Abstract
In 1955 and 56,observations were conducted on the root aphids injurious to upland rice and the ants attending these aphids in the upland rice fields in Shozima city near Tokyo. The root aphids concerned were Rhopalosiphum prunifoliae, Anoecia corni and Tetraneura ulmi and the species mentioned first was more dominant than the others in June and July. Six species of ants were found in the field studied and four species, Lasius niger. Crematogaster sordidula osakensis, Pheidole fervida and Tetramorium caespitum jacoti, were observed attending the aphids. In a few cases when the soil was loose and light or there was any tunnel worked by mole cricket, the aphids seemed to go under soil without any help of ants, but there was a close positive correlation between the number of aphids and ants found in sampled soils taken at random in the fields. This correlation was observed till the middle of the season. Some ants were observed carrying the apterous female and nymphs of Rhopalosiphum prunifoliae into their hole, indicating their important role in assisting the migration of aphids from soil surface to the subterranean habitat. The frequency distribution of the numbers of both aphids and ants were not random but strongly contagious. The variance (s^2) of the average number of aphids was found to increase proportionately to their population density as shown in Fig. 1. Thus the frequency distribution of aphid numbers can be transformed into normal one if the actual numbers are changed into log_10(x+1).
