PREY SELECTION BY THE NEOTROPICAL SPIDER 
ALPAIDA TV ON A BO 
WITH NOTES ON WEB-SITE TENACITY' 
By Todd E. Shelly 
Department of Biology 
University of California 
Los Angeles, CA 90024 
Introduction 
Prey selection by web-building spiders includes 2 principle com- 
ponents. First, webs may catch a nonrandom sample of the avail- 
able prey (passive selection). Among items caught in the web, the 
spider may then feed on preferred prey but reject unsuitable prey 
(active selection). As evident from a recent review (Riechert and 
Luczak 1982), quantitative field measurements of either component 
are relatively rare and particularly so for tropical species. 
Here I compare the web contents of Alpaida tuonabo (Chamber- 
lin and Ivie) with sticky trap samples of available prey. Field work 
was conducted at one site over a relatively short period of time thus 
reducing potential complications arising from habitat and seasonal 
differences in prey availability. As Olive (1980) and Uetz et al. 
(1978) found, however, prey availability may vary over short verti- 
cal distances, and to examine this possibility potential prey were 
sampled at several different heights. 
In addition, a second comparison was made between captured 
items being eaten and those left unattacked and uneaten. Since prey 
ignored during the day may have been consumed at night with the 
web, uneaten prey did not necessarily represent rejected prey. This 
comparison, however, does quantify the probability of immediate 
attack upon different types and sizes of captured prey. 
'While Araneus is the accepted generic designation, this species is not closely related 
to other members of this genus and should perhaps be placed in the genus Aplaida 
(H. Levi pers. comm.). 
Manuscript received by the editor December 20, 1982. 
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