60 
Psyche 
[Vol. 87 
remains, then one would expect a similar ring of excreta to surround 
the web site in the laboratory. 
The present study quantitatively investigates the distribution of 
excreta as related to web structure and the distribution of spiders 
within experimental colonies in order to determine the possibility of 
systematic sanitary behavior in this species. The effects of group size 
and available building space on excreta distribution are also 
described. In addition, methodologies utilizing a computer-camera 
apparatus for data collection are presented. 
Methods 
I General Methods 
M. gregalis from a colony collected by G. W. Uetz near Mexico 
City, Mexico in 1979, was maintained in a climate-controlled room 
(T=25±5°C, RH=90±10%, natural photoperiod). Animals were 
daily given a fine spray of water on the surface of the web and were fed 
houseflies (Musca domestica ) at weekly intervals. 
One week prior to data collection, about 200 individuals were 
removed from the above colony; divided into approximatly equal¬ 
sized groups; transferred to four glass containers (13cm dia, 17cm 
height) and allowed to build webs. On the fifth day each group was 
fed 10 flies and two days later the colonies were split into samples for 
experimental analysis. Three group sizes (N=5, 10 or 20 adult 
females) were released into two different-sized petri dishes (large=96. 
lcc, small=52.2cc). Each group was allowed a two-week period (28 
May-11 June 1980) to build a web. During this time they were not 
fed, but were watered daily by putting droplets of water near the edge 
of the petri dish. Photoperiod was natural for this summer time of 
year in North Carolina and temperature was 26.3±1.1°C. 
II Recording Methods. 
Detailed recording methodologies will be presented elsewhere 
(Tietjen, in prep.) or are available from the author. In brief, a solid- 
state television camera (Perificon type 511 image digitizer) was 
connected to a CDP-1802 microprocessor-based computer via a 
suitable interface. The computer acted as an “intellegent controller” 
of the camera and, through appropriate software (see below), could 
regulate the exposure time, number of frames per sec and the 
formating of data. Data were stored in computer memory during 
collection and were transferred to magnetic tape for future analyses. 
The camera provided a potential matrix array of 32 X 32 picture 
