20 
Psyche 
[March-June 
SS-R’s in approximately ten minutes. Taking this into consideration, 
it is not surprising that there is a great deal of variation in connection 
structure and that SS-R’s have idiosyncrasies. 
Globules (Fig. 2d), presumably containing the viscid material, 
were seen on SS’s in the vicinity of the junction, but none were seen 
on radii. There was a variable amount of space between the junction 
and the nearest globule. Observations of SS’s at positions other than 
the vicinity of SS-R’s produced the impression that the space 
density of globules (number of globules within a given length of 
thread) was rather constant. In contrast, the number of globules 
within 200 fi of both sides of the radius at a SS-R was quite variable. 
Stretching the SS is the probable cause of the accumulation of viscid 
material into globules (Savory, 1952). The radius may interfere 
through being a discontinuity in the stretched line and, in this way, 
be responsible for the less uniform distribution of globules near the 
junction. 
It is believed that the ampullate gland produces the silk for the 
radii and the baseline of the SS’s, with the aggregate glands producing 
the viscid material (Peakall, 1969). However, the radial thread is 
not simply equivalent to a viscid spiral thread minus the viscid 
material because the radial threads we observed were generally 
thicker than SS’s, although both had the same minimum thickness. 
Also, DeWilde (1943) found that viscid spiral threads are much 
more extensible than radial threads, and we observed loose strands 
(Fig. 2d) along the radii in the vicinity of SS-R’s but never on SS’s. 
Connections from the Strengthening Zone and Provisional Spiral to 
Radius Connections: 
Table 3 and Table 4 contain data pertaining to NS-R’s. The 
motion pattern of the spider differs during construction of NS-R’s 
and PS-R’s on the one hand and SS-R’s on the other. The fourth 
pair of legs are relatively motionless and touching the radius as a 
NS or PS is fastened to a radius. However, as the spinnerets touch 
the radius in generating a SS-R, one of the fourth legs stretches 
the SS. In comparison to NS-R’s and PS-R’s the construction of 
SS-R’s apears slow and deliberate (Savory, 1952). There are also 
differences in the fine structure of these connnections. 
Junctions of NS-R’s (Fig. 3) were usually much longer than 
those of SS-R’s. There were no zero junctions. In contrast to SS-R’s, 
neither radial nor spiral threads ever appeared as continuous lines at 
NS-R’s. This created the notched appearance of the strengthening 
