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The biotic resistance hypothesis asserts that native species may hinder the invasion of exotic species, which can occur either directly or indirectly by influencing interactions between exotic and local species. Aphid-tending ants may play a key role in the indirect biotic resistance to plant invasion. Ants may protect aphids, thus increasing their negative effect on exotic plants, but may also deter chewing herbivores, thus benefiting exotic plants. We studied native aphid-tending ants (Dorymyrmex tener, Camponotus distinguendus, and Dorymyrmex richteri) on exotic nodding thistles (Carduus thoermeri), which are attacked by thistle aphids (Brachycaudus cardui) and thistle-head weevils (Rhinocyllus conicus). We evaluated the impact of ants, aphids, and weevils on thistle seed set. We compared ant species aggressiveness towards aphid predators and weevils and performed ant-exclusion experiments to determine the effects of ants on aphid predators and weevils. We analysed whether ant species affected thistle seed set through their effects on aphids and/or weevils. The ant D. tener showed the most aggressive behaviour towards aphid predators and weevils. Further, D. tener successfully removed aphid predators from thistles but did not affect weevils. Excluding D. tener from thistles increased seed set. Analyses supported a negative indirect pathway between the aggressive D. tener and thistle seed set through aphid populations, while the other ant species showed no indirect effects on thistle reproduction. Therefore, aggressive aphid-tending ants may enhance biotic resistance by increasing aphid infestation on exotic invasive plants. This study highlights the importance of indirect biotic resistance in modulating the success of invasive species.

In social insects colony fitness is determined in part by individual worker phenotypes. Across ant species, colony size varies greatly and is thought to affect worker trait variation in both proximate and ultimate ways. Little is known about the relationship between colony size and worker trait evolution, but hypotheses addressing the role of social structure in brain evolution suggest workers of small-colony species may have larger brains or larger brain regions necessary for complex behaviors. In previous work on odorous ants (Formicidae: Dolichoderinae) we found no correlation between colony size and these brain properties, but found that relative antennal lobe size scaled negatively with colony size. Therefore, we now test whether sensory systems scale with colony size, with particular attention to olfactory components thought to be involved in nestmate recognition. Across three species of odorous ants, Forelius mccooki, Dorymyrmex insanus, and D. bicolor, which overlap in habitat and foraging ecology but vary in colony size, we compare olfactory sensory structures, comparing those thought to be involved in nestmate recognition. We use the visual system, a sensory modality not as important in social communication in ants, as a control comparison. We find that body size scaling largely explains differences in eye size, antennal length, antennal sensilla density, and total number of olfactory glomeruli across these species. However, sensilla basiconica and olfactory glomeruli in the T6 cluster of the antennal lobe, structures known to be involved in nestmate recognition, do not follow body size scaling observed for other structures. Instead, we find evidence from the closely related Dorymyrmex species that the larger colony species, D. bicolor, invests more in structures implicated in nestmate recognition. To test for functional consequences, we compare nestmate and non-nestmate interactions between these two species and find D. bicolor pairs of either type engage in more interactions than D. insaus pairs. Thus, we do not find evidence supporting a universal pattern of sensory system scaling associated with changes in colony size, but hypothesize that observed differences in the olfactory components in two closely related Dorymyrmex species are evidence of a link between colony size and sensory trait evolution.

Social insects utilise a complex spatial orientation system mediated by chemical signals. This study investigated how the foraging behaviour of ants (Dorymyrmex thoracicus) varies depending on the quantity of an available resource using a field experiment. Further, we demonstrated computationally that ant displacement is compatible with a model based on pheromone deposition. Our experiment tested how the resource size (large or small) and availability (one or two simultaneous patches) of resources offered influence the number of recruited ants (traffic flow) and the speed of traffic flow both moving towards a resource and returning to the colony. The results showed that the returning flow was higher than the going flow independent of resource. The traffic flow towards a single resource was higher than the flow for either of two simultaneous resources patches offered; thus, multiple resources sources split the flow, regardless of the fact that resource size did not affect foraging choices. Our results indicated that the ants used an orientation mechanism that can be reproduced by a theoretical computer model. With our model, we showed that initially, the displacement of ants followed no clearly detectable pattern. However, with increasing levels of ant recruitment and consequent pheromone deposition on the most used trails, returning displacement revealed the formation of shorter and more organised trails. The model revealed key transition between periods of order and disorder that continued until the flow of information reached an organised state (Shannon entropy). This study highlights an exceptional mechanism of foraging optimisation in eusocial insects.

Symbiosis between plants and ants include examples in which the plant provides shelter and/or food for ants that, in turn, act in the defense or in the dispersion of seeds from the host plant. Although traditionally referred as mutualistic, the results of these interactions may vary with the ecological context in which patterns are involved. A range of species have facultative association with Turnera subulata (Turneraceae). Here, using behavioral bioassays, we investigated the effects of the most frequent ant species associated with T. subulata (Brachymyrmex sp.1, Camponotus blandus (Smith), Dorymyrmex sp.1, Crematogaster obscurata Emery, and Solenopsis invicta Buren) in the dispersion of plant host seeds and in the number of seedlings around the associated ant nests. We also evaluated the effects of these ant species in the germination of T. subulata seeds, in the consumption of elaiosome, and in the attractiveness to elaiosome odor. Our results showed that the ant species associated with T. subulata presented variation in the attraction by the odor and in the rate of consumption of the elaiosomes. However, none of the ant species studied contributed significantly to the increase of seed germination and seedling growth. Our results suggest that the consumption of the elaiosome by ant species is not a determinant factor to the success of germination of T. subulata. However, such species could contribute indirectly to seed germination by carrying seeds to sites more fertile to germination. In general, our results help to elucidate the results of ecological interactions involving ants and plants.

The objective of this study was to survey the ants in an area of natural regeneration in the municipality of Alta Floresta, Mato Grosso, Brazil. Sampling of the myrmecofauna was performed by means of soil traps containing preservative liquid, distributed along a transect. After 48 hours in the field, the specimens were collected, quantified and separated on the basis of morphospecies classification, and sent for taxonomic identification. A total of 586 individuals were sampled in five genera and three subfamilies (Myrmicinae, Dolichoderinae and Formicinae), with the most abundant species being Dorymyrmex brunneum and Pheidole obscurithorax.

