How to avoid becoming a prey: Predatory encounters between an orb-weaving spider,Araneus pinguis (Karsch) (Araneae: Araneidae) and flying insects |
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Authors: | Tomoji Endo |
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Institution: | (1) Institute of Applied Zoology, Faculty of Agriculture, Hokkaido University, 060 Sapporo, Japan |
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Abstract: | Insects flying into the web of an orb-weaving spiderAraneus pinguis (Karsch) and their avoidance of (pre-hitting process) and escapes from (post-hitting process) the web were examined by direct
observation under natural and semi-natural conditions. In the pre-hitting process, mobile insects such as Brachycera, Lepidoptera
and Hymenoptera showed a low hitting ratio (number of insects hitting/number of insects flying within 1 m3 space around the web-site) because of active web avoidance and flying activity in layers lower or higher than those in which
the webs are usually laid. In contrast, less mobile insects like Heteroptera, Coleoptera and Homoptera showed a high hitting
ratio. In the post-hitting process, Brachycera, Lepidoptera and some Nematocera frequently escaped without being detained
by the web. Many Orthoptera and Hymenoptera escaped without any sign of detection by the spider. Coleoptera frequently escaped
during the spider's attack. Small insects from the Homoptera, Nematocera and Hymenoptera rarely escaped from the web, but
were not immediately attacked. Mean escape time of insects was correlated significantly with capture success of the spider.
Overall most of the escapes occurred in the early phases of the predation process. This indicates that escapes are unlikely
to result in heavy loss of time and energy expenditure due to unsuccessful predation. Escape patterns of insects seem to be
related to their mobility. |
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Keywords: | Anti-predatory behavior Araneus pinguis Capture success Flying insects Prey selection |
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