104 
Psyche 
[Vol. 87 
distinguish. Last, Fritz Vollrath collected what is probably W. 
galapagensis Archer from the Cocos Islands off the coast of Costa 
Rica, and noted on his collecting label, “second growth, single 
thread.” Currently, there are five other neotropical species placed in 
Wendilgarda. Of these, two are apparently known only from the type 
specimens, and the webs of none of these species are described. 
Although it is likely that a few of these names may have to be placed 
in synonymy when the genus is revised, we predict that all species of 
Wendilgarda will be found to spin these peculiar webs. 
Wendilgarda species have evolved a web that exploits a hitherto 
unknown property of silk fibroins. Obviously, the chemical nature of 
the silk, or silks, composing the sticky lines of Wendilgarda webs and 
their glandular source, as well as the molecular details of the silk- 
water junction are extremely important in the function of the web and 
require further study. Such facts as the amount of tension the web is 
normally under, or the amount it will maximally sustain, are being 
investigated. In addition, the relationship of the Wendilgarda web to 
the modified orb-webs constructed by other members of the family, 
and the behavior patterns used to construct it, may allow inferences 
about the evolution of the web architecture that so precariously 
straddles the terrestrial and aquatic environments. 
Summary 
We describe the web of the spider genus Wendilgarda. The webs of 
the three species thus far are indistinguishable in the field. They 
consist of a dendritic pattern of non-sticky horizontal lines spun 
above the surfaces of moving streams. Extending from the horizontal 
non-sticky lines are vertically oriented sticky lines that terminate at 
the surface of the stream. The ends of the vertical sticky lines are 
attached only to the surface film of the stream. The entire web is 
under considerable tension, and the tension is opposed by the sticky 
line-water function. We describe how the web functions, how it it 
used in the attack behavior of the spider, and suggest that the 
architecture of the Wendilgarda web can be related to the modified 
orb-webs characteristic of other theridiosomatid spiders. 
