The phorid fly and the leaf - cutter ant by Maeve Higgins on Prezi
PDF | The leaf-cutting ants Atta sexdens (Linnaeus) and Atta laevigata (Smith) were parasitized by the following phorid flies: Apocephalus attophilus Borgmeier, Apocephalus vicosae cutting ants, gives rise to questions having to do with the . (Diptera, Phoridae) in relationship to its host, the leaf-cutting. In general, there are two types of associations between phorid flies and ants ants, leaf-cutter ants (Atta and Acromyrmex spp.) actions have assumed that co -occurrence of the ants and flies implies a host-parasite relationship. to these problems: mean number of ant species per fly species for Acanthophorides should. A compilation of leaf-cutter phorid species with their known and/or This review will summarize the current information about this system and will identify key questions . Apocephalus flies attack both ant genera with 8 recorded species .. ant activity/trial, and number of trails, then a positive relationship.
Behavioral patterns as well as specific features of these ant-parasitoid interactions are described, and their ecological importance discussed. Introduction Any successful endoparasitoid must overcome a hierarchical set of barriers in order to oviposit in a host.
The parasitoid must locate and encounter its prey, and, upon doing so, manage to insert an egg while overcoming the host's physical and behavioral defenses Vinson ; Godfray Several aspects of the behavior of parasitoids can affect the response of the hosts, making the defensive response of the hosts more or less effective in preventing the parasitoid from leaving offspring.
Behavioral Strategies of Phorid Parasitoids and Responses of Their Hosts, the Leaf-Cutting Ants
In general, behavioral mechanisms of hosts against parasites are the first line of defense Kenneth For dipteran parasitoids with mobile adult hosts, behavioral defenses are a critical element to overcome, and one that effectively determines the host range of these flies Feener and Brown Acromyrmex and Atta cut plant tissue from surrounding vegetation and carry the pieces back to their nest using a persistent trail network Kost et al.
When ant workers are outside the nest for any reason, they could be attacked by phorid Diptera: Phoridae endoparasitoids, which use a piercing ovipositor to insert an egg inside the worker's body. The phorid species that use Atta as hosts do not use Acromyrmex ants Elizalde and Folgarait The host-related behaviors i. Moreover, no generalizations have been made for any of these parasitoids in terms of host-related behaviors. Phorid species that frequently parasitize leafcutting ants belong mainly to three genera: Apocephalus BrownEibesfeldtphora recently raised to the genus status, being previously a subgenus of Neodohrniphora, Disney et al.
For example, one Eibesfeldtphora species attacked more often when ant foraging activity was higher Tonhasca Some of these behaviors can involve ants that are not directly at risk of being parasitized by phorids, in which case they constitute colony level responses against the parasitoids. One of these colony level behaviors against the phorids, and unique to leaf-cutting ants, is the presence of hitchhikers.
Hitchhikers are small workers, too small to host the phorids, that ride on the leaves transported by bigger and suitable host workers Eibl-Eibesfeldt ; Feener and Moss Through experimental and detailed observations in the field, Feener and Moss showed that hitchhikers had a defensive function against phorids that land on leaves to oviposit. Almost nothing is known about the behaviors that Acromyrmex ant species exhibit against the phorids that attack them, except for some occasional observations Brown Specifically, the following aspects of parasitoid behaviors were addressed: Then, focusing on host behaviors, the following characteristics were evaluated: Materials and Methods Host-related behaviors of phorids In order to describe host-related behaviors of phorids attacking leaf-cutting ants, the following were considered: Data was collected in 12 localities in Argentina and two in Paraguay sampling sites in Elizalde and Folgarait At each locality, and in at least three nests of each leaf-cutting ant species present, phorids were searched for in the sites where they are known to oviposit, such as foraging trails and cutting sites.
In addition, phorids were searched for at external refuse piles, where some ant species dispose of their wastes i. Once a phorid was found, its behavior was observed focusing on items bcand das mentioned above. Observations of phorids from a very short distance by a trained, naked eye were more efficient for behavioral data gathering than using a video camera because video-recording in the field at the speed and distances these small phorids move was not possible.
