Growth and survival of the superorganism: Ant colony macronutrient intake and investment

Insecticide resistance in social insects: assumptions, realities, and possibilities

Insecticide resistance is an evolved ability to survive insecticide exposure. Compared with nonsocial insects, eusocial insects have lower numbers of documented cases of resistance. Eusocial insects include beneficial and pest species that can be incidentally or purposely targeted with insecticides. The central goal of this review is to explore factors that either limit resistance or the ability to detect it in eusocial insects. We surveyed the literature and found that resistance has been documented in bees, but in other pest groups such as ants and termites, the evidence is more sparse. We suggest the path forward for better understanding eusocial resistance should include more tractable experimental models, comprehensive geographic sampling, and targeted testing of the impacts of social, symbiont, genetic, and ecological factors.

Temperature influences lipid content in the red harvester ant, Pogonomyrmex barbatus

Temperature is one of the most important environmental conditions affecting physiological processes in ectothermic organisms like ants. Yet, we often lack information on how certain physiological traits covary with temperature across time. Here, we test predictions on how one trait-lipid content-covaries with temperature using a conspicuous, ground-dwelling harvester ant. We focus on lipid content as fat bodies are metabolically active tissues that are important for storing and releasing energy in response to demand, which could be vital for survival under variable temperatures. From March to November, we extracted lipids from surface workers of 14 colonies while simultaneously recording ground temperature. We first assessed if lipid content was highest during cooler temperatures when ants were less active and less metabolically stressed. In doing so, we found that lipid content of ants declined almost 70% from cool months (November lipid content = 14.6%) to hot months (August lipid content = 4.6%). We next assessed if lipid levels from a group of ants collected at a single time point could change by placing individuals into environmental chambers set at 10, 20, and 30°C (i.e., the approximate span of average temperatures from March to November). Temperature again had a significant impact such that after 10 days, lipid content of ants in the hottest chamber (30°C) had decreased by more than 75%. While intraspecific variation in physiological traits often follows seasonal patterns, our results suggest fluctuations in temperature may account for a portion of the variance observed in traits like lipid content.