Marked Ants Research Articles

Low Intraspecific Aggression Level, Cuticular Hydrocarbons, and Polydomy in the Bullet Ant.

Ants use chemical cues known as cuticular hydrocarbons (CHCs) for both intraspecific and interspecific recognition. These compounds serve ants in distinguishing between nestmates and non-nestmates, enabling them to coexist in polydomous colonies characterized by socially connected yet spatially separated nests. Hence, the aim of this study was to investigate the intraspecific aggression level between nestmates and non-nestmates of the bullet ant Paraponera clavata (Fabricius, 1775), analyze and compare their CHCs, and evaluate the occurrence of polydomy in this species. We conducted aggression tests between foragers, both in laboratory and field settings. To identify the chemical profiles, we utilized gas chromatography coupled with mass spectrometry (GC-MS). We marked the foragers found at nest entrances and subsequently recaptured these marked ants to validate workers exchange among nests. Across all nests, a low intraspecific aggression level was observed within the same area. However, a significant difference in aggression correlated to distance between nests. Analysis of the cuticular chemical profile of P. clavata unveiled colony-specific CHCs, both qualitatively and quantitatively. Notably, we observed instances of ants from certain nests entering or exiting different nests. This behavior, in conjunction with the observed low intraspecific aggression despite differences in CHCs suggests polydomy for this species. Polydomy can offer several benefits, including risk spreading, efficient exploitation of resources, potential for colony size increasing and reduced costs associated with foraging and competition.

Route learning during tandem running in the rock ant Temnothorax albipennis.

Many animals use information from conspecifics to change their behavior in adaptive ways. When a rock ant, Temnothorax albipennis, finds food, she returns to her colony and uses a method called tandem running to lead nestmates, one at a time, from the nest to the food. In this way, naive ants can learn the location of a food source. Less clear is whether they also learn navigational cues that guide them from nest to food, although this is often assumed. We tested this idea by tracing the routes of individually marked ants as they followed tandem runs to a feeder, returned to the nest, and later traveled independently back to the food. Our results show, for the first time, that tandem run followers learn specific routes from their leaders. Independent journeys back to the food source were significantly more similar to the routes on which the ants had been led, compared with the routes taken by other tandem runs. In contrast, the homeward journey did not resemble the tandem run route. These results are consistent with followers memorizing visual cues during the tandem run that are useful for recapitulating the outward journey, but not as effective when facing in the opposite direction on the homeward journey. We further showed that foraging routes improved through individual experience over multiple trips but not through the social transfer of route information via tandem running. We discuss our findings in relation to social learning and integration of individual and social information in ants.

Foraging Distance of the Argentine Ant in California Vineyards.

Argentine ants, Linepithema humile (Mayr) (Hymenoptera: Formicidae), form mutualisms with hemipteran pests in crop systems. In vineyards, they feed on honeydew produced by mealybugs and soft scales, which they tend and protect from natural enemies. Few options for controlling Argentine ants are available; one of the more effective approaches is to use liquid baits containing a low dose of an insecticide. Knowledge of ant foraging patterns is required to estimate how many bait stations to deploy per unit area. To measure how far ants move liquid bait in vineyards, we placed bait stations containing sugar water and a protein marker in plots for 6 d, and then collected ants along transects extending away from bait stations. The ants moved an average of 16.08 m and 12.21 m from bait stations in the first and second years of the study, respectively. Marked ants were found up to 63 m from bait stations; however, proportions of marked ants decreased exponentially as distance from the bait station increased. Results indicate that Argentine ants generally forage at distances <36 m in California vineyards, thus suggesting that insecticide bait stations must be deployed at intervals of 36 m or less to control ants. We found no effect of insecticide on distances that ants moved the liquid bait, but this may have been because bait station densities were too low to affect the high numbers of Argentine ants that were present at the study sites.

Laterality of leaf cutting in the attine ant Acromyrmex echinatior

We tested the idea that leaf-cutting ants preferentially use one of their mandibles in the leading position when cutting leaves. We recorded the mandible position of both paint-marked and unmarked foragers from a laboratory colony of Acromyrmex echinatior during foraging bouts in two experiments 1 year apart (2012 and 2013). Both types of ants were ambidextrous in 2012, and so were unmarked ants in 2013. In contrast, marked ants in 2013 had a preference for leading with their right mandible. The individual laterality of these latter ants ranged from ambidexterity to about 70 % use of the preferred leading mandible. In 2013, we also estimated the cutting rate (length cut per second spent cutting) and harvesting rate (leaf area harvested per second spent cutting) of cutting events for marked foragers. Despite significant positive correlations between head size and both cutting and harvesting rates, the intensity of lateralization was better explained by cutting and harvesting rates than by head size. Specifically, the most lateralized foragers were the slowest and harvested the smallest leaf area per second. We interpret this association as evidence that lateralization was stronger for ants for which cutting was more challenging.

