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Psyche 
[Vol. 87 
(Jackson, 1977). M. trivittatus, D. calcurata, and D. albopilosa are 
communal, territorial. They live in web complexes divided into 
defended web units. One or a small group of spiders occupy each unit, 
separated from other units by interstitial threads. M. gregalis is 
communal, non-territorial; and hundreds or thousands of individuals 
occupy single communal webs not divided into defended units 
(Jackson & Smith, 1978). 
Aggression and cannibalism are pronounced in the solitary and 
communal, territorial species, but almost never observed in laboratory 
colonies of M. gregalis which were normally provided with insect 
prey (adult Musca domestica or Drosophila melanogaster) once or 
twice per week. This raises the question of whether cannibalism 
would occur if the spiders were nutritionally stressed. In casual 
observations of small colonies kept without prey for 3-4 weeks, 
cannibalism was not seen (Jackson, 1979b; P. N. Witt, pers. comm.); 
but considering the renowned capacities of spiders to resist starvation 
(Anderson, 1974), it is difficult to assess the nutritional stress to 
which these spiders were subjected. Consequently these observations 
were extended by keeping colonies of M. gregalis indefinitely without 
alternative prey in order to see whether the spiders would resort to 
cannibalism before starving to death. 
In these observations, it was noted that adult males died sooner 
than the adult females and immatures. More casual observations in 
the laboratory also indicated that adult males of M. gregalis were 
more difficult to keep alive, even if provided with insect prey, and that 
they differed in this respect from the other species of Mallos and 
Dictyna. Additional observations were carried out in order to clarify 
this aspect of the biology of these spiders. 
Methods and Materials 
The laboratory colony of M. gregalis originated from spiders 
collected by J. W. Burgess (1976) near Guadalajara, Mexico. M. 
trivittatus were collected in Arizona and D. calcurata near Lake 
Chapala, Mexico, by the author (Jackson, 1978a). 
Two types of transparent, plastic cages were used: small ones 
constructed from 9-cm-diameter petri dishes; large, from 10 x 10x6 
cm boxes. Details of cage design and maintenance are provided 
elsewhere (Jackson, 1974, 1979b). 
The terms “male” and “female” will be used for adults only. 
