1971] 
Jackson — Web of A raneus 
23 
terns during web construction? The spinnerets are capable of “to 
and fro” and complex rotary movements (Wilson, 1969). It would 
be interesting to observe these movements during the construction 
of each type of thread connection. For example, there may be 
differences in construction procedures on this level which can be 
related to the manner in which the fine structure of SS-R’s differs 
from that of NS-R’s and PS-R’s. Also such observations might pro- 
vide information about the origin of some of the structures at thread 
connections. 
The production of radii, NS’s, and PS’s, is attributed to the 
ampullate glands. The aggregate glands, to which production of the 
viscid globules is atributed, are not believed to be involved (Peakall, 
1969). Some spiral and radial threads at NS-R’s and PS-R’s re- 
sembled radii at SS-R’s in having loose strands and no globules, 
However, one PS-R had tiny globules, smaller than those on SS’s 
on a thin (0.5 jjl — 1 /x) strand (Fig. 4b). How were these pro- 
duced, and what glands were involved? 
Table 4 
Descriptive statistics for some structural features of connections from the 
strengthening zone (NS-R’s). For each feature 2 webs built by different 
spiders were observed. NS-R’s were rather variable with respect to these 
features, as indicated by the coefficients of variation. Comparing this table 
with Table 2, note the increased length of the junction and the decreased i 
thickness of the radius. Thread thickness was measured at both sides of the 
junction. 
Coefficient 
No. of 
of 
Measure- 
Feature 
Mean 
Variation 
Range 
ments 
Length of Junction 
137.4 /* 
29 
75 jjl-225 H 
18 
Number of Strands 
at Junction 
8.9 
49 
4-22 
18 
Thickness of Radius 
3.9 li 
41 
1 P--7 n 
35 
Thickness of NS 
3.1 fM 
29 
2 /1-5 li 
32 
