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Effectiveness Of The Minima Caste Of The Leafcutter Ant (Atta Cephalotes) On Cleaning Harvested Leaves, December 2016, Tori Braun
Tropical Ecology and Conservation [Monteverde Institute]
Leafcutter ants have been practicing agriculture longer than humans themselves. Leafcutter ant species, Atta cephalotes, common to Central and South America, cultivate a unique fungus, Leucocoprinus gonogylophora, that sustains the lives of millions of leafcutter ants within a single colony. In order to be efficient farmers, A. cephalotes have developed a caste system consisting of a queen, soldiers, workers, and minima. Each caste has a specific role within the colony, however, the role of the minima is still highly debated among scientists. It is hypothesized that the minima clean the surface of the leaves collected from nearby plants on the …
Optimal Foraging In Leafcutter Ants (Atta Cephalotes) Selection Of Leaves Based On Proximity To The Nest, May 2011, Robert O. Snowden
Optimal Foraging In Leafcutter Ants (Atta Cephalotes) Selection Of Leaves Based On Proximity To The Nest, May 2011, Robert O. Snowden
Tropical Ecology and Conservation [Monteverde Institute]
The foraging tendencies of Atta cephalotes, a leaf-cutting ant, have been widely studied. Optimal foraging theory dictates that ants should maximize rate of energy intake while minimizing costs by harvesting from suitable food sources closer to the nest. However, actual foraging patterns are more disparate and do not always reflect optimal strategies. Here I measure harvesting rates and recruitment speeds at different distances from the nest of A. cephalotes colonies by offering six leaf disk samples every 15 minutes at 5, 10, and 15 meters from the nest entrance. Harvesting rate was significantly higher closer to the nest, with 54% …
Foraging Efficiency And Polymorphism Of The Submajor Caste In E. Burchellii, May 2011, Nathan A. Sellers
Foraging Efficiency And Polymorphism Of The Submajor Caste In E. Burchellii, May 2011, Nathan A. Sellers
Tropical Ecology and Conservation [Monteverde Institute]
Army ants are superefficient in their retrieval of prey. There are four distinct worker castes in Eciton burchellii each important to the high efficiency of foraging. When prey is too large for an individual it is segmented by workers into manageable pieces then conveyed to the bivouac. Workers carrying prey were collected to determine the relationship between prey size and the worker(s) carrying prey as well as examine prey as an evolutionary pressure for selection of the submajor caste. Results show length and width are poor determinants of which caste is performing the retrieval task, as all castes are equally …
Bridge Building And Foraging Efficiency In The Army Ant Eciton Burchellii, May 2011, Daniel Brunelle
Bridge Building And Foraging Efficiency In The Army Ant Eciton Burchellii, May 2011, Daniel Brunelle
Tropical Ecology and Conservation [Monteverde Institute]
Efficiency in food transport is vital for all organisms. Eusocial insects are efficient because of decentralized colony control, caste specialization, and unique behaviors. Bridge building in the army ant Eciton burchellii has been widely studied as a mechanism that augments prey transport efficiency. Little data exist on why bridges confer an advantage and how their dimensions facilitate rapid food delivery. It is also less well studied how efficiency on a bridge compares to the average efficiency of ant traffic on transport pathways that do not have ant bridges. Bridge lengths and widths were recorded and patterns were looked for between …
Leaf Area, Worker Size, And Number Of Hitchhiking Minima In Atta Cephalotes, November 2010, Daniel Shimek
Leaf Area, Worker Size, And Number Of Hitchhiking Minima In Atta Cephalotes, November 2010, Daniel Shimek
Tropical Ecology and Conservation [Monteverde Institute]
Several species of leaf-cutter ants, including Atta cephalotes, exhibit an interesting behavior of hitchhiking minima. Minima are the smallest of the polymorphic castes of leaf-cutter ants and the function and origin of this hitchhiking behavior is not completely understood. There are several hypotheses for this behavior, and the most popular include defense against parasites and cleaning the leaf fragment of contaminants. Studies have investigated some patterns of hitchhiking behavior including different frequencies during day and night and distance from colony. This study examined the relationship between head width, leaf area and the number of hitchhiking minima in A. cephalotes. Ants …
