1986 ] Opell — Web-monitoring by Miagrammopes 173 
to a frame’s East and South sectors and that, when moss-covered, 
the twig attached to this sector would be favored over the opposite 
moss-covered twig as a web-monitoring site. 
Discussion 
This species’ preference for moss as a web-monitoring site en- 
hances its protective resemblance. The exposed first legs of these 
green species have a tuft of green tibial setae that look like the small 
phyllidia of an extending moss plant (Fig. 1). Although these setal 
tufts are found in brown Miagrammopes species, they are more 
prominent in green species, where they become disproportionately 
larger in subadult and adult individuals. During the night Miagram- 
mopes often abandon their typical day-time position adjacent to a 
twig and hang on the monitoring line a centimeter or more from its 
attachment point to a twig. 
Choice of a web-monitoring site by Miagrammopes is facilitated 
by the fact that most of their simple, irregular webs have no single 
attachment point from which they must be monitored. A few webs 
have a particular thread that probably serves as an optimal monitor- 
ing line by virtue of its single attachment point to several diverging 
lines. However, most newly constructed Miagrammopes webs con- 
sist of an approximately horizontal thread with one or several inde- 
pendently diverging vertical or diagonal threads. Either end of this 
horizontal thread could serve as a monitoring site. I have seen dis- 
turbed Miagrammopes run to the opposite end of their horizontal 
threads and begin monitoring their webs from this new position. 
The greater number of missing individuals noted in the forest 
than in the enclosure experiments probably resulted from a higher 
rate of spiders ballooning from the forest frames. Three factors 
suggest that this difference is not due to predators removing spiders 
that chose bare twigs as web-monitoring sites. First, release and 
observation times were chosen so that most of site selection and web 
construction took place at night when threats from visually hunting 
predators were lowest. Second, during this study, no predatory 
insects were seen on the experimental frames or their supporting 
lines. Third, none of the spiders in the predator-free enclosure chose 
bare twigs as web-monitoring sites. 
This study does not address the mechanism by which individuals 
select moss-covered twigs. Experimental studies on cryptic insects 
