On the occurrence of a highly localized outbreak of a saturniid in lowland east Ecuador: a case study and literature review

For decades, outbreaks of insect herbivores in tropical forests were considered unusual or rare events primarily because of high plant diversity and the top-down impact of enemies. An alternative explanation is that these outbreaks are common but occur on sparsely distributed hosts high in the canopy and at scales of one or a few individual trees. Here, we report an outbreak of a saturniid in the genus Citioica Travassos & Noronha near the Amazon Basin of Ecuador on a single tree of Inga edulis Mart. The outbreak caused near complete defoliation (>90% leaf loss) and did not occur on nearby conspecifics. This is only the twenty-third documented case of a saturniid outbreak, of which more than 60% occurred in tropical habitats. This is the first report of an outbreak on a single tree. Members of the local indigenous communities are well aware of these Citioica outbreaks and collect these caterpillars for food whenever outbreaks are detected, suggesting that these isolated outbreaks are fairly common. Further research is required to explore the possibility that insect outbreaks in tropical forests may be more common than previously suspected but occur over very small spatial scales undetected high in the forest canopy.