1969] 
Sabath — Gea heptagon 
373 
7 m.. S of South Mills). They include 2 females, 2 juvenile 
females i male, 7 juvenile males of various sizes, and io small 
juveniles. The prolateral edge of the patella and tibia of the 
smallest juvenile measures a little over 0.6 mm, whereas that of the 
emerged spiderlings of the first eggsac average a little less than 0.5 
mm. Adults measure around 2. 5-3.0 mm. The smallest field juvenile 
is probably only one molt ahead of the emerged spiderlings. There- 
fore I assume that Gea normally emerge at this locality in the fall 
and presumably overwinter as juveniles. Another possibility, con- 
sidering the wide range of development found in field collections, is 
that at least more southern Gea produce more than one generation 
per year. 
Discussion 
Gea heptagon makes a vertical web in grass. As in species of 
Argiope , the spider rests in the center of the web, but no stabilimen- 
tum has been observed. Unlike Argiope , the spider readily drops 
out of the web when disturbed. Most unusual is the sudden change 
of color when dropping from the web. 
I have found reports of rapid color change in only four other 
spiders. Bristowe (1958, p. 264) observed the linyphiid Floronia 
bucculenta drop to the ground when disturbed and turn white 
abdominal areas to brown. He states that under the microscope 
white intestinal guanin cells contract rapidly to expose the brown 
body fluid when the spider is shaken; the cells take several minutes 
to expand again. He was told by N. L. Roberts in Australia of an 
araneid, Phonognatha wagneri , that reacts similarly. Uyemura 
( 1 957 ) reports color changes for the golden green tetragnathid 
Leucauge subgemma and the golden yellow theridiid Argyria venusta 
\_~Chrysso venusta]. In both “when picked [up] or shaken strongly 
[out of the web]” the color breaks up into numerous star-like flecks. 
As in the Gea heptagon observed, the spiders darken instantaneously 
but recovery to normal takes several minutes. 
Of interest also is the open sector occasionally found on the lower 
part of Geas web. Open sectors are found in the upper part of the 
web of Zygiella perhaps facilitating rapid descent from the retreat 
above it to the hub. The open sector in the web of Gea heptagon 
might also be an adaptation to the habit of dropping out of the 
web on disturbance. 