After completing the behavioral observation, phorids were captured in order to identify them to species. For completeness, unpublished data about the host-related behavior of a phorid species collected in La Selva Biological Station in Costa Rica were included.
The behavioral observations were all performed during daylight hours and when ant activity was well established. In this locality, the leaf-cutting ants present were Atta vollenweideri Forel and seven species of Acromyrmex Ac. Based on previous observations, and on those of Feener and Brownfour host-related behaviors displayed by phorids were defined, and were the main activities performed: When a phorid female was found attacking a host, her behavior was described verbally by the observer and registered using an audiocassette recorder until at least three oviposition attempts were made on different workers.
Recording observations in audiocassettes allowed quantifying the duration of each behavior. Following the observation period, the phorid was captured, and kept in a vial with alcohol, which was adequately labeled for later identification and to associate the phorid with the registered behaviors. The behavior of phorids while attacking ants was quantified for a total of 20 hours, for eight different species.
Differences among phorid species in the percentage of time allocated to each of the mentioned behaviors was compared with Kruskal-Wallis analyses of variance since the data could not be normalized for most behaviors, even after transformations. Differences among phorid species behaviors were determined using non-parametric tests, and P-levels were adjusted using Holm's correction Quinn and Keough One way or another, the leaf fragments find themselves on the forest floor being carried by the media workers.
Our research shows the average size leaf fragment to be about 0. Thus, each worker ends up carrying a weight about 3 times its own body weight, a far cry from the 50x weight differential heralded by popular television shows about the ants of course there is a difference between what the ants CAN and DO carry. It's not only leaves that are cut and carried; flower petals and bits of stems may be brought to the nest as well below Larger fragments may be carried by teams of workers; and there may be some confusion when they reach the nest with a piece too big to fit.
It's not unusual to see one or more minima workers riding on the fragments as they move to the nest.
Behavioral Strategies of Phorid Parasitoids and Responses of Their Hosts, the Leaf-Cutting Ants
Other sources, however, such as this onesuggest that the flies lay their eggs directly on the workers. The minima would be too small to support a parasitoid, so they are not vulnerable themselves and are free to chase away the parasitic flies.Brain-Eating Fly turns Victims into Zombies
In addition, the minimas are getting a head start on their job of raising fungus on the leaves; at this stage they are cleaning off any potential competing fungal spores so they don't get into the nest.
This image shows the foraging workers of all 3 subcastes.
The ants try to keep their main trails clean. This facilitates the movement of workers with the leaves. In extreme cases, they can wear a groove into the soil; the "superhighway" above was found near a large nest and was several inches wide and deep - and situated in such a way to suggest it was created by the ants themselves, not by another agent such as water. Below, a "logjam" created by an obstacle in the trail near the beach at Cahuita National Park.
Leafcutter Ants - Marietta College
Back at the Nest Of course, the purpose behind all the leafcutting is to transport the leaves back to the nest where they can become food for the fungi. From these low mounds trails radiate out in several directions; the trails may extend for hundreds of meters. A large nest can have thousands of chambers, some of these may be a foot or so in diameter.
Some chambers are used for brood, others for the fungal gardens more on those in a minuteand, in some species, there are chambers used for trash. This tremendous churning of the soil - bringing soil to the surface and taking vast quantities of organic material underground, no doubt has huge implications for the fertility of the soil. The colony also has hundreds of entrances, no doubt to help control the climate within.
The colony above from La Suerte is almost certainly Atta cephalotes as ants gathered there key out to that species. The colony to the left, at La Selva, on the edge of a clearing, may be A. Why is there any vegetation near the nest? Scientists are divided on this point. In some cases, the ants may bypass nearby plants because they don't meet the nutritional needs of the fungus.