Müllerian Body Production By Cecropia Obtusifolia (Cecropiaceae) With And Without Azteca Ants, November 2010, Josh Neighbor
Müllerian Body Production By Cecropia Obtusifolia (Cecropiaceae) With And Without Azteca Ants, November 2010, Josh Neighbor
Tropical Ecology and Conservation [Monteverde Institute]
Cecropia obtusifolia (Cecropiaceae) has a facultative mutualism with Azteca ants to minimize herbivory. In this study, Müllerian Bodies (MBs), glycoprotein bodies the plant produces to feed its mutualist ants, were systematically removed, from C. obtusifolia. A second study tested at what rate the tree would decrease its production of MB if the ants were restricted from removing them. It was found that removal of the MBs did result in an increase in MB production for two of the five trees in the treatment group. The C. obtusifolia where the ants were restricted from removing the MB, in all but one …
Subcaste Composition In Responses To Alarm And Non-Alarm Pheromones On Foraging Trails Of Leaf-Cutter Ant Atta Cephalotes (Hymenoptera: Formicidae), November 2010, Michael Marquis
Tropical Ecology and Conservation [Monteverde Institute]
The response of the leaf-cutting ant Atta cephalotes to its alarm pheromones from crushed heads were compared to its response to crushed bodies without heads in order to examine the relative subcaste (minor and forager) composition of the responding individuals. The percentage of minor workers responding to the body parts near the foraging trail were recorded and compared with the experimentally determined percentage of minors in the trail traffic. The average percentage of minors in the ants responding to the two treatments (Heads: 44.9±0.72%, Bodies: 38.8±0.77%, N = 1300) both differed (p = .0007, p = .0113, df = 1) …
Differences In Atta Cephalotes Foraging Rate And Amount Of Substrate Harvested Following The Introduction Of An Antifungal Agent, November 2010, Benjamin Hedin
Differences In Atta Cephalotes Foraging Rate And Amount Of Substrate Harvested Following The Introduction Of An Antifungal Agent, November 2010, Benjamin Hedin
Tropical Ecology and Conservation [Monteverde Institute]
Optimal foraging theory dictates animals will behave in the most energetic favorable fashion, maximizing energy gained while minimizing energy lost. However, exceptions do exist, such as mating behaviors and predator avoidance. I show that oat flakes contaminated with antifungal powder, simulating secondary compounds, are selected less and at a lower rate by a colony of Atta cephalotes. This demonstrates the ability of the colony to recognize and discriminate against the contaminant to protect their symbiotic fungus. It also suggests that leafcutters, to an extent, can detect the amount or toxicity of the secondary compound. The willingness of the ants to …
Absence Of Polarity In Trail Pheromones And Use Of Sun-Compass Orientation In Leafcutter Ants Atta Cephalotes, November 2010, Marc A. Bliss
Absence Of Polarity In Trail Pheromones And Use Of Sun-Compass Orientation In Leafcutter Ants Atta Cephalotes, November 2010, Marc A. Bliss
Tropical Ecology and Conservation [Monteverde Institute]
The complex social system of leafcutter ants, Atta cephalotes (Formicidae) requires a high degree of organization and efficiency to ensure the survival of the colony. This suggests that communication between individuals is both common and intricate, especially during the complicated foraging process. Chemical signaling is employed by returning, laden ants along foraging trails. This study tested for the presence of polar properties within these trail pheromones to convey orientation cues to workers. Using manipulated foraging trails of a single colony in San Luis, Costa Rica, I observed individual ant behavior at different times of day. Rather than finding a correlation …
Anthocyanins And Delayed Greening: Inhibition Of Leafcutter Ants (Atta Cephalotes) In Inga Punctata (Mimosaceae) And Zygia Palmana (Fabaceae), May 2010, Antoinette Hertel
Anthocyanins And Delayed Greening: Inhibition Of Leafcutter Ants (Atta Cephalotes) In Inga Punctata (Mimosaceae) And Zygia Palmana (Fabaceae), May 2010, Antoinette Hertel