Aggregate extraction is an activity that has increased considerably in recent years in Patagonia, providing raw material for road paving and construction industry. This activity deeply impacts soil composition and the biota. Ants are among the most important inhabitants of soils, and are useful indicators of the impact of human activities on ecosystems. This study determines the effect of aggregate extraction activities on a community of ants in a semiarid area of Argentinean Patagonia. In two abandoned quarries, disturbed and nearby control areas were delimited; ants were sampled using pitfall traps and different environmental variables were measured. Our analysis show that many environmental variables were altered in disturbed sites, with a reduction in vegetation cover, modification of percentage of fine grain and soil humidity, and an increase in soil pH and temperature. Thirteen ant species were identified. The Opportunists predominated in disturbed sites, in particular the species Dorymyrmex tener. The results reveal for the first time the behaviour of the ant community of this semiarid region in the face of a disturbance that directly impacts the soil. The focus on stress-tolerant species for restoration purposes deserves further study. Fil: Pereda-Gomez, Marcelo E.. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina Fil: Pessacq, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigación Esquel de Montaña y Estepa Patagóica. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Esquel. Centro de Investigación Esquel de Montaña y Estepa Patagónica; Argentina Fil: Elizalde, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Introduced species can diverge from their source population when they become established in a new ecosystem. The Texas Horned Lizard (Phrynosoma cornutum) is native to the western United States (US) and was historically introduced to several locations in the southeastern US. We studied three introduced populations in South Carolina, US to determine if they exhibit dietary, morphological and genetic divergence from the native western US populations. We expected little divergence from western populations because P. cornutum is a specialist whose biology is largely shaped by its diet of Pogonomyrmex harvester ants. We show that the introduced populations have mixed ancestry between south Texas and more northern areas and experienced founder effects and genetic bottlenecks resulting in decreased genetic diversity. South Carolina lizards primarily consume ants (94%), but surprisingly, they did not eat harvester ants. Introduced lizards primarily eat Dorymyrmex ants, but each introduced population complements Dorymyrmex with significantly different amounts of other species of ants, insects and plant matter. Introduced populations have smaller body size and have different limb and head shapes compared to western populations. This study demonstrates successful persistence of an introduced vertebrate that may be attributed to phenotypic change, even in the face of reduced genetic diversity.

If on one hand, ant pollination is rare, on the other Asclepiadoideae flowers are the most complex among Eudicots. Both themes are exciting in pollination biology. Although there are records of ants with the ability to remove the pollinarium on this subfamily, the role of these insects as pollinators is not yet known. Therefore, we investigated the interaction between flowers and ants, as well as the associated features in two species of Asclepiadoideae, Ditassa capillaris and D. hastata. The studied species were both visited by Cephalotes inaequalis and Dorymyrmex thoracicus. We analyzed the common traits of ant pollination of the plant species, recorded the number of visit by ants, and carried out experiments of selective pollination, developing an effectivity index. Both Ditassa species have common traits of ant pollination, such as small bright flowers with exposed floral resource. The pollinarium is clip-shaped and resistant to the metapleural gland, which ensures effective pollination. Dorymyrmex thoracicus is a very frequent but not very efficient pollinator, whereas Cephalotes inaequalis is more efficient though at a lower frequency. Therefore, the total contributions of both ants to the pollination of both Ditassa species are similar. The features of both Ditassa species which favor ant pollination, include some synapomorphies within Asclepiadoideae. Furthermore, the efficiency of the ants as pollinators to the reproductive success of the plants was similar despite the different behaviors observed in both ant species. Hence, we suggest that the role of ants in pollination within this subfamily has been neglected.

Spider ants of the genus Leptomyrmex Mayr (Hymenoptera: Formicidae: Dolichoderinae) are conspicuous species of Australasian rainforests, with putative fossil relatives in the Neotropics and Europe. There is longstanding debate over the biogeographical history of the genus, with the Palaearctic and Neotropical regions proposed as alternate centres of origin. We propose a resolution of this debate with the recent discovery and analysis of an extant species from central Brazil, L. relictus sp.n., which we describe from workers, males and brood. We sequence ten nuclear genes in the new species and in several Australian Leptomyrmex species, and append these data to a 54-taxon, 10-gene data matrix previously generated for the subfamily Dolichoderinae. We conduct phylogenetic and divergence dating analyses, and re-evaluate the fossil record of the group. We recover Leptomyrmex relictus sp.n. as a member of the Leptomyrmex clade with high support. It is sister to the Australasian species, and the genus Leptomyrmex is, in turn, sister to a pair of Neotropical genera, Forelius and Dorymyrmex. We infer a Neotropical origin for the genus and estimate a mid-Eocene (46 Ma, 95% CI 56 to 36 Ma) origin for the crown genus and an Oligocene origin for the Australasian clade (29 Ma, 95% CI 40 to 19 Ma). We confirm placement of the Dominican amber species †L. neotropicus Baroni Urbani in the genus but reject a close relationship with the Palaearctic fossil taxa †Leptomyrmula Emery and †Usomyrma Dlussky, Radchenko & Dubovikoff, considering them incertae sedis in the subfamily (Dolichoderinae). In contrast to the mesophilic preferences of the Australasian species of Leptomyrmex, the new Brazilian species inhabits cerrado (dry savannah). Our results support a Neotropical origin for spider ants with dispersal to Australia. Rafting on west-bound currents and/or a historical diversity imbalance between Australia and South America are proposed as alternate hypotheses to explain a pattern of biased E–W mid-Tertiary dispersal for ants with austral distributions. This pattern is suggested by our results in conjunction with observations of other ant clades. Overall, our findings highlight the value of integrated taxonomy, critical interpretation of morphology, and a comparative phylogenetic framework when conducting palaeontological and biogeographical studies of insect species. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:6E9E6617-6E53-40B8-82C7-67F89A83C553.

