The morphology of larval stages of Longidorus martini having been reported as a vector of mulberry ring spot virus was described for the first time. The larval body contour was similar to that of the adults except for a smaller body size. Three stages of the larval development were characterized by the measurements of length of odontostyle and of replacement odontostyle, and by the location of guide ring (distance from the anterior end). Those values (μm) in each stage were indicated as follows. 1st-stage larvae; 58 (55-63), 67 (63-70), and 27 (24-30), 2nd-stage larvae; 65 (62-77), 84 (72-93), and 38 (33-42), 3rd-stage larvae; 82 (75-90), 107 (97-113), and 48 (45-52). Mulberry seedlings in pots were inoculated with 100 hand-picked females at 20-25°C, and development of larvae was examined every 1 month intervals for 6 months. The results were that newly matured adults and the 1st-stage larvae of the second generation emerged 2 months and 5 months after inoculation, respectively. The length of a life cycle, from adult to adult, appeared shorter than 4 months. Number of the nematodes recovered 6 months after inoculation was about 4.5 times.

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Embryonic and post embryonic development of Bursaphelenchus lignicolus, the causal agent of wilting disease of pine trees, was studied. Eggs took 26-32 hr to hatch in water at 25°C. There were four molts, the first in egg. The second-stage larvae began to feed soon after hatching as they were placed on fungal mat. Feeding was necessary for further development. In fungal cultures of Botrytis cinerea hatched larvae reached adults in 4 days at 25°C, and oviposition took place on the 4th day after hatching. The measurements of body and gonad length made it possible to distinguish the various larval stages. L_III, regarded as third stage but different in morphology and biology from the usual third-stage (L₃), can be defined as the resting stage in the life cycle of B. lignicolus, and has its biological significance as the stage preceding the dispersal fourth-stage larvae which appear to be “Dauerlarven” in their morphological features. The life history in fungal cultures of B. cinerea was completed in 12 days at 15°C, in 6 days at 20°C, in 4-5 days at 25°C, and in 3 days at 30°C. At 33°C, the development was a little restrained. It was theoretically demonstrated that the minimum temperature for development was 9. 5°C. Copulation was necessary for reproduction.

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Presence of a pair of ventro-median pores posterior and anterior to vulva was described as a diagnostic character of Paratrichodorus (A.) porosus, formerly known as Trichodorus porosus originally described by Allen. However, in natural population of the species infesting Chinese yam at Matsushiro, Nagano, Japan, aberrant specimens lacking posterior one of a pair of postvulval pores were found in about 30 percent of the adult females. An isolated single culture of females was conducted attempting to clarify whether this diversity of morphology means a different species or merely intraspecific variation. As the results, it was indicated that the number of the pores varies within progeny from a single female so frequently as those in the natural population, and this character can not always be used as a diagnosis of this species. Parthenogenetic reproduction was apparent in this species by a single culture of larvae. Optimum temperature for reproduction in this population appeared relatively low, because the largest increase in population was shown by duplicated experiments at 20°C followed by 25°C and 30°C. Polyphagous nature of this species was proved by host range tests; 35 host plants among 43 plant species tested. Corn, cabbage, okra, and marigold were excellent hosts.

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Relationships between developmental stages and amount of nutrient taken in by the rice cyst nematode, Heterodera elachista, were studied using substances labelled by the radioactivity. Rice seedlings were grown at constant 25°C in sterile sand on a screen sieve so that the roots can grow through the screen into a cup of nutrient solution. Water suspension of 77, 000 larvae per cup was added to the sterile sand 1 month after sowing. The inoculation was accomplished by replacing the infected sand by sterile one after 48 hr. The culture solution was replaced by the radioactive one 1) every 3 days until the last stage of nematode, or 2) for a limited period, that is, 32 P-orthophosphate for 3 days and ¹⁴C-urea for 5 days. The radioactivity of about 10 dried nematode specimens separated from the root tissues was measured by a windowless gas-flow counter. The amount of intake of radioactive substances during every 3 days increased gradually from the second larval stage to the fourth one with a peak shown by matured females which actively deposited eggs into the gelatinous matrix (23-26 days after inoculation). None of the intake was indicated 40 days after inoculation. Ratio of radiophosphorus content in the second stage larvae to that in the adults was 1 to 140, and ratio of radiocarbon was 1 to 4. Those ratios of radiophosphorus and radiocarbon contents in egg masses to adult females were about 15% and 55%, respectively.

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Black pepper fields at Tomé-Acu, near Belém, Pará, Brazil where a disease called “foot rot” caused by Fusarium. solani f. piperi has been occurring, were examinedfor the infestation by the root-knot nematodes, predominantly Meloidogyne incognita. Seventy-four fields and 10 plants from each field were arbitrarily chosen, and the roots in a small portion of rhizosphere of each plant were taken off and rated for the root-knot index. Results were that (i) only one field was found uninfested by the nematodes, (ii) 91% of plants examined were infested by the nematodes, and (iii) three fourths of plants examined were of severe infestation. The infestation of plants by the nematodes appeared comparatively slight on young plants less than 5-year-old, and also no correlation with soil types. No Radopholus similis has been found from this black pepper plantation, although plant symptoms of yellowing leaves appear somewhat similar to those caused by R. similis in Indonesia.

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A modification of the sieve funnel technique (SF-T) was examined for its efficiency to separate Meloidogyne incognita larvae and Helicotylenchus sp. in comparison with that of the double layers centrifugal-flotation method (DLC-M). Following to remove the water from the nematode suspension by a thin layer of absorbent cotton sandwiched between sheets of Japanese paper, it was settled in the Baermann funnel for 72 hr at 20°C. As the results, it was considered that the efficiency of SF-T in August was similar to that of DLC-M for M. incognita larvae and was higher than that for Helicotylenchus sp. When expressed by CV, the variability of numbers of M. incognita larvae extracted was regarded as about 10%. The motility of M. incognita larvae decreased during winter but recovered after the incubation at 20°C for 48-72 hr. Such a decrease in the motility in winter did not appear for Helicotylenchus sp. In soil, a considerable proportion of M. incognita larvae died or was dying in winter and early in spring, but comparatively fewer Helicotylenchus sp. did in, that season. This method can be used for the quantitaive estimation of the.living larvae of M. incognita in soil without any effect of temperature on the motility, of the, nematode.

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Twenty-two populations or seven species of Pratylenchus collected from several locations in Japan were propagated on alfalfa callus tissues cultured by the modified Schenk and Hildebrandt's medium at different temperatures ranging from 15 to 34°C and pH of the medium from 2.9 to 8.1. As the results, the most favourable temperature for propagation varied according to the populations or species tested ; it was 25°C for P. penetrans, P. fallax, 3 populations of P. vulnus, P. loosi, and P. crenatus, 25-30°C for another population of P. vulnus, 25-32°C for P. coffeae, and 29-34°C for P. zeae. No ignificant effect of the initial pH of the nutrient medium on the propagation of the nematodes appeared except for few populations or species, i.e., P. fallax Pop.2, P. loosi Pop.s, and P. vulnus Pop.3 which decreased the rate of propagation at a low pH.

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