ovary development alone could not explain the northern distribution limit of M. alternatus.