The pinewood nematode (Bursaphelenchus xylophilus) is known to be the causative agent of pine wilt disease, which is transmitted from wilt-killed to healthy pine trees by the insect vector Monochamus alternatus. The second-stage propagative juvenile develops into third-stage dispersal (J_III) or propagative juveniles. The J_III develops into the fourth-stage dispersal juvenile (J_IV), a special stage for transportation, then the J_IV enters the tracheal system of adult beetles in pupal chambers in the xylem. To determine the differences in some life history parameters related to transmission between a virulent and an avirulent isolate of B. xylophilus, progression to the different life stages was investigated using two nematode isolates of different virulence, M. alternatus larvae, and pine bolts with an artificial pupal chamber. The numbers of J_IIIs and J_IVs produced around the pupal chamber by the time of beetle emergence were much smaller in the avirulent isolate than in the virulent one. The proportion of J_IIIs produced in a population around the pupal chamber (the J_III and J_IV number/the total population) and the probability of J_IIIs developing into J_IVs (the J_IV number/the J_III and J_IV number) were also smaller in the avirulent isolate. Although the probability of J_IVs boarding beetles (the initial nematode load/the J_IV number) was equal between the two isolates, the mean initial nematode load was much smaller in the avirulent isolate. The smaller initial nematode load of the avirulent isolate was ascribed to its smaller rate of reproduction and to lower production rates of J_III and J_IV. A trade-off between the virulence and transmission rate of B. xylophilus is discussed herein, taking into account the effect of the initial nematode load on the vector’s longevity and flight performance.

To evaluate the relationship between reproductive potential and body size of Dastarcus helophoroides Faimaire (synonym Dastarcus longulus Sharp), 17 adult females obtained under outdoor conditions were dissected individually to count the ovarioles and determine the mean size of mature eggs in ovarioles and oviducts following the measurements of fresh body weight, body length, maximum body width, maximum width of prothorax, and elytral length. Each female had two ovaries. The number of ovarioles per female varied from 36 to 154 depending on maternal body length. However, the mean length and width of mature eggs were independent of body length. There were no differences in any body-size traits and allometry between the sexes.

Bursaphelenchus mucronatus Mamiya et Enda has been recovered for the first time from adults of the cerambycid beetle, Monochamus urussovi (Fischer), in Hokkaido, Japan. The nematode was also recovered from the inner bark of Picea jezoensis (Siebold et Zuccarini) Carrière and Abies sachalinensis (Fr Schmidt) Masters infested with M. urussovi larvae. PCR–RFLP analysis indicated that B. mucronatus in Hokkaido is the European type.