Burrowing in the bark or in the sapwood?

Bark beetle and ambrosia beetle (Curculionidae: Scolytidae and Platypodidae) burrow into wood and oviposit. Bark beetle burrows into inner bark and its larvae eat it, but ambrosia beetle burrow into sapwood and its larvae eat symbiotic fungi brought by the adult. In this seminar, we ask the evolution of wood utilization. An ovipositing female burrows in the inner bark and in the sapwood, and each of her offspring chooses which microhabitat to stay and to further utilize the wood, in which there is competition among siblings. We analyze the ESS strategy of the ratio of utilization between inner bark and sapwood. In the ESS, larvae often utilize only sapwood or only the inner bark. The condition for these two cases depends on the relative suitability of the two microhabitats, the intensity of competition, and the cost of ovipositon. key words: bark beetle, ambrosia beetle, symbiosis, evolutionary stable strategy