Seasonal Trends in Honeydew-Foraging Strategies in the Red Wood Ant, Formica yessensis (Hymenoptera: Formicidae)

The red wood ants Formica yessensis are known to support super colonies comprising thousands of nests, contain approximately 360 million workers, and over one million queens along the Ishikari coast, Hokkaido, northern Japan. Previous studies revealed the abundance of prey insects in Ishikari is very limited; suggesting that honeydew collected from aphids is a critical resource for F. yessensis. Furthermore, several reports suggested F. yessensis performs a generation change between late July and early August at the study site. The present study examined seasonal changes in F. yessensis honeydewforaging workers and specifically addressed the following: information transfer to aphid trees; fidelity to aphid trees; and changes in F. yessensis body size. Observation of marked ants revealed that information transfer to aphid trees occurred by direct guidance from older to younger foragers. Seasonal sampling indicated that honeydew-foraging ant body size decreased with progressive seasons. Large gaster coefficient of variation (CV) values showed two honeydew-foraging ant worker types were present in the super colony. The results revealed older foragers exhibited a large body size, which decreased in number towards autumn. Younger workers exhibited a smaller body size, and initiated honeydew foraging after emergence. Honeydew is a critical resource, therefore information transfer to aphid tree location, and honeydew-foraging were the first priority tasks observed in F. yessensis at the study site.

Consensus decision making in the ant Myrmecina nipponica: house-hunters combine pheromone trails with quorum responses

Consensus decisions enable group-living organisms to coordinate collective tasks without the need for complex cognitive abilities or centralized leadership. Systems of nonlinear positive feedback, such as quorum responses, are thought to be integral to consensus decision processes that seek to optimize decision speed and accuracy while maintaining group cohesion, requirements typical of the house-hunting process in social insects. Studies of nest site selection in honeybees, Apis mellifera, and Temnothorax ants have revealed strong similarities in the manner in which consensus decisions are achieved, and imply a central role for quorum responses, but treatments of other species are scarce. I investigated the process of consensus decision making during colony relocation in the small colony ant Myrmecina nipponica. Colonies of individually marked ants were forced to relocate in experimental laboratory arenas, and given a choice of one or two alternative new sites. This species differs from other well-studied systems in using pheromone trails to navigate between old and new sites, and does not use obvious means of recruitment such as tandem running or adult transport. A quorum threshold apparently governed the switch to brood transport, which marked the final phase of the relocation. Furthermore, there was a strong relationship between inferred quorum threshold and colony size. A demonstration of the use of a quorum rule in M. nipponica would underline the central role of quorum responses in consensus decision making, despite interspecific variation in colony size and differing modes of recruitment and navigation.

Behavioral responses of acacia ants correlate with age and location on the host plant

In social insects, worker specialization in location-related tasks could occur if they return to the same location over time. Location and task fidelity was tested in the acacia ants Pseudomyrmex spinicola, which nest inside the swollen spines of the tree, and all workers enter the spines at night and during rain. Workers were marked and followed at three locations: on the leaves, tree trunk, and ground near the plant. Behavioral tests were performed, testing the reactions of marked ants toward the food used to feed the larvae (Beltian Bodies, “BB”), and to brood outside the spines. Marked ants and ants of known age were tested for responses to disturbance of the spines. Ants were more likely to occur in the location where they were originally marked. Trunk-marked ants discarded the BB when it had a foliole fragment attached to it, while leaf-marked ants carried it to the spine. Trunk-marked ants left larvae and exited from disturbed spines more frequently than other ants. Leaf-marked ants carried larvae and pupae more often than trunk-marked ants. Spine-marked ants left pupae more often than trunk- or leaf-marked ants. When considering age, older ants reacted aggressively when threatened, whereas younger ants protected the brood. However, younger ants reacted more aggressively when older ants were absent, and older ants were more aggressive in the presence of larvae. In sum, the spatial segregation of the ants coincided with behavioral differences, and different behavioral responses are related to the age of the ant.