Social insects have co-existed with microbial species for millions of years and have evolved a diversity of collective defenses, including the use of antimicrobials. While many studies have revealed strategies that ants use against microbial entomopathogens, and several have shown ant-produced compounds inhibit environmental bacterial growth, few studies have tested whether exposure to environmental bacteria represents a health threat to ants. We compare four ant species’ responses to exposure to Escherichia coli and Staphylococcus epidermidis bacteria in order to broaden our understanding of microbial health-threats to ants and their ability to defend against them. In a first experiment, we measure worker mortality of Solenopsis invicta, Brachymyrmex chinensis, Aphaenogaster rudis, and Dorymyrmex bureni in response to exposure to E. coli and S. epidermidis. We found that exposure to E. coli was lethal for S. invicta and D. bureni, while all other effects of exposure were not different from experimental controls. In a second experiment, we compared the antimicrobial ability of surface extracts from bacteria-exposed and non-exposed S. invicta and B. chinensis worker ants, to see if exposure to E. coli or S. epidermidis led to an increase in antimicrobial compounds. We found no difference in the inhibitory effects from either treatment group in either species. Our results demonstrate the susceptibility to bacteria is varied across ant species. This variation may correlate with an ant species’ use of surface antimicrobials, as we found significant mortality effects in species which also were producing antimicrobials. Further exploration of a wide range of both bacteria and ant species is likely to reveal unique and nuanced antimicrobial strategies and deepen our understanding of how ant societies respond to microbial health threats.

It was estimated the climate change adaptation of the main coffee production systems in Líbano, Tolima, Colombia, using diversity indicators. Three production systems were selected: agroforestry systems (AFS) with Cordia alliodora, AFS with plantain and in monoculture, with four replications, locating five sampling units to collect and identify the ant genera as diversity and adaptation indicators. The richness index of Margalef detected between systems (1.3 vs 0.6 vs 0.6 for AFS with C. alliodora, monoculure and AFS with plantain, respectively). The genera Cephalotes, Dorymyrmex, Hypoponera, Pachycondyla, Octostruma and Proceratium, which require abundant biomass and litter, were registered just in AFS with C. alliodora, coinciding with the depth of this layer. The AFS with C. alliodora present advantages due they improve conditions for the conservation of several groups of ants, which are indicators of diversity and climate change adaptation.

Biotic and abiotic factors affect the species richness and abundance of ants inhabiting arid and semiarid zones. We evaluated how soil surface temperature, texture, percentage of surface coarse fragments, and vegetation affected the composition, diversity, and distribution of ants inhabiting a mosaic of environmental conditions in a semiarid zone in central Mexico. We captured 22 ant species at five sites studied, with the top of Cutac hill (1,750 m altitude) and Terrace 2 (1,376 m altitude) the richest sites with 10 species each. Based on redundancy analyses, the percentage of clay followed by the percentage of coarse fragments at the surface of the soil were the variables most related to the composition of ants in these communities. Percentage of clay ranged from 16 to 26 and was positively related to abundance of Pheidole sp. 1 and negatively related to abundance of Dorymyrmex bureni Trager (R2 = 0.76, P = 0.04; R2 = 0.86, P = 0.02, respectively), whereas percentage of soil surface coarse fra...

Ants are social, and their metabolism should be measured on at least two levels: (i) the individual workers and brood of which the colony is composed and (ii) the colony in its entirety. Whole colony respiration, tempo (size-free running speed in body lengths per second) and whole colony activity were simultaneously measured for 15 species of ants in four subfamilies, and these data are related to average worker and whole-colony weight, activity, percentage brood and percentage fat. Across all 15 species, whole colony respiration rate (μL CO2 h−1) is linearly related to whole colony live weight (log–log slope = 1.0). Colonies composed of large workers respire less than colonies composed of an equal live weight of small workers, and colonies with high tempos respire more than lower tempo colonies of equal weight. The tempos and respiration rates of smaller ants tend to be higher, and a higher tempo exacts a cost in higher respiration independent of the effect of small body size. Individual worker respiration (μL CO2 h−1) scales to worker live weight with an exponent of 0.76. Whole colony specific respiration rate (μL CO2 g−1 h−1) is unrelated to colony live weight. The regressions of respiration rates against colony and worker dry weight, lean weight and metabolic weight have similar slopes to those of live weight but different intercepts. Respiration is not related to worker percentage fat, percentage brood or activity. Ant ecology, tempo, body size, polymorphism and colony size are discussed in relation to respiration.

We used the southern toad (Anaxyrus terrestris) as a model species to explore how an invasive species, the red-imported fire ant (Solenopsis invicta; hereafter RIFA), influences amphibian predator avoidance and movement behaviors. Our objective was to determine if toads spent less time near and moved more frequently in the presence of RIFAs compared to pyramid ants by comparing behavioral reactions of toads to RIFAs versus a control and pyramid ants versus a control. Laboratory experiments involved three treatments including no ants, RIFAs, and native pyramid ants (Dorymyrmex bureni) within an experimental arena. We randomly placed ants into one of two containers located at each end of the arena. For each trial we placed a toad into the experimental arena, allowed the toad to acclimate and then recorded its behavior. We calculated the proportion of time the toad spent near ants and the number of movements completed by each toad. Comparing the RIFA treatment to the pyramid ant treatment, toads spent 35 % less time on the half of the experimental arena near RIFAs (P = 0.0304). Toad movements were 1.5 times more frequent in trials with RIFAs than pyramid ants (P = 0.0488). We propose that southern toads associate RIFAs either with increased predation risk or risk of injury compared to pyramid ants. Although the behaviors we observed might lessen the direct effects of RIFAs on southern toads via predation and injury, the indirect effects of increased movement and avoidance of RIFAs could also influence toad fitness by decreasing reproductive and foraging success.

