Seasonal fluctuations, namely, seasonal changes of the rise and fall, of the instar composition, and of the distribution pattern of both species were examined during the rice crop season in a paddy field in Sakai in 1970. Their seasonal changes showed patterns which have only one peak during the rice crop season. The maximum number of O. insecticeps was shown on the last day of September when 425 individuals were counted on 25 stubbles. The maximum number of E. japonica was shown early in October with the density of 294 individuals per 25 stubbles. It seems that the rate of predation of O. insecticeps increases in early and mid August and again from late September to the harvest time, and that of E. japonica increases from late July to early August and again in late October. It is concluded that both species have a specific pattern of distribution respectively which varies according to the stage of their development.
Thirty spider species belonging to 12 families were recorded from cabbage fields in the preliminary survey made at Shimobaru in Fukuoka in May, 1975. Theridion octomaculatum B. et S. and Oedothorax insecticeps B. et S. were the most abundant throughout the 9 study plots. Diets of these two species were mainly composed of small-sized miscellaneous insects of Hemiptera and Diptera. Spiders of the cabbage fields were revealed to be similar to those of the paddy fields as to the spider-fauna and major species. Spatial distribution of T. octomaculatum was nearly uniform, suggesting that strong mutual interference was occurred among individuals.
Chiracanthium japonicum, the most common spider making house with leaf of Graminaceae, is well known as venomous for a person. During the period from 1956 to 1974, five bite cases of this species were reported from various districts in Japan. These cases were classified by the severity of clinical manifestation into four types, symptomless, mild, moderate and severe. Four bite cases in all cases were occurred by male and two bite cases were of the severe type. The most serious problem in the trearment was difficulty in relieving continuous sharp pain by any anodynes or sedatives.