Complexity at large

Complexity at large

Time-Ordered Networks Reveal Limitations to Information Flow in Ant Colonies

BackgroundAn important function of many complex networks is to inhibit or promote the transmission of disease, resources, or information between individuals. However, little is known about how the temporal dynamics of individual-level interactions affect these networks and constrain their function. Ant colonies are a model comparative system for understanding general principles linking individual-level interactions to network-level functions because interactions among individuals enable integration of multiple sources of information to collectively make decisions, and allocate tasks and resources.Methodology/FindingsHere we show how the temporal and spatial dynamics of such individual interactions provide upper bounds to rates of colony-level information flow in the ant Temnothorax rugatulus. We develop a general framework for analyzing dynamic networks and a mathematical model that predicts how information flow scales with individual mobility and group size.Conclusions/SignificanceUsing thousands of time-stamped interactions between uniquely marked ants in four colonies of a range of sizes, we demonstrate that observed maximum rates of information flow are always slower than predicted, and are constrained by regulation of individual mobility and contact rate. By accounting for the ordering and timing of interactions, we can resolve important difficulties with network sampling frequency and duration, enabling a broader understanding of interaction network functioning across systems and scales.

An agent-based model of collective nest choice by the ant Temnothorax albipennis

Colonies of the ant Temnothorax (formerly Leptothorax ) albipennis can collectively choose the best of several nest sites, even when many of the active ants who organize the move visit only one site. Previous studies have suggested that this ability stems from the ants' strategy of graded commitment to a potential home. On finding a site, an ant proceeds from independent assessment, to recruiting fellow active ants via slow tandem runs, to bringing the passive bulk of the colony via rapid transports. Assessment duration varies inversely with site quality, and the switch from tandem runs to transports requires that a quorum of ants first be summoned to the site. These rules may generate a collective decision, by creating and amplifying differential population growth rates among sites. We test the importance of these and other known behavioural rules by incorporating them into an agent-based model. All parameters governing individual behaviour were estimated from videotaped emigrations of individually marked ants given a single nest option of either good or mediocre quality. The time course of simulated emigrations and the distribution of behaviour across ants largely matched these observations, except for the speed with which the final transport phase was completed, and the overall emigration speed of one particularly large colony. The model also predicted the prevalence of splitting between sites when colonies had to choose between two sites of different quality, although it correctly predicted the degree of splitting in only four of six cases. It did not fully capture variance in colony performance, but it did predict the emergence of variation in individual behaviour, despite the use of identical parameter values for all ants. The model shows how, with adequate empirical data, the algorithmic form of a collective decision-making mechanism can be captured.

Resource Partitioning Among Colonies of Polygyne Red Imported Fire Ants (Hymenoptera: Formicidae)

Abstract Measurements of ant colony sizes and neighboring colony spatial structure figure importantly in a variety of socio-biological considerations. In this study, we used mass-marking and recapture techniques to quantify the foraging distribution and abundance of red imported fire ants, Solenopsis invicta Buren, on individual bait cards from neighboring polygyne (multiple queens) colonies. Ants in six to eight adjacent colonies, at each of 10 sites, were mass-marked a unique color. Ants were collected at olive-oil baits in a 10 by 10-m area consisting of 61 baits at each site. Stepwise nonlinear regression showed that the distance to baits, colony size, and average internidal (between nests) spacing were significant predictors of the foraging distribution of ants from colonies. Most marked ants were collected within ≈4 m of their colony. Foraging was more constrained at closer internidal distances. As internidal distances increased, colony foraging distances increased. There was a significant differenc...

Determining the foraging range and origin of resurgence after treatment of Argentine ant (Hymenoptera: Formicidae) in urban areas.

The foraging range and distribution of Argentine ant, Linepithema humile (Mayr), colonies in urban areas of southern California extended at least 61 m (200 feet) from feeding stations and structures. Ants were fed at 25% sucrose feeding stations containing 0.01% fluorescent brighter (FB28). Within 14 d, from 77-90% of the ants sampled next to the feeding stations were positive for FB28. The percentage of ants with FB28 declined gradually to approximately 55% 61 m away from the feeding station. The percentage of marked ants in the controls didn't change over the 4-wk-test period. There were approximately 290,000 ants visiting the monitored stations each night before treatments. The 0.0001% fipronil baits and 0.06% fipronil SC sprays provided significant reductions in at least 4 wk. The percentage of ants marked with FB28 decreased significantly in both bait and spray treatments over 4 wk suggesting that the resurgence of ants in treated areas were because of immigration from untreated areas. It is likely that much larger areas will need to be treated to control Argentine ants in urban settings, especially if baits are being used.