Made available in DSpace on 2018-11-26T17:26:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-03-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Although studies have shown enhancement of insects, birds, and plants in organically managed agroecosystems, information on arthropod diversity and abundance in conventional and organic sugarcane farms is scarce. This research was conducted to analyze and compare the diversity and abundance of edaphic arthropods in organic and conventional sugarcane by using pitfall traps. The study was conducted during 2 growing seasons in Jaboticabal, Sao Paulo, Brazil. In total, 13,244 individuals belonging to 190 morphospecies were collected. In the conventional system, 4,964 specimens were collected, representing 122 morphospecies distributed in 15 orders and 50 families. In the organic system, 8,280 individuals were captured, representing 142 morphospecies in 13 orders and 45 families. Ants of the genera Pheidole Westwood, Dorymyrmex Mayr, Camponotus Mayr, and Crematogaster Lund (Hymenoptera: Formicidae) were predominant. Higher abundance and richness of arthropods (especially predators and omnivores) were found in the organic than the conventional system, which could be important in regulating key pests of sugarcane. Our results show that the organic management in sugarcane increased the abundance and diversity of arthropods. Univ Estadual Paulista UNESP, Fac Ciencias Agr & Vet, Dept Fitossanidade, BR-14884900 Jaboticabal, SP, Brazil Univ Estadual Paulista UNESP, Fac Ciencias Agr & Vet, Dept Fitossanidade, BR-14884900 Jaboticabal, SP, Brazil

Animals frequently experience resource imbalances in nature. For ants, one resource that may be particularly valuable for both introduced and native species is high-carbohydrate honeydew from hemipteran mutualists. We conducted field and laboratory experiments: (1) to test if red imported fire ants (Solenopsis invicta) competed with native ants for access to mutualisms with aphids, and (2) to quantify the effects of aphid honeydew presence or absence on colony growth of native ants. We focused on native dolichoderine ants (Formicidae, Dolichoderinae) because they are abundant ants that have omnivorous diets that frequently include mutualist-provided carbohydrates. At two sites in the southeastern US, native dolichoderine ants were far less frequent, and fire ants more frequent, at carbohydrate baits than would be expected based on their frequency in pitfall traps. A field experiment confirmed that a native ant species, Dorymyrmex bureni, was only found tending aphids when populations of S. invicta were suppressed. In the laboratory, colonies of native dolichoderine ants with access to both honeydew and insect prey had twice as many workers and over twice as much brood compared to colonies fed only ad libitum insect prey. Our results provide the first experimental evidence that introduced ants compete for access to mutualist-provided carbohydrates with native ants and that these carbohydrates represent critical resources for both introduced and native ants. These results challenge traditional paradigms of arthropod and ant nutrition and contribute to growing evidence of the importance of nutrition in mediating ecological interactions.

Summary 1. As central place foragers, ants accumulate organic debris near their nests. Consequently, soil nutrient stocks are often enriched near the nest site. We investigated the hypothesis that plant-derived food sources, such as extrafloral nectar (EFN), can encourage soil-dwelling ant colonies to nest near the plant, thereby inadvertently providing the plant with an additional source of mineral nutrients. The study focused on a population of Acacia constricta, a North American shrub bearing EFNs. 2. Several lines of evidence supported the notion that food rewards drew ant nests close to A. constricta plants. Firstly, ant species that visit EFNs nested significantly closer to A. constricta plants than would be expected by chance, whereas this was not the case for two ant species that do not visit EFNs. Secondly, A. constricta plants with an ant nest occurring naturally underneath the canopy had greater foliar volume, more EFNs per leaf and more EFNs per cm of leaf rachis than plants lacking an ant nest under the canopy. Thirdly, experimental supplementation of the nectar resources on acacias led to the establishment of significantly more new nests near the plant, relative to controls. However, nectar supplementation did not affect acacia seed production within the year of the study. 3. Soil from the nests of three, EFN-visiting ant species contained higher average stocks of most mineral nutrients than nearby soils outside the influence of the nest. 4. To test whether A. constricta can assimilate the nutrients in ant nests, we fed 15N-labelled food to Dorymyrmex sp. (smithi complex) workers nesting near acacias. Twenty-four days later, the leaves of acacias with an experimentally fed ant colony under the canopy contained significantly higher 15N and %N than acacias without a nest under the canopy, indicating that acacias assimilated and benefited from nutrients derived from ants. 5.Synthesis. The results indicate that nectar resources can attract the nests of some ant species, and that plants may benefit from access to soil nutrients derived from ant nests. Our data support the hypothesis that EFNs may confer nutritive, as well as protective, benefits.

Military training, soil texture, and ground cover influence ant communities at Fort Benning, a military installation in west-central Georgia. We sampled 81,237 ground-dwelling ants (47 species in 20 genera) with pitfall traps at 40 sites on a continuum from nearly pristine forest to highly disturbed training areas. We also measured 15 environmental variables related to vegetation and soil. Sites disturbed by military training had fewer trees, less canopy cover, more bare ground, and more compact soils with shallower A-horizons than comparable undisturbed sites. Pheidole bicarinata, Dorymyrmex smithi, and Pogonomyrmex badius dominated the most highly disturbed sites. Competitively submissive myrmicines, such as Aphaenogaster and Crematogaster, and formicines, such as Camponotus and Formica, were abundant in the undisturbed sites. Solenopsis invicta occurred in all but the least disturbed sites. Ant community composition was a useful indicator of disturbance at Fort Benning.

A pilot study was conducted to investigate the impact of Solenopsis invicta management with an insect growth regulator bait (s-methoprene) on native ant species and to determine the responses of these species to S. invicta reduction. This invasive species alters the diversity and structure of different trophic levels of arthropod assemblages. Despite advances in S. invicta management using biological control agents, poison baits remain as the primary tool for effective fire ant management. However, the effect of these products on native ants is relatively unknown. Understanding these effects is critical to the development of S. invicta management strategies that include conservation of native ants. Native ants compete with S. invicta to some degree and can bolster efforts to release and establish exotic biological control agents to more effectively manage S. invicta. The study was carried out in Mumford, TX. Two treatments were used: a bait treatment that reduced S. invicta densities and a control. The treatments were randomly assigned to 1.33-ha blocks, replicated four times, and periodically inspected using complementary sampling techniques (pitfall traps, baited vials, manual collections, and nest surveys). Sixteen ant species were found among the two treatments. After S. invicta reduction, significant increases in densities of several other ant species were observed. Species within the assemblage shifted from the dominance by S. invicta to the dominance of the native pyramid ant, Dorymyrmex flavus McCook, which showed the most significant increase in bait treated blocks and was found to persist at densities significantly higher than the control for >2 yr after the last bait treatment. A temporary change in diversity was observed, indicating that use of a poison bait for S. invicta management benefited numerous resident species in the ant assemblage.

