1978] 
Jackson & Smith — Mallos and Dictyna 
71 
Some of the larger communal webs of M. gregalis in the 
laboratory had surface areas and volumes estimated to be as large as 
1300 cm 2 and 1500 cm 3 . If the densities in these large webs were 
comparable to those in smaller webs, they can be estimated to have 
contained 300 to 700 spiders. Based on the descriptions of Diguet 
(1909a, b) and Burgess (1976), 4 m 2 will be used as an approximate 
estimate for the surface area of larger communal webs on trees in 
Mexico. If densities in nature are comparable to those in the 
laboratory then these very large webs may have contained as many 
as 20,000 spiders. 
WEB OCCUPANTS 
Solitary species, including M. niveus , usually occurred one spider 
per web (Jackson, 1978a), and this was true of all censused webs in 
the aggregations of M. niveus. However, each occupied web unit of 
the three communal, territorial species usually contained a set of 
several spiders. These could be almost any combination of females, 
males, and immatures of varied sizes (Table 3), except that web 
units were never shared by two adults of the same sex. In the only 
instances in which male-male or female-female pairs were seen 
together in the same web units, aggressive interactions took place, 
after which one individual departed. In contrast, large numbers of 
M. gregalis belonging to all sex/ age classes shared the same 
communal webs without aggressive behavior or cannibalism. 
DISTRIBUTION OF WEB OCCUPANTS 
Large proportions of each sex/ age class of M. trivittatus occupied 
the nests (Tables 3 and 4); but adult females were especially prone to 
be inside nests, and there was a preponderance of immatures in the 
interstitial web. These data were consistent with more casual 
observations of M. trivittatus in other locations and of the other 
communal, territorial species. During the day, M. niveus and other 
solitary species were most often, but not always, inside nests. All M. 
niveus in censuses were inside nests. 
Many hours of casual observation in the laboratory gave the 
impression that adult males and immatures of M. gregalis were 
more prone to be on the outer surfaces of webs, and females were 
more prone to be in the interior. (Data related to this will be 
presented below.) 