Tropical Ecology and Conservation [Monteverde Institute]
Leaves that undergo delayed greening with anthocyanins are suspected of having antiherbivore defenses in addition to low leaf nutrient content. This study examines two species with delayed greening, one with anthocyanins, Zygia palmana, and one without, Inga punctata, to determine whether anthocyanins deter herbivores more than low nutritional quality. Leaf samples were taken from 20 trees in Monteverde, Costa Rica. Chlorophyll a, chlorophyll b, carotinoids and anthocyanins were extracted from leaves and tested for concentrations as well as chemical preference to an herbivore, Atta cephalotes. There was a significant preference for older, fully green leaves in each species (p=.041), as …
Effect Of Ground Temperature And Nest Differences On Productivity And Worker Size In Atta Cephalotes (Hymenoptera Formicidae), May 2010, Hannah Fried-Petersen
Effect Of Ground Temperature And Nest Differences On Productivity And Worker Size In Atta Cephalotes (Hymenoptera Formicidae), May 2010, Hannah Fried-Petersen
Tropical Ecology and Conservation [Monteverde Institute]
Atta cephalotes is one of the few species that does better in grassy pastures and secondary growth and their abundance, persistent foraging, and that they collect from a lot of different tree species has earned them the reputation of huge agricultural pests. A. cephalotes are poikilotherms meaning their internal body temperature fluctuates greatly with temperature. For this reason, it has been purported that these leaf-cutter ants will only collect leaf fragments at certain temperatures and that different sized workers have different temperature tolerances. The objective of this study was to look for relationships between temperature, productivity, and worker size in …
Polyethism In Eciton Burchellii Army Ants: A Look At Task Specializations Of Worker Castes, May 2010, Colleen Nell
Polyethism In Eciton Burchellii Army Ants: A Look At Task Specializations Of Worker Castes, May 2010, Colleen Nell
Tropical Ecology and Conservation [Monteverde Institute]
Insect societies, specifically Eciton burchellii army ants have had high ecological success due to polyethism within the colony. This division of labor within the colony increases efficiency and therefore fitness of the colony, which has selected four morphologically and behaviorally defined castes; majors, submajors, media, and minims. Samples of these castes show strong division of labor and roles throughout the colony. Majors are shown to restrict themselves to the column and bivouac where defense is of highest necessity. Submajors have morphologically evolved to carry large prey and maintain column flow. Media are found to be generalists, reinforcing essential functions of …
Ant-Plant Coevolution: A Systematic Evaluation Of The Myrmelachista Haberi (Formicinae) And Ocotea Sp. (Lauraceae) Symbiosis, May 2009, Murtaza Paghdiwala
Ant-Plant Coevolution: A Systematic Evaluation Of The Myrmelachista Haberi (Formicinae) And Ocotea Sp. (Lauraceae) Symbiosis, May 2009, Murtaza Paghdiwala
Tropical Ecology and Conservation [Monteverde Institute]
I have evaluated the relationship between Myrmelachista haberi and Ocotea sp. (Los Llanos) to provide definitive evidence supporting the nature of the symbiosis and possible explanations in terms of co-evolutionary history. This interaction has been described in terms of benefit to the ant-domatia and nutrition via phloem-feeder farming – but benefits from the plants perspective have gone largely unstudied. McNett (2009) attempted to quantify the nature of the relationship by monitoring the uptake and movement of stable isotopes through each of the three participating species. This study found that nutrients do not transfer between the organisms, but left the possibilities …
Eciton Burchellii: Polymorphism Of Submajor Caste And Foraging Efficiency, May 2009, Samantha Alger
Eciton Burchellii: Polymorphism Of Submajor Caste And Foraging Efficiency, May 2009, Samantha Alger
Tropical Ecology and Conservation [Monteverde Institute]
