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Psyche 
[Vol. 87 
Results and Discussion 
TOLERANCE 
Well-fed M. gregalis are tolerant (i.e., non-cannibalistic and non- 
aggressive), and the present study indicates that they remain tolerant 
to what seems the ultimate extent: when kept without alternative 
prey, they starve to death rather than resort to cannibalism. 
No M. gregalis was seen feeding on conspecifics, and none of the 
dead ones had the appearance of having been eaten. When spiders 
contacted other living or dead conspecifics, they simply walked away, 
either immediately or after briefly tapping with their legs. 
Although it is tempting to view the absence of cannibalism in M. 
gregalis as altruistic and to entertain familiar hypotheses such as kin 
selection (e.g., Wilson, 1971), a cautionary remark seems appropriate. 
Few observations have been made on these spiders in their natural 
habitats, and how often colonies encounter shortages of insect prey is 
unknown. However, considerations of this sort seem important in 
assessing whether, and if so to what extent, tolerance is altruistic, 
especially since the issue is not something the spiders do but 
something they fail to do. 
SEX AND SPECIES DIFFERENCES IN SURVIVAL 
In the colonies left indefinitely without insect prey, males died 
sooner than females (Fig. 1; Mann-Whitney U-test, t = 5.599, P< 
0.001). No males survived beyond 23 days, although females and 
immatures survived as long as 53 days. There were no evident 
differences in survival times for females and immatures. 
Male spiders may generally be adapted to a lifestyle that emphasizes 
courtship, mating, and searching for females at the expense of 
maintenance functions that serve to prolong survival (Ghiselin, 1974; 
Jackson, 1978c). The earlier deaths of males in colonies maintained 
without prey would seem to be a reflection of this in M. gregalis. 
Perhaps males lack the capacity to store nutrients to get them 
through periods without prey, or possibly they are behaviorally 
and/or physiologically more active and require greater amounts of 
nutrients per unit time than females and immatures. 
However, the difficulty in keeping males of M. gregalis alive seems 
also to be a reflection of differences in the biology of this and the 
other two species. When provided in their own webs with insect prey, 
many males of M. gregalis died; but only a few of those of the other 
