A tropical arthropod unravels local and global environmental dependence of seasonal temperature-size response.

In most ectotherms, adult body size decreases with warming, the so-called 'temperature-size rule' (TSR). However, the extent to which the strength of the TSR varies naturally within species is little known, and the significance of this phenomenon for tropical biota has been largely neglected. Here, we show that the adult body mass of the soil mite Rostrozetes ovulum declined as maximum temperature increased over seasons in a central Amazonian rainforest. Further, per cent decline per °C was fourfold higher in riparian than in upland forests, possibly reflecting differences in oxygen and/or resource supply. Adding our results to a global dataset revealed that, across terrestrial arthropods, the seasonal TSR is generally stronger in hotter environments. Our study suggests that size thermal dependence varies predictably with the environment both locally and globally.

A Simulation Model of the Mass Rearing of Tetranychus urticae Koch (Acari: Tetranychidae) on Beans.

The supply of predatory mites as natural enemies is a key component to guarantee the success of biological pest control programs as alternatives to chemical control in commercial crops. To meet the demand for a supply of biologicals, the mass rearing of natural enemies is an option, and the first step must be to develop a standardized system that maximizes the production of prey. One choice for this first step is to use simulation models that can evaluate scenarios that are difficult or complex to address experimentally. In this work, a model was developed to evaluate the current management conditions for the mass rearing of the pest mite Tetranychus urticae Koch. Our aim was to identify alternative scenarios to maximize mite production through mass rearing that could be evaluated in real systems. We assumed that populations of T. urticae were regulated by the conditions of supply-demand theory and modeled the age structure, temperature effects, and individual phenology of T. urticae. The supply-demand theory of resources was used to regulate populations, which involved structured ages and temperature effects for the different stages in the development of individuals. We used the functional response and the paradigm of metabolic pool models to describe resource acquisition and allocation. We demonstrated that 7- to 14-day-old plants infested with 45 or 62 T. urticae/plant could reach 25,000 individuals/plant, being 50% of these preys at the preferred stages by the predator Phytoseiulus persimilis Athias-Henriot. Our theoretical model requires validation in experimental/real systems of mass rearing to better verify the validity of all of the parameters and predictions before commercial implementation.