PREY SELECTION IN AN ORB-WEAVING SPIDER: 
MICRATHENA GRACILIS { ARANEAE: ARANEIDAE)* 
By George W. Uetz and Scott P. Hartsock 
Dept, of Biological Sciences, 
University of Cincinnati, Cincinnati, OH 45221-0006 
Introduction 
A number of studies have examined the prey captured by web 
building spiders, and many have compared the captured prey with the 
insects available in the environment (Bilsing 1920; Turnbull 1960, 
1962; Cherrett 1964; Kajak 1965; Olive 1980; Nentwig 1980, 1983; 
Brown 1981; Shelly 1983, 1984; Robinson & Robinson 1970, 1973; 
Riechert & Tracy 1975; Uetz et al. 1978; Chacon & Eberhard 1980; 
Uetz & Biere 1980; Riechert & Cady 1984). The most common 
comparisons are between prey found in webs and the “potential prey” 
captured by traps that in some way mimic spider webs (sticky traps, 
windowpane traps, etc.). Although there is disagreement about what 
kind of trapping method most accurately assesses the prey actually 
available to spiders (see Uetz & Biere 1980; Chacon & Eberhard 1980; 
Shelly 1984), all these studies suggest, to a greater or lesser extent, 
that the range of prey taken by spiders demonstrates some degree of 
selectivity. Recent research has shown that specialization is the result 
of web placement, web structure, and behavioral choices in the attack 
process (Chacon & Eberhard 1977; Uetz & Biere 1980; Riechert & 
Luczak 1982; Nentwig 1983; Shelly 1983, 1984; Riechert & Cady 
1984; Craig 1986; Stowe 1986). 
An important question that many of these studies have addressed 
concerns the role of the spiders’ web in the selection of prey, and why 
some prey insects are trapped more or less efficiently than others. 
Most workers agree that the process by which insects fall prey to 
spiders in their webs is neither random nor passive because insects 
vary in their ability to avoid webs, or escape from them once caught 
(see Nentwig 1982; Craig 1986); and web design and function favor 
capture of specific prey types and sizes (see Riechert & Luczak 1982; 
Rypstra 1982; Stowe 1986). The capture of insects by spiders on the 
* Manuscript received by the editor October 26, 1986. 
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