Temperature modulates feeding attributes, biochemical assimilation of macronutrients and rate of development in larvae of Parthenium beetles

Abstract The present study assessed the feeding efficiency, macronutrient assimilation and larval development of the Parthenium beetle, Zygogramma bicolorata Pallister, a biocontrol agent for the invasive Parthenium weed, under varying temperature conditions. We hypothesized that deviations from the optimal temperature (~25°C) would impair larval feeding efficiency due to temperature‐induced stress. Our results revealed that both larval consumption and growth rates declined at temperatures below (15°C, 20°C) and above (30°C) the optimal temperature (25°C). In contrast, food conversion efficiency improved as temperatures increased from 15 to 30°C. Protein assimilation by larvae decreased across the temperature range, while glucose assimilation increased. Triglyceride assimilation initially decreased from 15 to 20°C/25°C but increased from 20°C/25°C to 30°C. As temperatures increased from 15 to 30°C, both the body size and developmental durations of larvae decreased. These findings suggest that Z. bicolorata larvae adopt different survival strategies depending on temperature conditions. At suboptimal temperatures, larvae grow larger, assimilate more proteins and triglycerides, but consume and utilize food more slowly. Conversely, at supraoptimal temperatures, larvae exhibit reduced body size and food consumption rates, but their food utilization efficiency improves, leading to faster development. Therefore, both low and high temperatures could limit the biocontrol efficiency of Z. bicolorata larvae in the Indian subcontinent.