96 
Psyche 
[Vol. 87 
Extending downward from each of the horizontal lines was a series 
of vertical threads made of sticky silk. The sticky silk lines never 
connected two horizontal lines, but only the horizontal non-sticky 
lines and the water surface. We observed a range of 1 to 16 vertical 
sticky lines per horizontal line, averaging 6 per line (n = 30 horizontal 
lines). The spacing between the sticky lines along the horizontal line 
varied from 11 mm to 25 mm, averaging 23 mm (n = 16 horizontal 
lines), giving the whole web the appearance of several sparse combs 
perpendicular to the water surface. The ends of the sticky lines not 
attached to the horizontal lines terminated at the water surface, 
extending neither along the water surface nor below it to any solid 
object. 
Sticky line-water junctions. Several experiments and observations 
support our observations that the lower ends of the sticky lines 
terminate at the surface film of the moving stream. 
1. Any probe, such as a stick or pencil, may be moved between, 
under, and completely around the point of attachment of the 
sticky line to the water surface without engaging or disturbing the 
sticky line. This shows that none of the sticky lines extends below 
the water surface, that there is no bottom horizontal line that 
connects the ends of the vertical sticky lines, and that the sticky 
lines do not extend upstream or downstream for any appreciable 
distance from their point of attachment with the stream. 
2. The probe can be moved to within 2 or 3 mm of the thread- 
water junction without snagging it, althought if it approaches too 
closely on the water film, the attachment point of the silk will slide 
toward the probe as one would expect of two free objects floating 
and juxtaposed on a water film. Therefore, the movement of the 
attachment point is not restricted. 
3. If a wettable but non-porous surface, such as a leaf, is first 
submerged in the stream, and then slowly brought up from under 
the surface to intersect the sticky line attachment point, and then 
completely out of the stream, the sticky line will come away with 
the water film on the leaf behaving in every way as if it was still 
attached to the stream surface. If wet leaf is then re-submerged in 
the stream, as soon as the water film on the leaf becomes 
continuous with the stream surface film, the attachment point will 
slide off the leaf and resume its former position directly beneath 
the horizontal line to which it is attached. 
These observations imply that even when the sticky line is attached to 
