Behavioral Ecology Advance Access first published online on February 13, 2008
This version published online on May 6, 2008
Behavioral Ecology, doi:10.1093/beheco/arm157
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Grouping increases visual detection risk by specialist parasitoids
Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA
Address correspondence to C. Low. E-mail: c_low{at}lifesci.ucsb.edu.
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Abstract |
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The benefits of prey grouping may be offset by increased detectability. With a focus on visual detectability, I investigated the potential costs of 2 traits, mine size and group size (number of mines per leaf), of a leaf-mining species, Antispila nysaefoliella (Lepidoptera: Heliozelidae), on the risk of visual detection by parasitoids and the ability to evade attack and capture after detection. Through field experimentation using artificial leaves and mines coated with a nontoxic adhesive spray for trapping insects, I found that the visual cues from groups of mines caused a significant increase in the number of parasitoids captured on experimental leaves (with artificial mines) relative to control leaves (without artificial mines). However, mine size did not. The observational evidence not only supports these patterns but also shows that the per capita risk of parasitism declines with large groups. These results provide evidence of a trade-off between avoiding visual detection and escaping attack after detection.
Key words: aggregation, conspicuousness, dilution effect, host-parasitoid, prey defense, vision.
Figure 1 and the funding paragraph have been updated.
Received 17 April 2007; revised 18 December 2007; accepted 20 December 2007.