The effects of bait treatment(s) on population dynamics of Solenopsis invicta and Dorymyrmex flavus were studied, and various factors underlying the resurgence and persistence of D. flavus to reinvasion by S. invicta were studied in more detail. Pitfall traps, bait vials, transect sampling, and direct inspections were used to monitor densities of these two species, and inspections of D. flavus midden contents, video monitoring of D. flavus colonies, and studies of the fate of marked S. invicta were used to further clarify interactions of these two species, D. flavus abundance increased after the reduction of S. invicta with baits. D. flavus was also observed to sustain higher densities for an extended period (2 yr) after cessation of bait treatment and to exhibit antagonistic behaviors toward S. invicta, showing an ability to resist reinvasion of the treated area by S. invicta. Given these findings, D. flavus may retard domination of the ant assemblage by S. invicta. Additional studies are justified regarding how to enhance the role of this species in affected ecosystems.

We studied circular sand pile formation by two colonies of Brazilian Dorymyrmex ants, in which workers dumped sand excavated from their underground nest around the nest entrance hole. In most cases a worker dumped its load just beyond the ridge of the pile. Each dumped piece either stayed where it was deposited (81.9% in colony A and 73.0% in colony B) or rolled down the outer slope of the sand pile away from the entrance (17.9% in colony A and 27.0% in colony B). Ants almost never dumped in a way that resulted in the load rolling back to the entrance. When one side of the sand pile was experimentally removed, ants preferentially dumped soil on the now flat side, thereby restoring the original circular shape.

1. There is growing evidence that granivorous ants compete for seeds in desert ecosystems. But ants that diverge in diet may still interact strongly if existing colonies deter foundress queens. Granivores (seed eaters) and omnivores (ants that scavenge and feed on plant exudates) are common components of desert ecosystems. 2. The results of a 15-year granivore reduction experiment to explore the responses of two common omnivorous ants, Forelius cf pruinosus and Dorymyrmex insana, in a desert grassland were analysed. The food competition hypothesis predicts that granivore removal will have no net effect on omnivores. The spatial competition hypothesis predicts compensatory increases in omnivores on granivore removal plots. 3. A grain-based gut poison significantly reduced the densities of three of the four common granivorous ants. Densities of the large-colony (105-worker) omnivore Forelius did not increase with granivore removal. In contrast, and consistent with the hypothesis of competition for space, densities of the small-colony omnivore (102−103 worker) Dorymyrmex increased on granivore removal plots; however, this effect was only observed in years of high Dorymyrmex abundance.

Las hormigas son consideradas un elemento central en las zonas áridas debido principalmente a su papel como estructuradoras de las comunidades de plantas y por las diversas interacciones que establecen con otros organismos. Sin embargo, el conocimiento sobre la diversidad de las hormigas en las zonas áridas mexicanas es escaso. En este trabajo estudiamos la mirmecofauna de una localidad ubicada en el Valle semiárido de Tehuacán (San Rafael Coxcatlán). Nuestros objetivos fueron estimar la riqueza de especies de hormigas en este sitio y obtener un listado más extenso del Valle de Tehuacán, combinando nuestros datos con los de otro estudio. Finalmente comparamos la riqueza de especies de Tehuacán con la de otras dos zonas áridas mexicanas (Mapimí, Durango, en el Desierto Chihuahuense y Los Horcones, Sonora, en el Desierto Sonorense). Las hormigas de San Rafael Coxcatlán se colectaron entre noviembre de 1999 y enero de 2001 usando trampas “pitfall”. Se colectaron 28 especies pertenecientes a 14 géneros en cinco subfamilias, una riqueza relativamente alta para una zona tan pequeña (5 km²). Un análisis de conglomerados indicó que la mirmecofauna de Los Horcones y la del Valle de Tehuacán fueron las más similares. Ambos sitios además de compartir especies de amplia distribución, también comparten algunas de afinidad tropical tales como Pseudomyrmex major y Camponotus atriceps. Se han reportado patrones similares para la vegetación, aves y mamíferos de estos dos sitios los cuales han indicado que varios géneros de afinidad tropical se comparten. Este estudio representa uno de los primeros esfuerzos por conocer la diversidad de hormigas de una zona árida del centro de México.

Collectors use a variety of concentrations and types of alcohols to preserve ant specimens. We evaluated existing literature, experimental evidence, and expert myrmecological advice to determine what kind and concentration of alcohol will result in the best preserved specimens for card-point mounting and DNA extraction. For our experimental evaluation, we killed and stored Solenopsis invicta, Camponotus floridanus, and Dorymyrmex bureni workers in isopropanol and ethanol at four concentrations (70, 85, 95, 100%) over three time periods (24 h, 1 month, 6 months). We then compared specimen condition and amenability to manipulation for mounting on card points. Specimens stored in either 95% isopropanol or 95% ethanol for time periods longer than 24 h produced the best specimens for mounting. A literature review revealed that DNA is best preserved in 95–100% ethanol due to the ability of ethanol to more rapidly penetrate cellular membranes and deactivate DNase activity than other primary alcohols. We recommend that general collections of adult ant specimens should be killed and stored in 95% ethanol. Following this recommendation will result in ant specimens that are easier to mount for museum collections and better preserved for molecular studies. A variety of other killing and preservation techniques relevant to the study of ants are also discussed.

Theory predicts that consumers selecting among complementary resources will show stronger preferences for items that become relatively less available. I tested this hypothesis in a field study that compared the preferences of ant colonies given simultaneous access to experimental foods differing in carbohydrate and protein content. In the first part of the study, I examined the effect of nutrient supplementation on colony-level preference in the ant Dorymyrmex smithi. Colonies that had received a protein solution for 24 h consumed proportionally more carbohydrates than control colonies that had been given access to water, suggesting that colonies preferred nutrients when they became relatively rare. In the second part of the study, I compared colony-level preference among eight species of ants that differ in their relative access to carbohydrates and protein in the field. I found that species with relatively easy access to carbohydrates preferred protein, whereas species with greater access to protein preferred carbohydrates. These results suggest that the benefits of a nutritionally mixed diet coupled with differences in the relative availability of nutrients may explain variation in feeding decisions both within and among ant species. Key words: ants, complementary resources, foraging theory, preference. [Behav Ecol 15:63–70 (2004)]

Summary We examined the suitability of Solenopsis invicta Buren (Hymenoptera: Formicidae) as prey for a native antlion, Myrmeleon crudelis Walker (Neuroptera: Myrmeleontidae), in south Florida. We found that average growth rate was significantly lower and mortality was significantly higher for M. crudelis larvae fed S. invicta workers than for M. crudelis larvae fed Dorymyrmex bureni (Trager) (Hymenoptera: Formicidae) workers. Thus, S. invicta appears to be unsuitable prey for M. crudelis and may have a negative impact on M. crudelis and other ant predators in areas where it invades.

