1977] 
Jackson — Dictyna and Mallos 
275 
Feeding Groups — Size and Composition 
The few cases in which more than one spider fed on the same 
prey in species other than M. gregalis are described elsewhere 
(Jackson, 1979b). In the laboratory, the size and composition of 
the group feeding on the fly was recorded 15 min after it contacted 
the web, and cases in which no spiders were feeding at the end of 
the 15 min are excluded. Group size was 4.8 ± 2.96 spiders (range: 
1-15; n = 38). In the cases in which a single spider fed on the fly, 
three were females, two were immatures, and none were males. One 
of the immatures was a second instar; the other was almost adult size. 
In cases in which more than one spider fed on the fly, there were 
three groups consisting of females only; 4, immatures only; 21, 
females and immatures but no males; 2, males and immatures but 
no females; and 3, females, males, and immatures. In more casual 
observations, single males feeding on flies and groups consisting of 
females and males but no immatures were seen; but groups of more 
than one male but no females or immatures were not noticed. 
Groups of more than 20 individuals have been seen. 
Discussion 
Based on arthropod carcasses found in webs and observations of 
actual feeding in nature, Diptera seem to constitute the major prey 
of the closely related species of Dictyna and Mallos in this study. 
Billaudelle (1957), Bristowe (1958), and Wiehle (1953) commented 
on dictynids preying on Diptera, ants, and lice. Unfortunately, 
only limited information is available concerning the natural prey 
of M. gregalis, the communal, non-territorial species. I was not 
able to find this species when I was in Mexico. Diguet (1909a, b, 
1915) and Burgess (1976 and personal communication) noted that 
Diptera seem to be the primary prey of this species in nature, al- 
though wasps are also fed upon. The Diptera seem to be predom- 
inantly ones of body lengths of approximately 5 to 10 mm, such 
as the “domestic fly” (presumably Musca domestica), tabanids, and 
bot flies. Burgess collected a portion of a web in Mexico; and 
when examined in the laboratory, it contained a great number of 
carcasses, all of Diptera in the size range of 5 to 10 mm. In the 
laboratory, M. gregalis has thrived for several years on a diet of 
M. domestica almost exclusively. The natives of Michoacan have 
