The common cabbage butterfly, Pieris rapae crucivora (BOISDUVAL), the Asiatic common looper, Plusia nigrisigna WALKER, and the cabbage armyworm, Barathra brassicae LINNÉ are important lepidopterous pests on cabbage in Japan. The writer made a series of observations on the population dynamics of these insects at Hirosaki, near the northern tip of Honshu, throughout the season from mid-April to mid-October in 1959. In the present paper, the results of observations on the seasonal fluctuation in the numbers of eggs of these species deposited on cabbage plants are described. The following table would be made as the summary of the main results of this paper. The peak of oviposition in these species did not overlap each other throughout the season. A comparison was made on the number of eggs deposited on a plant between two cabbage-fields of different areas: a narrow one with 20 plants and the other with about 400 plants. It was found that both Pieris rapae crucivora and Plusia nigrisigna deposited their eggs more numerously on a plant in the narrow field than in the wide one. And reversed tendency was observed on Barathra brassicae; more eggs on a plant were found in the wide field than in the narrow one.
サツマイモネコブセンチュウ(Meloidogyne incognita var. acrita)に対する感受性を異にする6種,8品種の植物の根への幼虫の行動を調べた結果,その好適宿主であるトマト,甘藷農林1号ならびにタバコに多くの幼虫が集まった。この現象は根の誘引作用によるものである。しかしながら,根からある程度離れた所では無方向性の運動をする。更に,幼虫は生長点附近に最も多く誘引されるがほかの部分にも誘引される。また,根部拡散物質にも誘引作用が認められることから,植物の根の線虫に対する誘引作用には根から分泌される,ある化学物質がある程度の役割を果たしているものと推定される。