42 
Psyche 
[March-June 
General Discussion 
The males grow until the last molt, at which time they attain 
their maximum weight; weight decreases slowly thereafter. The 
females have a distinctly different course of growth; their weight 
increased long after the last molt, generally until they lay a cocoon. 
The males mature more rapidly than the females, but the females 
grow bigger than the males and live longer. 
The females and the males of each of the two sets of Araneus 
diadematus studied are clearly divided into FG and SG. The FG 
males are characterized by a higher frequency of building, rate of 
food consumption, rate of weight increase, rate of leg growth, rate 
of maturation as well as a smaller number of molts than the SG 
males, significant only for set I in the last instance. 
The positive correlation between the rate of building and the rate 
of food consumption for all males must be expected, since the spiders 
were fed only when they had built a web. The different frequency 
of building may be explained as a lower threshold for web-building 
through hunger in the FG than in the SG spiders. The number of 
prey captured is a function of behavior mechanisms of the spider and 
potential prey; among the former are the stimuli that induce the 
spider to attack, the efficiency of this attack, and also a number of 
other variables such as web-site, web-characteristics, and frequency of 
building. The hunger stimulus which induces both, the attack and 
web-building, has a lower threshold for the FG than for the SG 
spiders, suggesting that in a natural habitat the FG males would be 
able to capture and eat more food than the SG spiders. In addition, 
the usual effect of genes on animals with rigid patterns is to alter 
behavior in a quantitative, rather than a qualitative, fashion (Mann- 
ing, 1967). The environmental conditions being the same for all 
the animals, the difference in threshold of hunger may be the conse- 
quence of different genotypes. 
A relationship between the rate of food intake and the rate of 
growth indicates that the food was converted into spider tissues, in 
addition to maintain basal metabolism and to support the necessary 
activities like prey catching. The percentage of food converted into 
spider tissue was higher for the FG males than for the SG males, 
explaining the different growth rates. The same mechanism could 
provide a more ample supply of silk for the FG than for the SG 
males, which is suggested by the analysis of the web dimensions of 
