ECOLOGICAL RELATIONSHIPS OF A GUILD OF TROPICAL BEETLES BREEDING IN CECROPIA PETIOLES IN COSTA-RICA

Petioles are not usually thought of as a habitat for wood-boring insec ts. The large, woody leaf petioles of Neotropical Cecropia trees, howe ver, have a diverse coleopterous fauna: 36 beetle species in three sub families of Cerambycidae and Curculionidae were recorded from Cecropia leafstalks in Costa Rica. A high percentage of the petioles were colo nized by beetles in many patches, though fewer were colonized in sun-e xposed sites. Community composition was dependent on forest type, peti ole moisture and geographical location, but not on the species of Cecr opia. Species of Scolytinae were most abundant though species of Zygop inae and Lamiinae were found regularly. The host-specific scolytine ge nus Scolytodes dominated in most localities, although species of Hypot henemus, Coccotrypes and Xylosandrus morigerus occurred frequently. Sy mpatric species of Scolytodes clearly used different parts of the peti oles. Brood sizes of scolytine beetles were extremely low, ranging fro m two to ten offspring on average. However, mortality due to parasitoi d wasps or predators was low, and since fresh leaves fall close to the previously fallen ones, mortality due to dispersal may also be low. T hus, large beetle populations can exist despite extremely low brood si zes.