The South American Cactus Moth

Abstract

These individuals of Cactoblastis cactorum are from the Northeastern ecotype and were found feeding on this large Opuntia ficus-indica plant near Puerto Tirol, Chaco Province, Argentina. Photograph by Christopher Brooks. Cactoblastis cactorum individuals burrow into the stem segments of Opuntia species where they feed gregariously. These individuals from the Western ecotype have hollowed out this prickly pear cactus cladode near El Quebrachal, Salta Province, Argentina. Photograph by Christopher Brooks. The South American cactus moth is a well-known insect, both because it represents one of the most successful biocontrol releases known (in Australia), and because it has now become an escaped biocontrol agent that threatens the native prickly pear diversity in the United States and Mexico. We used collections of individuals from sites across the core of the species' native range (Argentina) and from known infestations in Australia, South Africa, and Florida to show that environmental niche models do not capture the fundamental determinants of habitat. Instead it seems likely that host traits are the driving force determining the quality and availability of habitat, both within and outside of the native range. Cactoblastis cactorum individuals collected from an Opuntia ficus-indica plant near Puerto Tirol, Chaco Province, Argentina. These individuals are curled up on some dessicant that is used for rearing in the laboratory so that the unrooted, damaged cactus pads do not become too wet for the larvae. Photograph by Christopher Brooks. These photographs illustrate the article “Native ecotypic variation and the role of host identity in the spread of an invasive herbivore, Cactoblastis cactorum” by Christopher P. Brooks, Gary N. Ervin, Laura Varone, and Guillermo A. Logarzo, tentatively scheduled to appear in Ecology 93(2), February 2012.