Movement of Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae) in tracheal system of adult Monochamus alternatus (Coleoptera: Cerambycidae)

To clarify the movement of Bursaphelenchus xylophilus in the tracheal system of adult Monochamus alternatus, 49 adult beetles were dissected 0, 15, 30, 45 or 60 days after emergence and the nematodes heading inwards to the distal end and outwards to spiracles in tracheae were counted. In adult beetles just after emergence, the majority of nematodes headed inwards. The proportion of tracheae with nematodes heading outwards was significantly higher for beetles aged 15, 30 or 45 days than for newly-emerged beetles. The proportion of nematodes pointing outwards tended to increase with beetle age and was significantly greater in 45-day old beetles than in newly emerged ones. A comparison of prediction with observation suggests that the nematodes move forwards in the tracheal system from spiracles and exit from spiracles after turning round in the tracheae.