Phorid parasitoids of the leaf‐cutting ant Atta laevigata in the Atlantic Forest: occurrence, parasitism rate, and host size

The leaf‐cutting ant Atta laevigata (Smith) (Hymenoptera: Formicidae, Attini) causes significant damage to agricultural crops and forest plantations. Conventional control strategies include the use of formicide bait, whose active ingredients pose environmental risks. Several flies of the family Phoridae (Diptera) have shown potential as biocontrol agents of leaf‐cutting ants. This study aimed to determine which phorid species parasitise A. laevigata in the Atlantic Forest, their parasitism rates, and host sizes. Phorids and ants were collected during 12 months from foraging trails and entrance holes of A. laevigata nests located in a natural forest of southeastern Brazil. Phorids collected in the field and those emerged from parasitised ants were identified at the species level. Parasitism rate was determined for each phorid species, the head width of parasitised ants was measured, and confidence intervals were calculated. Eibesfeldtphora erthali (Brown), Eibesfeldtphora bragancai (Brown), Eibesfeldtphora declinata (Bogmeier), Apocephalus vicosae Disney, Apocephalus attophilus Borgmeier, and Myrmosicarius grandicornis Borgmeier parasitised A. laevigata at an overall rate of (mean ± SE =) 5.9 ± 0.76%. Apocephalus spp. had the highest parasitism rate (2.8 ± 0.60%), followed by Eibesfeldtphora spp. (2.2 ± 0.77%), A. vicosae (0.23 ± 0.07%), and M. grandicornis (0.16 ± 0.12%). Large workers were mainly parasitised by E. erthali and A. attophilus, intermediate workers by A. vicosae and E. declinata, and small workers by E. bragancai and M. grandicornis. The phorid A. attophilus had the highest parasitism rate, the widest range of host sizes, and an even distribution of parasitism throughout the year. The high parasitism rates registered for some nests samples (>40%) highlights that ant parasitoid flies are important natural enemies in natural environments and that they possess a great potential to be used in biocontrol programmes. In natural environments, parasitic phorid flies (Diptera) are natural enemies of leaf‐cutting ants. Atta laevigata (Hymenoptera: Formicidae) causes significant damage to agricultural crops. Conventional control strategies include the use of formicide bait, but active ingredients pose environmental risks. Several phorid flies have shown potential as biocontrol agents of leaf‐cutting ants. This study aimed to determine which phorid species parasitize A. laevigata in the Atlantic Forest (Southeast Brazil), their parasitism rates, and host