More likely, certain plants may produce substances toxic to the ants or the fungi obviously the ants not only need to know what will kill them, but what will kill the fungi as well. Plants with higher concentrations of such chemicals will be skipped. Since some plants raise the amount of these defensive chemicals once they are attacked, it may be that the ants will partially defoliate a plant, stop feeding on it as it responds with increased defensive chemicals, and return to it later after it has "forgotten" the attack and the concentration of defensive chemicals is lowered.
Do the ants avoid certain plants so as not to kill all the food within easy reach and thus allow certain plants to recover? In the nest, the relative importance of the size of the different worker castes undergoes a dramatic shift. On the outside, it is crucial that a worker be big enough to cut and carry the leaves. Inside the nest, smaller size is the important thing.
These jobs largely fall to the minima, the smallest of the workers, whose head capsules may be less than 1mm wide. The large workers to the right are medias; the smaller workers minimas. It seems that under the ants' care the fungus has no need for the fruiting structures such as mushrooms that most fungi use and which most mycologists use to classify the fungi.
Grown by the ants, the fungus takes on a peculiar shape with enlarged structures full of nutrients that the ants can bite off and consume. The minima workers ensure that the fungus is placed on newly arrived leaf bits; add their own feces as a fertilizer recycling it in the process - smart!
It turns out that the story does not end here. Another fungus, Escovopsis, can invade the nest and overgrow the fungus that the ants are growing.
This second fungus is not good for the ants to eat, and the colony could die if it is not controlled. It turns out that in addition to the fungi, the ants "grow" another organisms - a species of the bacterium Streptomyces. Streptomyces are common in the soil, and most of them produce potent antibiotics to kill their competitors. The Streptomyces in the ant nests is no exception, and the workers apparently use the excretions from the bacteria to kill any of the invading fungus that escapes the normal housekeeping of the ants.
Certain areas of the ant worker's bodies have been found to be be modified, presumably to enhance the growth of the Streptomyces, and in fact the Streptomyces has been cultured from those patches on the ants. Thus, the leafcutters are not only fungal "farmers", but sophisticated pharmacists as well, producing and using antibiotics.
And we though we were smart! Any close association between two species is called a symbiosis particularly so when one species cannot live without the other. The association between the ants and their gardened fungi has long been held out as a prime example of a mutualistic symbiosis.
On the other hand, the Streptomyces seems to be another, third member of the mutualistic symbiosis with the ant and the fungus since all three of these species benefit from the association.
These 3 articles discuss this symbiosis: You might wonder - how does the fungus get to the nest in the first place? It turns out that when a queen ant leaves the nest where she was born she takes a bit of the fungus with her.
She even has a special pouch near her mouth to carry it. After mating, she removes her wings and digs a hole down into the ground; at the base of the hole she excavates a nest cavity.
She never goes above ground again. She lays some eggs and begins to rear young. She also removes the fungus and grows it by feeding it her feces. The young she raises by feeding them unfertilized eggs; she gets the resources to produce these eggs by breaking down the large flight muscles she no longer needs. She regulates the size of her developing young by feeding them carefully; the more she feeds them the larger they get, and she is aiming for nothing larger than the media with the 1.
These are the smallest workers that can go out and cut leaves. Once her first workers reach adulthood, they open up the nest and begin foraging; inside the nest they take over care of the fungi and the remaining young.
Psyche: A Journal of Entomology
The queen's duties are now relegated to laying eggs. The other big activity in the nest is the rearing of new ants. Again, this is a task left largely to the smaller workers. They tend to the young, first moving the eggs from place to place, later moving and feeding the larvae, and finally moving the pupae as needed the pupae, unlike many hymenopterans, are not encased in a silk cocoon.
The young ants also have to be groomed to eliminate parasites such as mites and other problematic organisms such as disease-causing fungi. The small minimas are well-suited to these tasks. In the figure to the right, you can see a number of media workers, some minimas, and a number of immature ants recognizable by their pale whitish appearance. Among the young are grub-like larvae and the pupae.