Geometrical Games between a Host and a Parasitoid

Avoiding detection by parasitoids is nearly impossible for most leafminers in their visually striking mines, and they often suffer from a high mortality rate by a great variety of parasitoid species. The leafminer-parasitoid interaction bears a strong resemblance to the princess-monster game developed in game theory, in which a "monster" (parasitoid) selects an optimal search strategy to capture the "princess" (leafminer), while the princess selects an optimal strategy to hide from the monster. This article attempts to illustrate and to quantify the additional complexity that occurs when the princess can modify the arena in which the monster searches. Feeding activity of the leafminer Phyllonorycter malella creates feeding windows, which are spots on the mine. Its main parasitoid Sympiesis sericeicornis is able to insert its ovipositor only through these feeding windows. Parasitism risk depends both on the leafminer-feeding pattern, which determines the structure of the arena in which the parasitoid searches, and on the position of the leafminer within the mine. The adaptive value of observed patterns of mine development and leafminer behavior is evaluated by comparing them to predictions from a simulation model of random patterns and leafminer positions. The leafminer creates a heterogeneous environment by leaving a central area of uneaten tissue. This area acts as a protecting shield and greatly diminishes the risk of parasitism. Hence, by controlling the structure of the arena in which the princess-monster game is played, the leafminer defines some of the rules of the game.