An Improved and Quantified Technique for Marking Individual Fire Ants (Hymenoptera: Formicidae)

Individual fire ants, Solenopsis invicta Buren, were marked with dots of Markal brand Ball Point Paint Markers. Marked ants were returned to the colony while the paint was still wet. The marks were slowly lost over a 100-day period, with one mark lasting 119 days. No mortality could be attributed to the paint. The proportion of ants retaining marks over time can be expressed as a simple exponential decay model: proportion with marks = 0.7665 * exp (-0.0175 * time in days). The technique will be useful in assessing basic behavioral characteristics, such as polygyne versus monogyne interactions, nestmate discrimination, foraging profiles, and in assessing impact of candidate biological control organisms on behavior and survivorship of fire ants.

Pinpointing food sources: olfactory and anemotactic orientation in desert ants, Cataglyphis fortis.

Desert ants, Cataglyphis fortis, search for a repeatedly visited food source by employing a combined olfactory and anemotactic orientation strategy (in addition to their visually based path-integration scheme). This behaviour was investigated by video-tracking consecutive foraging trips of individually marked ants under a variety of experimental conditions, including manipulations of the olfactory and wind-detecting systems of the ants. If the wind blows from a constant direction, ants familiar with the feeding site follow outbound paths that lead them into an area 0.5-2.5 m downwind of the feeding station. Here, the ants apparently pick up odour plumes emanating from the food source and follow these by steering an upwind course until they reach the feeder. If the food is removed, foragers usually concentrate their search movements within the area downwind of the feeding site. Only when the wind happens to subside or when tail-wind conditions prevail do the ants steer direct courses towards the food. Elimination of olfactory input by clipping the antennal flagella, or of wind perception by immobilising the bases of the antennae, altered the foraging behaviour of the ants in ways that supported these interpretations. Ants with clipped flagella were never observed to collect food items.

Spatio-Temporal Learning by the ant Ectatomma Ruidum

ABSTRACT We tested, under field and laboratory conditions, whether the neotropical ant Ectatomma ruidum Roger can learn several associations between temporal and spatial changes in the daily pattern of food availability. Honey was shuffled between two or three feeding sites following a fixed daily schedule. Foragers learnt to associate particular sites with the specific times at which food was available, individually marked ants being observed on the correct sites at the correct times. Some ants anticipated the time of food delivery by approximately 30 min, and it was not necessary for them to be rewarded at the first stage of the sequence of food collection to continue their search for honey according to the correct schedule of reward. Ants also followed the same schedule when no honey was supplied at each stage of the sequence, and they stayed at the expected unrewarded site for a period equivalent to the reward period of the corresponding training phase, indicating that they had learnt when and for how long the food was available. Thus, ants rely on their spatio-temporal memory rather than on local cues coming from the honey source to guide them.

Foraging in the giant forest ant,Camponotus gigas(Smith) (Hymenoptera: Formicidae): evidence for temporal and spatial specialization in foraging activity

The foraging behaviour of the giant ant Camponotus gigas, was studied in primary lowland rainforest in Brunei. Nests, found mainly in soil at the base of trees or in fallen timber, were present at a density of 14 per hectare. Foragers were active nearly 24 h per day but much higher levels of activity were recorded at night. By day major and minor workers foraged singly or in small groups on the ground, and by night they ascended in a steady stream into the canopy. It is suggested that the canopy is avoided during the day due to high temperatures and low humidity, and the ground is avoided at night due to increased predatation risks. Overall, < 10% of foragers returned laden suggesting that most feeding took place while foraging. The most common food item retrieved was fungus although arthropods and arthropod remains, vertebrate remains and small fruits and seeds were also gathered. Relatively more arthropods were retrieved at night. By watching individually marked ants, it was found that different individ...

