1978] 
Jackson & Smith — M alios and Dictyna 
77 
ever, another factor that must be considered is that the two types of 
censuses were made at different times of the year, and differences 
may be influenced by phenology. 
CAUSES OF DISTRIBUTION PATTERNS WITHIN WEBS 
In all species, eggs tend to be oviposited in the vicinity of the 
nests, and the tendency for females to be found in nests is probably 
at least partly related to this. Also, nests may be optimal resting sites 
with respect to protection from predators and parasites (Jackson, 
1978a). If obtaining space within a nest is accompanied by aggres- 
sive behavior, which seems likely in the communal, territorial 
species, then females may have an advantage related to their larger 
size. Females in each species have the largest body size of any 
sex/ age class. Compared to males, females may be more sedentary; 
and a stronger tendency to occupy nests may be related to this. This 
might also apply to comparison of females with immatures if the 
immatures are the dispersal phase in the life histories of these spe- 
cies. Also, by virtue of their smaller size, young immatures may be 
safer from predation on the mesh or interstitial web than females, 
since they might take refuge under strands of silk, particles of 
debris, etc., which are too small to be effective for females. As a 
result, there might be lesser selection pressure against immatures 
that remain outside nests compared to larger females that remain 
outside nests. 
Since females seem to be prone to be in the interior of webs of M. 
gregalis, we might expect males to spend considerable time search- 
ing for and courting females in the interior of webs. Instead, more 
males seem to be on the exterior surfaces of the webs. In M. gregalis, 
unlike M. trivittatus and D. calcarata, the presence of females and 
silk spun by females are not releasers of courtship behavior. Instead, 
males seem to have an advertising routine, as part of their daily 
activity pattern, in which they perform behavior referred to as 
“pluck-walking.” Females seem to indicate their receptivity to 
pluck-walking males by failing to run away (Jackson, 1978b). We do 
not know the factors that determine female receptivity, but perhaps 
receptive females are more likely to be on the outer surfaces of webs. 
For example, females might be unreceptive near the time of 
oviposition, and oviposition takes place in the interior of the web. 
Although the difficulty of observing behavior of spiders in the 
interior of webs should be kept in mind, it is of interest that the 