Due to the link between efficiency and fitness, there should be selective pressure for morphology and behavior that promotes foraging efficiency. Among social insects, selective pressures act on individuals, shaping the physical castes of a colony. The highly polymorphic army ant, Eciton burchellii, has castes with morphological adaptations to allow task specialization. This study investigates what selective pressures are acting to shape the polymorphism of the submajor caste in E. burchellii. Ants were collected to find a relationship between ant caste and the prey’s biomass, width, and length. Results show that prey width is the greatest pressure effecting transportation efficiency, …
Diversity And Morphological Variation In Formicidae In Three Strata Of The Monteverde Cloud Forest, August 2008, Peter A. Larson
Diversity And Morphological Variation In Formicidae In Three Strata Of The Monteverde Cloud Forest, August 2008, Peter A. Larson
Tropical Ecology and Conservation [Monteverde Institute]
This study examines the arboreal presence of ants. Comparisons of diversity at three forest strata, canopy, mid-level, and forest floor were analyzed. Measurements were also made of leg length to body length and compared across the strata. The hypothesis is that arboreal ants will have a higher leg to body ratio. Finally a representation of each ant species, except three under-represented species was dropped from the canopy to test for the ability to “glide”. Conclusive results showed that ant diversity is greatest at the mid-stratum (H’ = 1.82). The remaining two strata, canopy and floor, showed similar diversity values (H’ …
Atta Cephalotes (Formicidae) As A Reliable Bioassay For Anti-Fungal Compounds In Plants Of Monteverde, Costa Rica, December 2007, Annie Chisholm
Atta Cephalotes (Formicidae) As A Reliable Bioassay For Anti-Fungal Compounds In Plants Of Monteverde, Costa Rica, December 2007, Annie Chisholm
Tropical Ecology and Conservation [Monteverde Institute]
Studies have shown Atta cephalotes (Formicidae) to be selective in choosing host plants, avoiding those that contain nonpolar secondary compounds harmful to their mutualistic fungus (Howard 1988). Due to this selectivity, several studies have found A. cephalotes to be a reliable bioassay tool for detecting antifungal properties of plants (Ozaki 1993; Taylor 1995). This experiment tests the acceptability of A. cephalotes towards six Costa Rican plants with known anti-fungal compounds. It was hypothesized that A. cephalotes would selectively avoid extracts of these plants. The frequency of removal of oat flakes dipped in the anti-fungal and control treatments was measured. A. …
Worker Size, Load Mass, Speed, And Foraging Efficiency In Atta Cephalotes, November 2004, Zaynab Rezania
Worker Size, Load Mass, Speed, And Foraging Efficiency In Atta Cephalotes, November 2004, Zaynab Rezania
Tropical Ecology and Conservation [Monteverde Institute]
Optimal foraging models have been utilized extensively in the analysis of foraging behavior. Applied to the leaf-cutter ants, Atta cephalotes, these models may identify variables that affect individual and colony foraging efficiency. One colony of A. cephalotes in Cañitas, Costa Rica, was studied to determine the relationships between ant size, load mass, foraging speed, and efficiency. Head width, foraging speed, and load mass were measured for 150 individuals, and efficiency and load/ant size ratio were calculated. The relationships between these variables were analyzed using linear and logarithmic regressions. Ant head width and load mass showed a positive relationship (p < 0.0001), as did head width and foraging speed (p < 0.0001). There was no significant relationship between load mass and speed when individuals of all head sizes were included in a linear regression, however, when separated into small, medium, and large head size groups, linear regressions showed a significant relationship for the small (p < 0.0001) and medium size groups ( p = 0.0007). There were positive correlations between ant head size and efficiency (p < 0.0001), as well as between load mass and efficiency (p < 0.0001). Ant head size and the load/ant size ratio also showed a positive relationship (p < 0.0001). These results indicate that larger ants achieve greater foraging efficiency than smaller ants. In addition, it may be more efficient to transport heavier loads, despite their negative effect on foraging speed. There are many compromises involved in optimal foraging models, as increasing one aspect of efficiency may reduce another.
