Bacteriophagous Caenorhabditis japonica forms a phoretic and necromenic association with the burrower bug Parastrachia japonensis. C. japonica dauer larvae (DL) disembark from the body surface of P. japonensis females before their propagation in the nest of the carrier insect. In this study, we examined the conditions and possible cues for disembarkation. In high humidity conditions, not all the DL that were naturally associated with or artificially loaded on P. japonensis disembarked from their carriers. The presence of food bacteria or the soil habitat did not enhance disembarkation. However, the presence of P. japonensis nymphs promoted disembarkation. These results indicate that only some C. japonica DL leave their carriers under conditions of high humidity and that the presence of nymphs after hatching stimulates disembarkation. DL collected from P. japonensis females several months after eclosion showed gravitactic behavior while those from P. japonensis 3 days after loading did not, suggesting behavioral changes in DL during their association with the carrier.

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We examined the effects of vector cerambycid beetles, tribe Lamiini, on the formation of the phoretic stages of Bursaphelenchus conicaudatus and B. luxuriosae, using a new, simple nematode-loading method. Fourth-stage dis persal juveniles (JIV) of B. conicaudatus and a putative “entomoparasitic adult form”(PA) of B. luxuriosae are vectored by Psacothea hilaris and Acalolepta luxuriosa, respectively. Bursaphelenchus conicaudatus JIV and B. luxuriosae PA developed in the presence of their vector beetles, and were not recorded without those beetles. We concluded that the presence of vector beetles affected the life cycle strategy of B. conicaudatus and B. luxuriosae.

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Some quick and easy techniques for nematode morphological observations are provided. Silicone grease or petroleum jelly can be applied to adjust the nematode direction to observe lateral or ventral aspects. Small spots of the grease are placed between the slide glass and coverslip to fix the coverslip and adjust sample thickness. Nematodes can be turned by moving the coverslip, which can be pushed to observe the complicated stomatal morphology. Squashing of the nematode is handy to evert the buccal cavity. Furthermore, diluted detergents (0.1-0.5% Tween 20 or 80) can be used to remove bacterial particles stuck on the nematode surface and observe the surface structure of the nematode.

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