Specialization of Atlantic rain forest twig-girdler beetles (Cerambycidae: Lamiinae: Onciderini): variation in host-plant use by microhabitat specialists

Most herbivorous insects show strong fidelity to specific resource types, and specialization may vary substantially between feeding guilds. However, one insect guild comparatively less studied in this regard is represented by stem-borers, in particular, twig-girdler beetles (Lamiinae: Onciderini). We evaluated the microhabitat specialization and host-plant utilization of adult Onciderini of a tropical rain forest for four consecutive years. The results showed that seven of the Onciderini species were microhabitat specialists and plant family specialist beetles appeared to be more specific to their microhabitats than generalist species. In addition, host-utilization varied among twig-girdlers, and smaller Onciderini species removed shorter and slender branches, whereas larger species girdled larger twigs. Girdling effort in large-sized beetles was higher than for smaller species. Thus, only few twigs are girdled by larger females in their lifetime. Females of O. saga, O. dejeani and O. ulcerosa sometimes interrupted the girdling process for up to 20 days when using plants with toxic compounds or in the presence of plant mutualistic ants. These findings suggest that microhabitat selection by Onciderini females is essential to find suitable food sources. In addition, factors other than girdling effort, such as competition or the low availability of host-plants, could be influencing egg laying on suboptimal hosts.