30 
Psyche 
[March-June 
mine sulfate, ioo mg/kg). However, they do not normally occur 
in the vertical web of A. diadematus. 
Possibly the material from the piriform glands is a cement. Does 
it cement the drag-line to the substrate through fusing to both, or 
are the threads from the piriform glands themselves cemented at one 
end to the dragline and at the other to the substrate? 
Stretching may be responsible for solidification of fluid silk through 
causing filaments to slide past one another, assuming positions which 
allow for a greater degree of cross linkage (Lucas and Rudall, 
1968). Another hypothesis of junction formation is that fluid silk 
for the new thread fuses with the old thread as it solidifies. As the 
spinnerets sit on the old thread, some fluid silk departs from the 
spigot of the ampullate gland (and the spigots and spools of any 
other gland involved). Solidification does not occur because there 
is insufficient stretching of the material. When the spinnerets are 
lifted and sufficient stretching occurs, the new silk solidifies and is 
fused to the old thread. 
More information will be necessary before we can choose between 
these hypotheses. Perhaps different mechanisms occur at different 
types of connections. Also, it may become necessary to somehow 
modify or combine these hypotheses. 
SUMMARY AND CONCLUSIONS 
The fine structure at thread connections in the web of Araneus 
diadematus was examined by photomicroscopy. Characteristic struc- 
tures were discovered for each connection type including presence of 
sleeves on threads, various lengths of junctions, various numbers of 
strands, and different distributions of globules. Possible functions 
and origins of structures were discussed. There was a discussion of 
two hypotheses related to connection formation: a) threads are 
cemented together, and b) new thread, while in a semi-solid state, 
fuses to old thread. 
This survey is only a modest beginning in the direction of study- 
ing the fine structure of thread connections. With a more extensive 
and systematic investigation, rigorous statistical comparisons could 
be made of different types of connections and of the same type of 
connection from different regions of the web. Structure could be 
compared for spiders of different age, weight, and species. Viewing 
the fine structure of connections has led to many interesting ques- 
tions. Some were mentioned in this paper; others have probably 
occurred to the reader. Hopefully, these will be pursued further 
in future studies. 
