Reduction in the foraging activity of the leaf‐cutting ant Atta sexdens caused by the phorid Neodohrniphora sp.

Abstract

Females of the parasitic phorid Neodohrniphora sp. were collected in the field and released singly inside an observation chamber placed between a laboratory colony of Atta sexdens (L.) and its foraging arena. The number and speed of loaded and unloaded ants returning to the nest, the weight of foragers and their loads, the number of leaf fragments abandoned by ants, and the number of small workers ‘hitchhiking’ on leaf fragments were measured before phorids were released, while they were in the observation chamber, and after they were removed. Relatively few ants were attacked by Neodohrniphora sp., but the presence of flies prompted outbound ants to return to the nest and caused a significant reduction on the number and mass of foragers. Additionally, the weight of leaf fragments transported by ants was reduced and the number of abandoned fragments increased in response to Neodohrniphora sp. Presence of the parasitoid caused no significant changes in the number of hitchhiking ants. The regular ants' traffic was resumed after phorids were removed, but foraging activity remained below normal for up to three hours. In the field A. sexdens forages mostly at night, but colonies undergo periods of diurnal foraging during which ants are subject to parasitism from several species of phorid flies. Considering that daytime foraging may be necessary for nutritional or metabolical needs, phorids may have a significant impact on their hosts by altering their foraging behavior regardless of the numerical values 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)

“…In older colonies, A. sexdens foragers react to the presence of these flies by abandoning their loads and returning to the nest (Bragança et al 1998). Consequently, the occurrence of Neodohrniphora represents a disruptive factor in the foraging of Atta leaf-cutting ants.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 Tonhasca (1996), where it was incorrectly named Neodohrniphora declinata Borgmeier, and by Bragança et al (1998), where it was referred to as Neodohrniphora sp. No equivalent information is available for N. erthali.…”

“…Flies were taken to the laboratory and released individually inside an observation chamber placed between a 2.5-year-old A. laevigata nest and a foraging arena. Bragança et al (1998) described this experimental setting in detail. Fly's and ants' behavior was observed for 1h, then the fly was removed.…”

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).…”