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Keywords:

  • Cassida rubiginosa;
  • multitrophic;
  • oviposition habitat selection;
  • Polistes dominulus;
  • predation

Summary

  • 1
    In heterogeneous environments, the risk of predation and parasitism for phytophagous insects varies among different microhabitats. Adult females can escape natural enemies by depositing their eggs on sites unfavourable for prey-searching predators or parasitoids. Host plant characteristics can determine the availability of such spatial refuges.
  • 2
    We assessed the importance of host plant exposure for the predation probability of shield beetle (Cassida rubiginosa Müller) larvae by paper wasps (Polistes dominulus christ), hypothesizing that prey on exposed (i.e. free-standing) plants are more likely to be found and eaten by predators than prey on hidden (i.e. surrounded by other vegetation) plants. Because larval predation is a major mortality factor in shield beetles, we further hypothesized that the prey would adapt and avoid high-risk plants for oviposition. Finally, we investigated the influence of egg parasitism on the prey's host plant choice.
  • 3
    Host plant exposure significantly affected predation probability of Shield Beetles. Larvae on hidden host plants were less likely to be killed by the wasps than larvae on exposed shoots. However, females did not prefer the low predation risk environment of hidden plants for oviposition. The rate of parasitism was equal on exposed and hidden plants, and thus probably does not contribute to the oviposition habitat selection of prey.
  • 4
    Our study shows experimentally that characteristics of the first trophic level (i.e. host plant exposure) can affect the foraging success of insect predators. Different reasons, potentially responsible for the apparent non-selective host plant choice in beetle females, are discussed.