1979] 
Uetz & Burgess — Behavior in M. spinipes 83 
Table 1. Distribution of Metepeira spinipes in several microhabitat types. 
Microhabitat 
Agave 
Opuntia 
Trees 
Shrubs 
Grasses 
+ Forbs 
percent cover 
4.3 
1.0 
4.6 
5.0 
85.1 
percent volume 
4.9 
2.3 
20.9 
7.6 
64.4 
No. of spiders 
691 
16 
2 
96 
17 
No. of colonies 
X colony (+2 S.E.) 
47 
I 
0 
9 
3 
size 
No. of solitary 
14.67±3.38 
16.0 
— 
14.89±8.1 
2 . 0 ± 0.0 
individuals 
2 
0 
2 
2 
11 
Tests of significance: 
no. of solitary 
no. of spiders no. of colonies individuals 
H„ = equal frequencies in all microhabitat types 
X 2 = 2141.8 x 2 = 93 7 X 2 = 22.12 
P < 001 p < .001 p < .01 
Ho = frequencies proportionate to percent cover of micro-habitat type 
X 2 = 12922.1 ft = 646.7 ^2 = 6.9 
P < -001 p < .001 .2 < p < .3 
Ho = frequencies proportionate to percent volume of micro-habitat type 
X 2 = 11188.0 ft — 55] 5 ^2 = 3 u 
P < 001 p < .001 .5 < p < .6 
spinipes aggregations arise from some kind of interattraction, not 
from habitat patchiness. 
Another means of gathering evidence for or against a social ten¬ 
dency to aggregate is an analysis of the frequency distribution of 
group size. In a study of web-clumping in Nephiia clavipes, Farr 
(1977) compared group size distributions to a Poisson distribution 
truncated at zero. His data fit the distribution, and he concluded 
that web clumping by N. clavipes is a random process. Using 
methods described in A Cohen (1960) and J. Cohen (1971), we 
attempted this with data on M. spinipes group size from two con¬ 
trasted habitats (the maguey plantation and the willow shrub ditch 
described in methods). In both habitats, the distribution of spider 