1. Although the majority of lycaenid–ant associations is facultative, few studies have documented the protection benefits provided by ants to lycaenids that are tended facultatively (Pierce & Easteal, 1986; Peterson, 1993). 2. Larvae of Hemiargus isola (Lepidoptera: Lycaenidae) feeding on Dalea albiflora are tended facultatively by several species of ant. In 1999 and 2000, the levels of parasitism and the identities of attendant ants were determined for larvae of H. isola. In addition, the presence of ants was manipulated experimentally to determine the efficacy of protection provided by attendant ants to H. isola. 3. Lycaenids were parasitised by a braconid wasp, Cotesia cyaniridis (Riley), and a tachinid fly, Aplomya theclarum (Scudder). In 1999 and 2000, 62 and 65% of larvae were parasitised; the percentage of the population parasitised did not differ significantly between years. In both 1999 and 2000, parasitism by the braconid wasp C. cyaniridis accounted for > 99% of all parasitism events. 4. Four species of ant, Crematogaster sp., Dorymyrmex sp., Forelius sp., and Formica sp., were associated with 88–99% of the tended lycaenids collected in both 1999 and 2000. For both years, there was a single, numerically dominant species associated with >80% of the tended larvae collected, but the identity of this numerically dominant ant differed between years. 5. Experimental exclusion of ants from D. albiflora plants resulted in 78% larval mortality as a result of parasitism, nearly twice that of larvae that were tended by ants on unmanipulated plants.

Although insects have been identified as valuable bioindicator species, insect diversity in coastal sand dunes is understudied. Our study presents the first survey focused on Georgia's barrier island ant assemblage. We surveyed the primary and secondary dunes of Cumberland, Little St. Simons, and Sapelo islands in the summers of 2016 and 2017 using protein baits to recruit scavenging ants that forage on dunes and beaches. We placed 4863 baits over the 2 sampling seasons; 2458 recruited ants. We documented 29 ant species, including 3 new records for the state: Dorymyrmex reginicula, Pheidole navigans, and Solenopsis globularia. Our survey provides a baseline for future projects to evaluate disturbance and ecosystem health on Georgia's barrier islands.

Stress-tolerance strategies in ants have been little studied in the context of ant communities. To examine this relationship, the behaviour and activity patterns of several dolichoderine ants, Forelius nigriventris Forel and Dorymyrmex exsanguis Forel and allies, with other members of a species-rich, scavenging ant assemblage in two habitats in the Argentine Chaco was studied. Both groups of dolichoderines were more active in the overgrazed-desertified habitat than in the forested habitat. Forelius nigriventris was relatively thermophilic, and D. exsanguis and allies were active over a broad range of environmental conditions and were tolerant of cold conditions. These dolichoderines were subordinate in aggressive interactions with other species at baits, and were abundant at baits only when other species were absent. Competitive interactions may have led to stress tolerance in these ants. Stress tolerance on a local scale may also permit the geographic distribution of these ants (particularly D. exsanguis ) into zones of relatively harsh climate.

1 Larvae of the North American lycaenid butterfly Hemiargus isola Reakirt tended by the ant Formica perpilosa Wheeler often enter nests of this ant species, and pupate in tunnels and chambers near the surface. Untended larvae and those tended by the ants Dorymyrmex Forel sp. (smithi complex), Forelius foetida (Buckley), and Myrmecocystus mimicus Wheeler pupate in crevices in the ground, under bark, and on leaves; but rarely inside ant nests. 2 The location and structure of F.perpilosa nests facilitates discovery by H.isola prepupae. At the southeast Arizona study site, F.perpilosa nests are located at the base of H.isola's host plant, whereas other species’nests are in open ground. Also, F.perpilosa nest openings are wide, whereas those of other species may be too narrow for prepupae to enter. 3 Prepupae associated with F.perpilosa spent 67% less time on the ground searching for pupation sites than prepupae associated with other ant species. Pupae in artificial chambers connected to F.perpilosa nests were 4–5 times less likely to disappear overnight, presumably due to predation, than those not connected to nests. 4 Formica perpilosa ants tend pupae inside nests. However, in the laboratory experiments tended pupae did not lose more weight prior to eclosion than untended ones, suggesting that chemicals or sounds produced by pupae as ant attractants are inexpensive, or are produced whether or not ants are present. 5 Newly-eclosed butterflies exited nests unmolested by ants in the field, but were attacked if confined with ants for several minutes after eclosion in the laboratory.

Two dry forests of southwestern Ecuador separated 43 km from each other, one situated at 460 m above sea level and the other at 680 m, are surveyed for ants giving a total of 28 species collected manually and from pitfall traps. Eleven species are shared between the sites whilst four are exclusive to one site and 13 to other. Differences in humidity, rainfall seasonality, and disturbance regimes may account for at least part of the differences observed between the ant communities of the two sites. Dorymyrmex pyramicus peruvianum Wheeler, 1919 and Pseudomyrmex kuenckeli (Emery, 1890) are reported from Ecuador for the first time. Cardiocondyla emeryi Forel, 1881 and Camponotus conspicuus zonatus Emery, 1894 are reported from mainland Ecuador for the first time. The genus Dorymyrmex Mayr, 1866 is recorded from Ecuador for the first time.

