Parasitic flies (Diptera: Phoridae) influence foraging rhythms and caste division of labor in the leaf-cutter ant, Atta cephalotes (Hymenoptera: Formicidae)

Abstract

Three lines of evidence, including interspecific comparisons, temporal division of foraging between size castes, and experimental manipulations, suggest that the diurnal parasitoid Neodohrniphora curvinervis (Diptera: Phoridae) influences both the caste sizes and numbers of leaf-cutter ants (Atta cephalotes) that leave their underground nests to collect leaves. At Parque Nacional Corcovado in Costa Rica, A. cephalotes was attacked by Neodohrniphora during the daytime, and foraged less during the day than at night; a closely related ant at the same site, A. colombica, had no phorid parasites and foraged exclusively during the day. Most daytime foragers of A. cephalotes were smaller than the lower size threshold for attack by Neodohrniphora, while nocturnal foragers, active when parasitoids were absent, were both larger than this threshold and within the energetically optimal size range for foraging. When I supplied artificial lighting to allow phorids to hunt at A. cephalotes colonies past dusk, ants foraged less than when light was provided but flies were removed. The influence of Neodohrniphora on the foraging activity of A. cephalotes may explain why investigations focusing on abiotic factors have largely failed to discover what drives this ant's daily foraging cycles, and suggests that forager sizes are influenced not only by energetic efficiency, but also by the threat of parasitism.

Combat between large derived societies: A subterranean army ant established as a predator of mature leaf-cutting ant colonies

“…While top-down regulation from parasitoid Phorid flies and the fungal pathogen Escovopsis may also be important (Orr, 1992;Braganca et al, 1998;Currie, 2001), possible regulation by predators has been given little attention. Rao (2000) attempted to address the relative importance of an army ant predator, armadillo prédation, and phorid fly parasitoids in regulating Atta populations, but unfortunately this study had a serious methodological problem.…”

Parasitism characteristics of two phorid fly species in relation to their host, the leaf-cutting ant Atta laevigata (Smith) (Hymenoptera: Formicidae)

“…Although the defensive behaviors of leaf-cutting ants are similar when foragers are threatened by Neodohrniphora spp. that parasitize their heads (Eibl-Eibesfeldt & Eibl-Eibesfeldt 1967, Orr 1992, Feener & Brown 1993, Tonhasca 1996, the response of A. laevigata…”

“…These flies pursue and attack the larger foragers walking along trails, but nearby ants are also disturbed by flies' attacking bouts. Neodohrniphora have been implicated in the diel shift of foraging activity exhibited by Atta cephalotes (L.) (Orr 1992, Feener & Brown 1993 and in the reduction of the forager force size of Atta sexdens (L.) (Bragança et al 1998, Tonhasca & Bragança 2000. When exposed to a Neodohrniphora species, young A. sexdens colonies (less than 1-year old) stop completely their foraging activity within five minutes of initial contact with the parasitoids (D.D.O.…”

“…Atta sexdens and Atta laevigata (Smith) are two of the most common leaf-cutting ants in Brazil, and both represent serious pests of agriculture and forestry (Fowler et al 1989 Orr 1992, Feener & Brown 1993, N. tonhascai attacks the head of the larger workers. Its behavior and parasitic characteristics in relation to A. sexdens have been investigated by Tonhasca (1996), where it was incorrectly named Neodohrniphora declinata Borgmeier, and by Bragança et al (1998), where it was referred to as Neodohrniphora sp.…”

Características biológicas e comportamentais de Neodohrniphora elongata Brown (Diptera, Phoridae), um parasitóide da saúva Atta sexdens rubropilosa Forel (Hymenoptera, Formicidae)

“…Embora causem baixos índices de parasitismo natural em saúvas (2 a 4%), os forídeos são capazes de alterar negativamente o comportamento de forrageamento de seus hospedeiros, principalmente pela diminuição do número e tamanho das forrageadoras ao longo das trilhas e da massa de fragmentos vegetais transportados para o ninho (Orr 1992;Bragança et al 1998;Tonhasca et al 2001). Esses parasitóides podem coexistir em uma mesma trilha de forrageamento de Atta spp., selecionando operárias de diferentes classes de tamanho para atacar e, consequentemente, podem ter um efeito combinado na redução do forrageamento (Tonhasca et al 2001;Bragança & Medeiros 2006).…”