Between August to November (2018) and February to May (2019), 8 insect collections were made across three-grain crops—corn, wheat, and barley—at El Capulín, Salvatierra, Gto., totaling 6,596 specimens. The insect fauna included 11 orders and 59 families, of which 53 families are found in corn, 25 in wheat, and 24 in barley. The entomofauna was classified into two main functional groups based on their ecological roles and diets: 1) EFGs (ecological functional groups), which include predators, herbivores, parasitoids, vectors, decomposers, pollinators, and generalists; and 2) TFGs (trophic functional guilds), including phytophages, insectivores, decomposers, polyphages, necrophages, hematophages, carnivores, nectarivores, and mycophages. Principal component analysis of the EFGs showed that herbivores and predators dominated corn, while wheat and barley showed a more balanced distribution. Similarly, the phytophagous and insectivorous TFGs followed a similar trend. In maize cultivation, both trophic relationships and functional were shaped by antagonistic groups of predators and plant hosts, while in barley and wheat, more generalist groups were non-specific and prevailed. This suggests that corn favors the insect's dominance adapted to its developmental cycles, with abundance associated with demographic factors typical of phytophagous species and fewer families of other groups. Agronomic practices and ecological interactions in agroecosystems play important roles in shaping the composition of functional groups in the insect communities in the studied grain crops.
