268 
Psyche 
[September-December 
tory. Also, arthropod carcasses in webs were collected and iden- 
tified. Data are given as means ± S.D. 
Most dictynid species are solitary, each individual generally liv- 
ing alone in an individual web that does not touch other occupied 
webs. Communal, territorial species (M. trivittatus Banks, D. al- 
bopilosa Franganillo, D. calcarata Banks) live in web complexes, 
consisting of web units connected to each other by silk. M. gregalis 
Simon (communal, non-territorial) lives in communal webs not 
subdivided into web units. Aggressive and cannibalistic behavior 
are virtually non-existent in this species, and individuals routinely 
feed in groups on the same prey. The other species are aggressive 
and cannibalistic, and most often they feed one spider per prey. 
In this paper basic information concerning the feeding behavior 
and diet of varied species will be presented, and a specific hypoth- 
esis will be discussed: namely, is predation on relatively large and 
dangerous prey an important factor in M. gregalis? Other aspects 
of the feeding behavior of M. gregalis have been reported elsewhere 
(Burgess, 1975; Jackson, 1979a; Witt, et a/., 1978). 
Data concerning M. gregalis were gathered in conjunction with 
another study (Jackson, 1979a) to which the reader should refer for 
a description of laboratory methods. “Large webs” were communal 
webs built on plants in the laboratory, each probably containing 
several hundred spiders (Jackson and Smith, 1979); and these were 
not enclosed. “Small webs” (built by four spiders each) and “single- 
female webs” were built inside plastic cages. Data concerning where 
the spider first grasped the fly came from all three types of webs; 
data concerning size and composition of feeding groups came from 
large webs only. 
Diet 
Diptera were the predominant prey upon which Dictyna and 
Mallos were observed feeding (Table 1), and these dominated the 
collection of carcasses (Table 2). The data in Table 2 should be 
viewed as a list of probable rather than certain prey of these species, 
since some were possibly not fed upon by the dictynids. Two small 
Diptera in webs of M. niveus and one small Diptera in a web of 
D. tridentata were still filled with hemolymph. Probably these 
were captured flies on which the spiders had not yet fed completely, 
this species came from spending many hours observing a particular 