Ants are highly abundant in neotropical regions, with certain species adapted to the urban environment, where they can cause damage to human health. The main method for controlling ants consists of using organosynthetic insecticides, which are potentially toxic to the environment. Essential plant oils are considered a viable alternative to the use of conventional insecticides. In this study, we analyze the bioinsecticidal activity and repellence of patchouli essential oil (Pogostemon cablin) against three species of urban ants: Camponotus melanoticus, Camponotus novograndensis, and Dorymyrmex thoracicus. The chemical composition of the essential oil was analyzed by GC-MS and GC-FID. The major compounds were patchoulol (36.6%) followed by α-bulnesene (13.95%), and α-guaiene (11.96%). Toxicity and repellency bioassays were performed using the essential oil over the ants, and mortality evaluations were performed at 4, 24, and 48 h after performing the bioassays. Mortality percentage of the ants on 7 μg/mg was on average 84%. The essential oil of P. cablin displayed toxicity against all three species of urban ants, with the lowest LD₅₀ being observed for D. thoracicus (2.02 μg oil/mg insect) after 48 h of exposure compared to C. melanoticus (2.34 μg oil/mg insect) and C. novogranadensis (2.95 μg oil/mg insect). The essential oil of P. cablin was strongly repellent to the three species of ants in all concentrations tested (0.01% and 1% v/v). Considering the potential toxicity and repellency of the P. cablin essential oil to the urban ants, future studies could investigate the practical application of this oil to control of this insects.

The aim of the present study was to evaluate the use of mini-Winkler extractor and pitfall traps as appropriate and complementary methods to sample ant communities in the phytophysiognomy mosaic in the Poconé Pantanal region, state of Mato Grosso, Brasil. Seven units were studied for landscape, located within a 25 km(2) collection area, formed by thirty 250-m transects, at 1-km intervals in a 5 × 5 km area. Five collection points were marked in each transect at 50-m intervals, totaling 150 points. A collection was made at each sampling point with mini-Winkler extractor and pitfall traps. Using the mini-Winkler extractor, 1,088 individuals were collected distributed in 20 genera and 55 species, with Solenopsis invicta Buren and Pheidole (gr. biconstricta) sp.1 as the most frequent ants. Using pitfall traps, 2,726 individuals distributed in 24 genera and 48 species were sampled and Dorymyrmex (gr. pyramicus) sp.1 and Pheidole (gr. biconstricta) sp.1 were the most frequent species. A significant difference between the methods was observed in measured species number. The Principal coordinates analysis discriminated two species groups exclusively sampled by the mini-Winkler extractor and another by the pitfall methods. Therefore, it was concluded that these methods were complementary for ant diversity inventories in the Poconé Pantanal region.

This first survey of the ant fauna in a children's hospital in the city of Palmas, state of Tocantins, compares species composition, abundance and infestation rate of ants between rainy and dry seasons, day and night periods, and among 15 hospital sectors. Forty-eight collections, being 12 diurnal and 12 nocturnal in each season using five attractive baits distributed per sector, maintained for 3h per sampling. A total of 34,309 ants were collected, distributed in 12 species: Acromyrmex sp., Brachymyrmex sp., Camponotus spp. (four morphospecies), Dorymyrmex sp., Tetramorium sp., Solenopsis globularia (Creighton), Solenopsis saevissima Smith, Tapinoma melanocephalum (Fabricius) and Paratrechina longicornis (Latreille). The hospital presented an average building infestation rate (40.3%), when compared with hospitals from other Brazilian regions. In general, there was no difference in the species composition between seasons and the period of the day, although abundance of ants was higher at night. The dry season and the nocturnal period showed the highest infestation rate, mainly by T.melanocephalum and S.globularia. Gynecologic ward, lactation unit, preconception and pediatric ward access ramp showed higher infestation rate, although these varied between seasons. The significant infestation levels by the three species above, especially in sectors with restricted access such as lactation unit, laboratory, Intensive Care Unit e surgery center, indicate potential risks for contamination of patients by multi resistant pathogens possibly present in ants' bodies, as verified in others studies.

Ants (Hymenoptera: Formicidae) in a hospital in the city of Luz, Minas Gerais, Brazil. Urban ants, when present in hospital environments, can be a potential danger to public health, because they can carry pathogenic organisms and are possibly directly associated with the hospital cross infection problem. During a one-year period, collections were carried out, using non-toxic baits in a hospital of Luz, Minas Gerais State. The samples were distributed in 16 sites, being three outside and the others inside the hospital. Ants were found in 15 of the 16 sampled points. The most abundant genera were Brachymyrmex e Tapinoma, recorded inside and outside the hospital. The Camponotus genus was present as well, and generally collected where food was available (such as kitchen, rooms, refectory and garbage packing places) and structural failings on walls. Wasmannia, Pheidole, Linepithema, Monomorium, Dorymyrmex, Solenopsis and Paratrechina were also collected, totaling ten genera. Our results indicate a possible implication of the precarious condition in the hospital structure and the importance of cleaning in these environments.

O principal objetivo do estudo foi avaliar a taxa de exploração de iscas vivas por formigas em um Ambiente de Mata e de Campo de Gramíneas. O experimento foi desenvolvido no Pantanal sul-mato-grossense, no Município de Corumbá, MS, no período de outubro a novembro de 2006. Cupins do gênero Nasutitermes, serviram de iscas. Em cada área, 80 indivíduos dessa espécie permaneceram expostos no solo sobre uma base de papel filtro durante 10 Minutos. Observou-se a presença de 15 morfoespécies pertencentes a seis gêneros e cinco subfamílias, sendo mais freqüente Myrmicinae. No campo de gramíneas ocorreram maior riqueza e diversidade de espécies. Wasmania sp.1 foi responsável pelo maior número de iscas removidas na Mata e Dorymyrmex sp. 1 no Campo de Gramíneas. A diferença no tempo médio para remoção das iscas nas duas áreas (mata e gramínea) não foi significativa. Das 160 iscas oferecidas durante o experimento, 115 sofreram atacadas por formigas: 69 na mata e 46 no campo de gramínea. Activity of Ants (Hymenoptera: Formicidae) Foraging in a Forest Patch and in a subtropical seasonally flooded lowland grassland in the Pantanal from Mato Grosso do Sul, Brazil.Abstract. The main goal of this research was to evaluate the exploitation rate of live baits for ants in an environment of forest patches and subtropical seasonally flooded lowland grassland. The samples were collected from October to November 2006 in the Pantanal, sub-regions Miranda and Abobral, municipality of Corumbá, Mato Grosso do Sul, Center West Brazil. Termites of the genera Nasutitermes were used as bait, and remained exposed for 10 minutes on the soil. Eighty baits were used in each environment. Fifteen ant morphospecies in six genera and five subfamilies were collected, and the Myrmicinae were the most frequent subfamily. We found larger richness and diversity of species in the subtropical seasonally flooded lowland grassland. Wasmania sp.1 was responsible for the largest number of removed baits (30) in the Forest Patch and Dorymyrmex sp. 1 in the subtropical seasonally flooded lowland grassland. The difference in the average time for removal of the baits from the two areas was not significant. From the 160 baits offered during the experiment, 115 were attacked by ants, 69 in the Forest Patch and 46 in the grassland.

