174 
Psyche 
[Vol. 93 
show that two methods may be used in selecting a matching back- 
ground. Gillis (1982) showed that in one grasshopper species indi- 
viduals select backgrounds whose color matches that of their 
circumocular regions. By contrast, Sargent (1968) found that back- 
ground selection in some moths was hereditary and was unaffected 
by painting their circumocular scales. Color vision has not been 
demonstrated in Miagrammopes. However, the eyes of the species 
used in this study are well developed and have low f-numbers, indi- 
cating that they are effective in low light intensities (Opell and Cush- 
ing, in press). Tactile or moisture properties of the moss may also be 
important cues for its choice as a web-monitoring site. Unlike 
striped moths that must assume the proper orientation in order to 
take full advantage of their cryptic markings (Sargent 1969), the 
webs of Miagrammopes assure that they will assume the proper 
attitude after they have selected the correct background. 
Summary 
Members of the spider genus Miagrammopes construct simple 
capture webs consisting of only a few threads and assume a stick- 
like posture as they actively monitor these webs. A green Costa 
Rican species showed a statistically significant preference for moss- 
covered twigs as web-monitoring sites. This choice was observed in 
both a forest setting and a screened enclosure, and occurred on 
experimental frames which required spiders to attach their webs to 
both bare and moss-covered twigs. 
Acknowledgements 
I am grateful to the Organization for Tropical Studies for permit- 
ting me to use its facilities and to David and Deborah Clark, co- 
directors of the organization’s La Selva research station, for their 
help. This study was supported by National Science Foundation 
grant BSR-8407979 to the author. 
References 
Blanke, R. 
1972. Untersuchungen zur Okophysiologie und Okethologie von Cyrto- 
phora citricola Forskal (Araneae, Araneidae) in Andalusien. Forma et 
Functio, 5: 125-206. 