Site fidelity in foraging wood-ants Formica aquilonia yarrow and its influence on the distribution of foragers in a regenerating environment

The proportions of the population of red wood-ants Formica aquilonia Yarrow, foraging for sucrose at two artificial feeding sites in the laboratory, approximated to those predicted by the ideal free distribution (Lamb and Ollason, 1993). It was assumed that, for the foraging population to attain the ideal free distribution, each individual would visit and assess the availability of food at both feeding sites and distribute its foraging effort in proportion to the rate of regeneration of food. In order to demonstrate this, large samples of foragers at each of the feeding sites were colour-marked according to site. It was expected that the marked sample of foragers would in time become distributed as predicted by the ideal free distribution; instead, the distribution of marked ants was biased toward the site where they had been marked. Hence some individuals are not continually visiting and feeding at both patches, and such individuals will not be able directly to assess their feeding rates at each patch. There is, in principle, no way that such individuals can distribute themselves as predicted by the ideal free distribution, and as the site-faithful ants form a large proportion of the population, it appears that there is no way that the members of such a population can become so distributed. One resolution of this apparent paradox is provided by the behaviour of the mobile ants, the existence of which is demonstrated by observations of marked ants foraging at the site other than that at which they were marked. If the mobile members of the population assess the quality of both patches and distribute themselves to maximise their rates of feeding, the whole population will become distributed as predicted by the ideal free distribution. A modification of Ollason's (1987) model shows how this distribution could develop. It emerges that there is a minimum proportion of mobile ants in a population, below which the ideal free distribution will not develop, and that the distribution of foragers will depart from the ideal free distribution increasingly as the discrepancy between the regeneration rates of the patches of food increases.

Individual food source fidelity in the neotropical ponerine antEctatomma ruidumRoger (Hymenoptera Formicidae)

Foragers of the ponerine ant Ectatomma ruidum Roger can be classified into two behavioural subcastes: prey-hunting and nectar-collecting ants. Observations on foraging activities of nectar-collecting workers specialized on the extrafloral nectaries of the orchid, Spathoglotis plicata, were made in a neotropical forest located in Guadeloupe, using marked ants. Although foraging activity was mainly diurnal, the activity rhythm of these specialized workers showed a shift at the end of the afternoon, before sunset. Most foragers come back to the nest at this time but, by contrast, those collecting nectar on orchids increase their activity. This increase is linked with the secretion cycle of extrafloral nectaries which exhibit a strong activity at this time. Behavioural and ecological implications of the spatial and temporal learning involved in this food site fidelity are discussed.

Flexible seed selection by individual harvester ants, Pogonomyrmex occidentalis

Individual seed harvester ants (Pogonomyrmex) have been shown to specialize on specific seed types. We examined possible mechanisms for seed specialization and tested whether fidelity to food type limits the foraging decisions of individual western harvester ants, Pogonomyrmex occidentalis. The seed selection regimes of individually marked ants foraging at piles of two seed types were described and related to differences in seed quality and colonial dietary history. Individual foraging choices were affected by multiple factors, including seed caloric rewards, the previous seed selected, and the dietary history of the colony. Individual seed choices generally converged on the most energetically profitable species, suggesting that foragers exhibit labile preference. However, for a portion of the foragers, seed specialization was also partially due to constancy, defined as a tendency to select seed species that were previously collected. When colonies were presented with one seed type for 1 h and then were offered a mix of that seed and a novel seed type, individuals showed a strong preference for the novel seeds. Such rapid changes in seed preference argue strongly that individual P. occidentalis ants are highly flexible in seed choice and that resource assessment by these ants is more complex than simple maximization of net energetic return.

Estimation of Worker Numbers in Ant Populations after Marking with Europium

Neutron activation analysis after internal marking with natural Europium (Eu) was tested for its effectiveness in mark - recapture estimations of colonies of Myrmica rubra L., M. scabrinodis Nyl. and Lasius niger L. Eu appeared to be a reliable marker, not inducing extra mortality. Contamination of unmarked ants was insignificant except for L. niger, in which long starvation periods were necessary after marking to prevent transfer. In all species, marked ants could be detected for five weeks, but retention of marks was much better in L. niger than in Myrmica. Estimates of eight Myrmica-colonies with the use of Eu proved to be trustworthy, when compared with worker numbers collected by excavating and counting the colonies. Population estimates of thirty-five colonies of M. rubra and M. scabrinodis occurring in three sites of a coastal plain are presented. The data are discussed in relation to particular qualities and stress factors in these habitats.