FINE STRUCTURE OF THREAD CONNECTIONS 
IN THE ORB WEB OF ARANEUS DIADEMATUS 1 
By Robert R. Jackson 2 
Division of Research 
North Carolina Department of Mental Health 
Raleigh, North Carolina 
INTRODUCTION 
Web-building spiders are valuable subjects for the study of be- 
havior since the spider provides a record of much of its behavior 
through its web. Descriptions of the gross structure of the web and 
the behavior of the spider during its construction can be found in 
Savory (1952), Jacobi-Kleemann (1953), and Witt, Reed, and 
Peakall (1968). However, the gross structure is only part of the 
spider’s creation. The threads from which the web is constructed 
are only several microns thick. Consequently, the unaided human 
eye can determine basically only the position of the threads. 
Another part of the spider’s creation is visible only with magnifi- 
cation. This is the fine structure of the threads where they connect 
to one another. Rapidly produced and possessing remarkable strength 
( DeWilde, 1943), thread connections are one of the more interesting 
accomplishments of the spider. However, little attention has been 
given to the fine structure of the web. Lehmensick and Kullmann 
(1957) and Friedrich and Langer (1969) examined spider silk by 
electron microscopy, but did not look at points of connection between 
threads. McCook (1889) and Nielsen (1931) have drawings of 
attachment disks for drag-lines made under low magnification. De- 
Wilde (1943) has a photomicrograph of a radius to frame connec- 
tion, and Comstock (1948) has a drawing from a photomicrograph 
of a spiral to radius connection. Robbins (Savory, 1952) has a 
photomicrograph of a drag-line attachment disk and one of sticky 
spiral to radius connections, both at low magnification. Also, there 
is a photomicrograph of a spiral to radius connection from the hori- 
This work was carried out in the laboratories of the North Carolina 
Department of Mental Health and was supported in part by a grant from 
Hoffman-LaRoche, Inc., Nutley, New Jersey, and by Grant Number GB- 
6246X1 from the National Science Foundation to Peter N. Witt. The assist- 
ance of Dr. Peter N. Witt during all stages and Dr. Charles Walcott during 
the preparation of the manuscript of this work is gratefully acknowledged. 
2 Mailing address: Robert R. Jackson, Department of Zoology, University 
of California, Berkeley, California 94720. 
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