Interactions between phytophagous insects and their Opuntia hosts

Abstract

Abstract. The cactophagous insect community on opuntias is analysed to show the number of insect species in different taxa. An extension of this analysis gives the average species complement on large and small opuntias. A highly significant positive correlation is found between the total number of phytophagous insect species on individual Opuntia species and a measure of the overall ‘architecture’ of their host plants. The specificity of the phytophagous insects on opuntias is briefly considered and the community as a whole analysed by guilds. The co‐evolution of the Opuntia‐feeding insects and their hosts has culminated in a community of specialist insects to the exclusion of nearly all generalist phytophages. The life history strategies of the Opuntia‐feeding insects are reviewed. Common to all developmental stages are morphological and behavioural adaptations that reduce the risk of attack by natural enemies. This is clearly the consequence of living on structurally simple host plants where there is little place to hide. The possible influence of insect herbivores on Opuntia evolution is discussed. An understanding of the interactions between the phytophagous insect community and opuntias has clear implications for the biological control of alien Opuntia weeds.