Trail Fidelity In Atta Cephalotes, November 2004, Amy Romer
Trail Fidelity In Atta Cephalotes, November 2004, Amy Romer
Tropical Ecology and Conservation [Monteverde Institute]
Trail fidelity in Atta cephalotes was tested through marking experiments by comparing the movement of 500 marked workers that were removed but replaced on the same trail with the movement of a separate group of 500 marked workers that were displaced to a new trail. Trail fidelity was very high for replaced workers: 94% of workers observed at a census 24 hours after marking remained on the original trail. Trail fidelity was such a strong force in displaced ant behavior that by 24 hours after marking 74% had returned to their original trail. This indicates that worker ants are orientated …
Ant (Formicidae) Diversity, Species Richness, And Abundance In Response To Different Food Sources, August 2004, Sarah A. Wyatt
Ant (Formicidae) Diversity, Species Richness, And Abundance In Response To Different Food Sources, August 2004, Sarah A. Wyatt
Tropical Ecology and Conservation [Monteverde Institute]
More than 500 species of ants (family Formicidae: order Hymenoptera) have been found in Costa Rica (Gauld & Hanson 2000), and 46 of the 80 genera found in Costa Rica are known to live in the Monteverde area (Longino 2000). Some species of ants are known to exhibit food preferences for or against sugar and/or specific prey taxa (Dejean et al. 1999). The purpose of this study was to determine if species richness and diversity change in response to varying bait in traps. One hundred and twenty traps containing one of 6 kinds of bait (crustaceans, tuna, honey, peanut butter, …
Is Traffic Organized On Trails Of The Leaf Cutting Ant Atta Cephalotes?, November 2001, Angela C. Rao
Is Traffic Organized On Trails Of The Leaf Cutting Ant Atta Cephalotes?, November 2001, Angela C. Rao
Tropical Ecology and Conservation [Monteverde Institute]
The leaf cutting tribe Attini (Formicidae: Myrmicinae) shows numerous adaptations that increase foraging efficiency. Such adaptations are seen in their highly polymorphic caste systems, trails branching from many different exit holes, clearing and maintenance of foraging trails, and pheromonal signaling and recruitment. It is reasonable to assume that mechanisms exist that would reduce incidence of collisions, traffic jams, etc., on foraging trails. This hypothesis was tested by recording trail density and time, linear distance, and direction of ant travel on the trails of Atta Cephalotes and looking for certain trends. Ants traveling towards the nest were not found to vary …
Trail Clearing And Foraging Behaviors In Two Species Of Leaf Cutter Ants (Atta Cephalotes And Acromyrmex Coronatus), May 2001, Katy Zaksek
Tropical Ecology and Conservation [Monteverde Institute]
Leaf cutting ants play an integral role in tropical forest communities. Foraging strategies impact the harvest efficiency of a colony and in turn rates of herbivory on a forest community. Trail construction and foraging efficiency were compared between two species of leaf cutting ants (Atta cephalotes and Acromyrmex coronatus). Atta cephalotes constructed major trail systems and Acromyrmex coronatus, a species with smaller colony size, traveled between harvest sites on simple foraging lines across leaf litter. Significant differences existed across species with respect to traveling speed and burden ratios (ANOVA, p < 0.0001 and 0.0071, respectively) indicating benefits in maintaining unobstructed trails. Atta cephalotes trail clearing behaviors were investigated further by simulating natural obstructions. Colonies exhibited rapid removal of all objects placed on trails and removal time was significantly correlated with worker activity and distance from nest entrance (ANOVA, p = 0.0016 and 0.0163). This study attempts to demonstrate that A. cephalotes gains a competitive advantage over other leaf-cutting species, and reaps benefits, from trail construction and maintenance despite large initial investment.
Foraging Preference Of Atta Cephalotes (Hymenoptera: Formicidae), November 2000, Laurel Klein, Joseph Reid
Foraging Preference Of Atta Cephalotes (Hymenoptera: Formicidae), November 2000, Laurel Klein, Joseph Reid
Tropical Ecology and Conservation [Monteverde Institute]
Leaf cutter ants, Atta cephalotes, were found to make distinct tree species choices as herbivores in the premontane wet forest of Cerro Plano, Costa Rica. One trail from each of six nests was studied. Trail lengths varied, ranging from 3.30 m to 40.40m. Trees were identified along the trail, as well as the host tree at the end of the trails. Three leaves were taken from each tree and tested for toughness, thickness, and percent water content. The results for each test for each tree along a trail were compared to those for the host tree. The ants selected for …