Ecological Researches on the Wireworm, Melanotus caudex Lewis

Abstract

1. Population censuses on the wireworm, Melanotus caudex Lewis, which were limited to the individuals larger than the 2nd-year old, were taken in spring on barley field and in autumn on Chinese cabbage field in 1957. 2. The distribution pattern of the individuals in each section and that beside each plant root in both seasons were in accord with the frequency distribution of Pólya Eggenberger type. χ2 test of the fitness was better in the case of plant root than that on the section. 3. To estimate the wireworm population, the counting on the number of worms living beside a plant root is more convenient, because the worms living in a section outside a root of Chinese cabbage are fewer than those living beside a plant root. 4. The explanation of the concentrating nature of the distribution pattern of the wireworm is as follows; a) the oviposition of the adult insect takes place individually in the soil surrounding the crop plant; b) the wireworm living near to the soil surface feeds on the crop plant and creeps into it; and c) the wireworm dwells just under the plant, when it creeps into the deeper layer of top soil. 5. Among the factors opposing the concentration of the wireworm to crop plant, the scattering of concentrated worms due to soil preparation for wheat (in autumn) and sweet potato (in spring) was taken into consideration. But it did not have a great influence on the dispersion of the wireworm larger than 2nd-year old for the disturbance of soil surface occurred after the wireworm sank into the deeper layer of top soil. As a natural enemy of the wireworm, a species of Bethylidae was collected. It has any great influence on the distribution of the worm. 6. The frequency distribution in the barley field showed almost the same tendency as in the field of Chinese cabbage. © 1958, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.