Temperature Modulates Feeding Attributes, Assimilation of Nutrients and Rate of Development in Larvae of Mexican Beetles

The present study was designed to assess feeding attributes, assimilation of nutrients and development of larval stages of Parthenium beetle, Zygogramma bicolorata under different temperature conditions. Zygogramma bicolorata is an effective biocontrol agent of Parthenium weed. We hypothesized that at extreme temperatures (15°C/ 30°C), feeding attributes of larvae would be low due to thermal stress, and being large, fourth instars would display higher feeding attributes at all temparatures over the other instars. However, we found that when temperature increased from 15°C to 30°C, food consumption rates, assimilation of nutrients and developmental durations of larvae decreased, whereas their food utilization efficiencies increased. While larvae were more voracious and assimilated nutrients maximally at lower temperature (15°C), they utilized the food maximally and had short developmental durations at higher temperature (30°C). Further, third instars consumed and utilized the food maximally at extreme temperatures (15°C/30°C), while fourth instars did the same at optimum temperature (25°C). At all temperatures, fourth instars assimilated the nutrients maximally, followed by the third instars. Our study therefore indicate that fourth instars are more potent to exploit the weed at optimal temperature, while the third instars at the extreme temperatures.