84 
Psyche 
[March 
group size was significantly different from a zero-truncated Poisson 
distribution (Tables 2 and 3), indicating a non-random grouping 
pattern. The distribution did fit a zero-truncated Negative Binomial 
distribution (Tables 2 and 3), indicating a significant tendency to 
aggregate. The fact that group size in M. spinipes occurs with the 
same underlying aggregated distribution in such divergent habitat 
types argues for the existence of a social grouping tendency rather 
than fortuitous aggregation. While it may be argued that in Agaves, 
structural habitat resources are concentrated in small patches, this 
was not the case in the willow shrubs. The willow shrubs appeared 
to be uniformly dense and of equal height and age. There was no a 
priori reason to suspect that web site resources for M. spinipes 
Table 2. Frequency distribution of group size in Metepeira spinipes colonies in 
Agave plants. 
Group Size 
Observed 
Frequency 
Truncated 
Poisson 
Truncated 
Negative 
Binont’ 
1 
0 
.0001 
.651 ( 
2 
0 
.0009 
.811 I 
3 
I 
.005 j 
.914 1 
4 
2 
.017 ( 
) 1.71 
.977 ( 
5 
0 
.050 , 
1.010 
6 
2 
.124 I 
1.010 
7 
0 
.259 ' 
1.010 
8 
2 
.475 
.9881 
9 
0 
.775 
.958 f 
10 
0 
1.136 
.9201 
11 
0 
1.515 
.881 ( 
12 
1 
1.850 
.840 ( 
13 
2 
2.090 
.790 / 
14 
1 
2.190 
.7451 
15 
1 
2.140 
.699 ( 
16 
0 
1.960 
.6541 
17 
1 
1.690 
.6101 
18 
0 
1.38 
.5701 
19 
1 
1.06 
,530| 
20 
>20 
0 
7 
.78 i 
1.50 ( 
2.28 
.49 1 
5.95 ( 
1.46 
1.89 
1.95 
1.80 
1.63 
1.44 
1.26 
1.10 
6.44 
X 2 = 34.06 x 2 = 11 -98 
p < .005 .5 < p < .6 
