Plexippus setipes was reared under constant temperature (27-28°C) and photo-peried (16 hours each day), and the following results was obtained. 1. The spiders moulted 5 to 6 times before they reached adulthood. 2. Durations of days in each instar were greatly affected by the food condition, the duration was shortened when feeding interval became short. 3. Total number of days required for the development from the first instar to adult was 110-200 days, excepting the period of immature nymphal stage staying in egg-sac.
HONDA, Shigeyoshi (Department of Zoology, Faculty of Science, Kyoto Uni-versity) On the method for quantitive analysis of web spider community (I), Ranks of dominancy among species in a community. A method for finding out the dominant species in a web spider community based on the line transect sampling was proposed. The rank of dominancy is estimated from the relative size of the mean space occupied by each species in unit space surveyed (1m in width, 5m in height and 1m in distance) along a survey route. The mean space occupied by a species (Os) is obtained by: OS=OI•DS where OI and Ds are the mean value of individual space occupation and mean number of individuals per 1m3 respectively. As a convenient method, the index method was also proposed in which the index of specific space occupation (IOS), instead of Os, obtained by the following formula is used: IOS=IOI+IDS where IOI=log OI and IDS=log DS=0.699 (NSC-8) in which NSC is the density class taking the unit based on the logarithm of the population density. As a result of application the method to the web spider community in an artificial forest of Cryptomeria, the ranks of dominancy of the species in this com-munity were estimated as: (1) Nephila clavata, (2) Cyclosa sedeculata, (3) Theridion takayense, etc.