Contribution of Omnidirectional Flight Traps to Assess the Ant (Hymenoptera: Formicidae) Diversity in an Agroforestry System

Abstract

The Malaise trap is widely used for monitoring the diversity of flying insects. The omnidirectional model (Omnidirectional flight trap) is well known when hung in the understory, where it divides the sampling of these insects into two interception strata, a lower and an upper one. In general, the interest in using this trap type is because it allows to collect organisms with distinct flight behaviors to be discriminated against. Here, we investigated what information this trap can provide from samples of canopy ants and winged individuals as workers. We evaluated the sampling efficiency of the ant fauna, comparing the collection strata of this trap in a cocoa agroforestry system. To collect the ants, 40 traps were installed near an equivalent number of shading trees in a cacao plantation. A total of 374 specimens of ants belonging to 94 species or morphospecies of Formicidae were captured. Of these, 44 species were represented by alates of both sexes, while workers represented 68 species. A significant difference in the average number of ant species, both winged individuals and workers, was observed according to the trap interception stratum. A greater number of alates were collected in the upper stratum than in the lower one. An inverse pattern was observed for workers. However, we do not observe any difference according to the trap interception stratum when focusing on the whole ant diversity independently from their cast. On the contrary, the pattern of species composition comparing the two trap interception strata varied according to the ant casts. The Malaise traps are also interesting because they provide valuable information about the activity of canopy ants, such as foraging (workers) and mating flight (alates: height, orientation, time, according to the schedule of trap use).