The impact of wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), on the photosynthetic capacity and primary metabolism of wheat, Triticum aestivum L., was evaluated in three different environments: environmental growth chamber, greenhouse, and field. C. cinctus elicited different photosynthetic responses in different environments. Wheat gas exchange parameters, such as photosynthesis, stomatal conductance, intercellular CO₂, and transpiration in the growth chamber environment were negatively affected by C. cinctus feeding. Conversely, the same gas exchange responses were not observed under greenhouse and field conditions. This study shows the important role of environmental variables, such as ambient CO₂ concentrations and light intensity, on plant responses to herbivores.