The Impact of Construct Building by Caterpillars on Arthropod Colonists in a World of Climate Change

Construct (“shelter”)-building caterpillars are those that build structures on or in plants. When these constructs are colonized by other arthropods, the caterpillars act as ecosystem engineers. Here we describe the known and predicted impacts of caterpillars on their associated arthropod faunas, and how such impacts might change with increasing influence of humans on the global ecosystem. First, we provide evidence that the presence of constructs built by caterpillars influences community composition of arthropods on plants, encourages the initial invasion and abundance of exotic arthropod species, and influences the amount of damage inflicted on the plant. Second, we describe a qualitative model of the influence of construct traits (openness, presence of frass, and volume) on colonization by other arthropods. We predict that constructs with one or more openings, those that contain frass, and those with larger internal volumes will attract more colonists. Third, available data suggest increasing drought and temperature will reduce the abundance of constructs and increase the use of those constructs by predators, while increasing rainfall and higher predation will increase the use of constructs by herbivorous insects. Altogether, studies are needed that quantify current environmental impacts on both construct building by caterpillars and the use of those constructs by other arthropods. Such studies will necessitate a tritrophic approach, i.e., understanding the role of host plant variation, the responses of caterpillars and associated arthropods to each other and to the host plant, and the role of natural enemies in shaping the use of caterpillar constructs.