68 
Psyche 
[March-June 
TABLE I 
A. trifolium 
II 
Tibiae 
347 
0.54 
2.75 ±0.60 
12.0 
Tibiae I 
41 
0.61 
2-39 ± 1.36 
4.8 
A 
Total 
count 
210 
0.63 
4.43 ± 1.00 
11.6 
marmoreus 
Dentiform 
only 
210 
0.42 
1.44± 0.56 
6.7 
N 
n 
b 
t-test 
(for b — 0) 
Calculation of correlation and regression coefficients for spine counts 
versus lengths of first and second tibiae of A. trifolium and for total and 
dentiform spine counts versus length of second tibia of A. marmoreus. ri 
is the correlation coefficient for spine counts versus length ; b is the slope 
of the regression line, presented with its 99% confidence intervals. The 
significance of the correlation may be found either from the value of the 
coefficient r or from the t-test on the null-hypothesis b — 0. 
fact the case.) While this does not affect the validity of the results 
as they have been presented, it would modify the quantitative rela- 
tionship (expressed by b) significantly in separated areas. This ques- 
tion is open to further study; its significance will be mentioned 
below. 
Conclusion 
The correlation between the number of spines on a segment and 
the length of the segment is important to at least two aspects of 
Araneology: taxonomy and the study of geographic variation. Mac- 
rosetal counts have often been used to distinguish between different 
genera of spiders 2 , as well as between species of one genus such as 
Araneus. If the situation described in this paper is a general one, 
then clearly any character based on setal counts should be used for 
taxonomic purposes only after careful study. In general, it would 
seem from observations on these two species of Araneus that the 
number of spines alone is not highly reliable, but the pattern is quite 
constant within a species (or at least recognizable, though spines 
may be missing, or present in “unusual” locations). This is sup- 
ported by observations made on species of the genus Neoscona (Ber- 
man and Levi (1971), p. 467 ) . 
Secondly, in studying geographic variation, it is necessary at least 
in this case to consider the mean dimensions of local populations as 
well as the spine counts. A marked variation in spine count between 
2 For examples, see Kaston (1948), with reference to: Gnaphosidae 
(Drassodidae) pp. 347, 354; Clubionidae, pp. 367, 382; Thomisidae, pp. 
410, 440; and Salticidae, p. 445. 
