Behavioral Strategies of Phorid Parasitoids and Responses of Their Hosts, the Leaf-Cutting Ants
Leafcutter ants, a non-generic name, are any of 47 species of leaf-chewing ants belonging to Their societies are based on an ant-fungus mutualism, and different species of ants use different species When the ants are out collecting leaves, they are at risk of attack by some species of phorid flies, parasitoids that lay eggs. Symbiosis Research Project. Create Your This phorid fly and leaf - cutter ant I found in Central America and parts South America. This fly lays. Phorids that parasitize leaf-cutting ants affect the foraging activity of their hosts the ants; (2) flying: when the phorid was flying to get close to an ant, came back to the The relationships between the dependent variable (presence of against the ground, so that the tips were not accessible to the phorid.
Photo credit Halvard Hatlen, hosted wikicommons. With approximately 4, species known worldwide, most dwelling in tropical latitudes, these flies possess an incredible variety of life styles.
This latter group of phorids are extremely valuable to forensic entomologists. But as fascinating as these life styles are, it is those that consume ants heads from the inside that naturally I was most interested in. The brain-eaters Parasitoid phorid flies are the scourge of many ant species. As the ants forage outside their nests, phorids stalk their hosts, hovering above them menacingly.
The march is halted as the ants head falls off, decapitated by the secretion of neck-membrane dissolving enzymes produced by the developing fly. A grizzly but amazing lifecycle. Pseudacteon curvatus ovipositor used for injecting an egg into its ant hosts.
Thirty minutes after the last worker was marked, the number of marked workers in the first nest 1nests 2, 3, and 4and transporters nests 5 and 6 leaving the nest were counted every 30 min for 6 h.
To determine the number of heap workers workers entirely confined to the heap surface in each nest, three scan counts were taken in the morning and evening across 3 days giving a total of six counts per nest, per day.
For comparison, we determined the number of foragers for three nests nests 1, 5, and 6. We also measured the total length of foraging trails. The number of foragers present both laden and unladen was counted three times in three cm sections along each trail during a foraging activity peak.
We determined the mean number of foragers per cm section per trail and multiplied this number by the total trail length to estimate the total number of foragers. This is likely to be an underestimate of total forager number, as it only counts foragers on main trails. The number of laden foragers entering the nest was counted for 3 min hourly for 5 h during a foraging-activity peak.
Division of labor Nest 5 was selected to test the hypothesis that waste management is an alternative endpoint to foraging for workers outside the nest and that waste workers do not become foragers or vice versa.
Such a division of labor would prevent waste workers from contaminating leaf fragments entering the nest, which would occur if they became foragers. The methods used also allowed us to investigate the division of labor between waste transporters and heap workers.
In particular, we tested whether waste transporters become heap workers and vice versa. Do foragers ever become transporters or heap workers? Two groups of and foragers were paint-marked over a 3-day period on the pronotal spines of the thorax using carbody paint applied with a seeker. Group 2 workers were marked 6 weeks after group 1 and were also used in the recruitment experiment see below. The heap was observed for two min periods each morning and evening for a total of 20 days between 15 March and 3 April giving 40 observation periods.
Marked ants working as either transporters or heap workers were noted. Marked heap workers were removed. We also observed foraging trails to ensure that marked foragers were still alive. Do transporters become heap workers?
Two groups of and transporters were marked as above but with a second color. The heap was observed for two min periods each morning and evening for the following 20 days giving 40 observation periods. Any marked heap workers were removed. As above, we also observed the transporters to ensure that marked individuals were still alive.
Do heap workers become transporters? Seventy-six heap workers were marked over 4 days with a third color, and their presence or absence on the heap or transporting trails was observed daily for two min periods. Weights of workers To determine whether there was a size-based division of labor among foragers, waste transporters, and waste heap workers, we took 50 foragers, 50 transporters, and as many heap workers as could be collected from each of 13 nests and weighed them.
Transporter recruitment The group of marked foragers was also used to investigate whether foragers are recruited to waste management if the number of waste transporters is drastically reduced.
We counted the number of waste transporters per minute for 3 min every 30 min for 60 min as they emerged from the waste exit.
The phorid fly and the leaf - cutter ant by Maeve Higgins on Prezi
Then approximately transporters were removed over 60 min. We recorded the waste output rate and the presence of marked foragers among transporters over the next 3. The number of heap workers was also recorded. Waste-directed aggression Hart and Ratnieks showed that in laboratory colonies of Atta cephalotes, both foragers artificially contaminated with waste and waste heap workers were subject to heightened aggression from nest mates.
They proposed that this aggressive response to waste-contaminated ants helps prevent waste workers from leaving the heap and thereby contaminating the fungus gardens Hart and Ratnieks, We investigated whether similar aggression occurred in A.
First, we determined whether ants working with waste transporters and heap workers were subject to heightened aggression from nest mates. Taking the three forager groups, 25 foragers from the remaining forager stock were individually introduced to forager group 1.
Twenty-five workers from the transporter stock were similarly introduced to forager group 2. Finally, 25 workers from the heap worker stock were introduced to forager group 3.
We performed similar introductions for the three transporter and three heap worker groups, giving all possible combinations of resident worker group and introduced workers. For each introduction, any aggression, defined as resident ants biting the focal ant, was noted, and the focal ant was removed before the next introduction. This was repeated for five colonies. Second, to investigate the effect of waste contamination, a separate group of 25 foragers was housed for 3 h in a petri dish half-filled with waste and introduced, following the same procedure as above, to a group of 25 foragers.
Waste heap location We tested two hypotheses concerning how the juxtaposition of the waste heap and foraging trails can be adaptive in terms of colony hygiene. First, we hypothesized that heaps would be located downhill from forage entrances to prevent rain from washing waste back into the nest and that heaps could be closer to forage entrances when the colony was situated on a steep slope.
Second, we hypothesized that foraging trails do not pass close to heaps, to prevent foragers from becoming contaminated with waste. For colonies with a single forage entrance, we measured the shortest distance along the ground between the hole and the heap. Majors, the largest worker ants, act as soldiers, defending the nest from intruders, although recent evidence indicates majors participate in other activities, such as clearing the main foraging trails of large debris and carrying bulky items back to the nest.
Ant-fungus mutualism[ edit ] Their societies are based on an ant-fungus mutualismand different species of ants use different species of fungus, but all of the fungi the ants use are members of the family Lepiotaceae. The ants actively cultivate their fungus, feeding it with freshly cut plant material and keeping it free from pests and molds. This mutualistic relationship is further augmented by another symbiotic partner, a bacterium that grows on the ants and secretes chemicals; essentially, the ants use portable antimicrobials.
Leaf cutter ants are sensitive enough to adapt to the fungi's reaction to different plant material, apparently detecting chemical signals from the fungus. If a particular type of leaf is toxic to the fungus, the colony will no longer collect it.
Leaf-Cutter Ant Parasitoids: Current Knowledge
The only two other groups of insects to use fungus-based agriculture are ambrosia beetles and termites. The fungus cultivated by the adults is used to feed the ant larvae, and the adult ants feed on leaf sap. The fungus needs the ants to stay alive, and the larvae need the fungus to stay alive, so the mutualism is obligatory. The fungi used by the higher attine ants no longer produce spores. These ants fully domesticated their fungal partner 15 million years ago, a process that took 30 million years to complete.
Waste management is a key role for each colony's longevity.