Effect of temperature on the survival of two stingless bee species (Hymenoptera: Meliponini) from northern Argentina

Stingless bees (Hymenoptera: Meliponini) are small-bodied, widely distributed in tropical regions, and efficient pollinators of native flora; however, they are particularly vulnerable to thermal stress, which can reduce their survival. In Argentina, few studies have examined the response of native species to extreme temperatures, so this work addresses the question: how does rising temperature affect Argentina’s stingless bees? We collected 40 forager workers of Scaptotrigona jujuyensis and 40 of Tetragonisca fiebrigi, which were subjected to three heating methods to evaluate methodological effects: a laboratory drying oven (heating rate, HR ≈ 1.4 °C/min), a laboratory hot plate (HR ≈ 4.5 °C/min), and a water bath (HR ≈ 2.5 °C/min). For each species, 10 individuals served as controls and 10 were assigned to each heating method. Before each trial, bees remained for 20 min under laboratory conditions (≈24 °C). We recorded the time until collapse (exposure time) and the temperature at collapse (critical temperature, CT), defined as the onset of uncontrollable muscle spasms. Mean CT values were compared between species using Welch and Wilcoxon tests, methodological effects were evaluated using one-way ANOVA, and survival curves were constructed as functions of exposure time and temperature. Preliminary results showed that S. jujuyensis had a significantly higher CT than T. fiebrigi (50.49 ± 5.67 °C vs. 45.70 ± 7.38 °C; Welch: t = 2.64, p = 0.011; Wilcoxon: W = 480.5, p = 0.021). Heating methodology also significantly affected CT (ANOVA: F = 36.96, p < 0.001). Survival curves indicated greater resistance of S. jujuyensis to increased exposure time and temperature. These preliminary findings indicate interspecific differences in physiological thermal tolerance and highlight the importance of considering heating methodology when estimating CT. Further experiments with larger sample sizes are needed to validate these results and better understand the thermal responses of Argentina’s stingless bees.