The spatial structure of habitats contains physical barriers that restrict the performance of diverse behavioural tasks. In heterogeneous habitats, information acquisition may allow animals to improve the performance of diverse activities such as foraging and locomotion. Nonetheless, changes in locomotion performance and their effects on the foraging success of animals have been scarcely studied. We examined these relationships in the harvester ant Dorymyrmex goetschi (subfamily Dolichoderinae) under laboratory conditions. In an experimental arena, we offered a food patch located at a fixed distance from the nest entrance. Landscape heterogeneity was created using wooden cubes arranged in different types of spatial distribution. We video recorded the behaviour of different colonies and quantified the number of active foragers, number of head contacts per capita per inbound trip, path length by workers that transported a food load from the resource patch to the nest, time invested in inbound travels, and the number of prey captured per colony. During the initial phase of patch exploitation, the number of foragers and prey captured were significantly lower than during the half and final phases of the experiment. Landscapes with greater spatial heterogeneity increased travel time and diminished locomotion velocity. A multiple regression analysis revealed that greater antennal contacts and locomotion velocities increased prey removal. Therefore, in this study, we documented a formal link between variables that characterize the movement paths of individuals and the foraging success of a colony. Information transfer between individuals generated a collective work with a concomitant improvement of food exploitation.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:40:47Z No. of bitstreams: 1 S1516-89132004000500017.pdf: 62435 bytes, checksum: b0d087f16a66d73441bdfccf1bbf6da8 (MD5) Made available in DSpace on 2013-08-22T18:40:47Z (GMT). No. of bitstreams: 1 S1516-89132004000500017.pdf: 62435 bytes, checksum: b0d087f16a66d73441bdfccf1bbf6da8 (MD5) Previous issue date: 2004-09-01 Made available in DSpace on 2013-09-30T19:26:52Z (GMT). No. of bitstreams: 2 S1516-89132004000500017.pdf: 62435 bytes, checksum: b0d087f16a66d73441bdfccf1bbf6da8 (MD5) S1516-89132004000500017.pdf.txt: 20007 bytes, checksum: 4f991a08477611dd0f136d370195e045 (MD5) Previous issue date: 2004-09-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:07:30Z No. of bitstreams: 2 S1516-89132004000500017.pdf: 62435 bytes, checksum: b0d087f16a66d73441bdfccf1bbf6da8 (MD5) S1516-89132004000500017.pdf.txt: 20007 bytes, checksum: 4f991a08477611dd0f136d370195e045 (MD5) Made available in DSpace on 2014-05-20T15:07:30Z (GMT). No. of bitstreams: 2 S1516-89132004000500017.pdf: 62435 bytes, checksum: b0d087f16a66d73441bdfccf1bbf6da8 (MD5) S1516-89132004000500017.pdf.txt: 20007 bytes, checksum: 4f991a08477611dd0f136d370195e045 (MD5) Previous issue date: 2004-09-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) A fauna de formigas predadoras presentes em lavouras de cana-de-açúcar localizadas no Estado de São Paulo, Brasil, foi avaliada utilizando-se iscas de sardinha. Plantas de três meses de idade foram utilizadas para a estimativa da fauna de formigas predadoras em duas usinas de cana-de-açúcar, usina São João e usina da Barra. Doze áreas [30m X 30 m (900 m²) cada] foram previamente delimitadas em cada usina para a coleta das formigas. As formigas foram amostradas colocando-se nove iscas no solo por área, sendo cada isca composta por um tubo de ensaio plástico (12 mm X 75 mm), contendo sardinha em seu interior. Na usina São João, a espécie de formiga predominante observada foi Solenopsis saevissima, seguida por Dorymyrmex sp. 1, Pheidole sp. 2, and Crematogaster sp. 1. Considerando apenas o gênero, os mais abundantes foram Solenopsis, Pheidole, Dorymyrmex e Crematogaster. Na usina da Barra, o gênero predominante amostrado foi Solenopsis, seguido por Pheidole, Crematogaster e Dorymyrmex. Como a predação por formigas predadoras generalistas deve ser uma das razões para os baixos níveis populacionais das infestações de Diatraea saccharalis em lavouras de cana-de-açúcar no Estado de São Paulo, este estudo ajudará futuras pesquisas destinadas a se conhecer as formigas predadoras que de fato agem como predadoras de ovos e estágios larvais iniciais de D. saccharalis no Brasil. Predaceous ant fauna present in natural sugarcane field plantations in the state of São Paulo, Brazil, was evaluated by using sardine baits sampling technique. Three-month-old sugarcane plants were used for ant fauna estimation in two sugarcane mills, São João and Barra Mill. Twelve 30m X 30 m (900 m²) plots were previously delimited in each sugarcane mill for ant sampling. Ants were sampled in each plot by placing nine sardine baits in 12 mm X 75 mm plastic tubes. In the São João Mill, the predominant ant species observed was Solenopsis saevissima, followed by Dorymyrmex sp. 1, Pheidole sp. 2, and Crematogaster sp. 1. Considering only ant genus, Solenopsis, Pheidole, Dorymyrmex, and Crematogaster, were predominant. In the Barra Mill, the predominant ant genus sampled was Solenopsis, followed by Pheidole, Crematogaster, and Dorymyrmex. As generalist predatory ants could be one of the reasons for the naturally low levels of D. saccharalis infestation on sugarcane in the state of São Paulo, this study could be helpful for the researchers to gain knowledge about the fauna of predaceous ants which acted as predators of eggs and early larval stages of D. saccharalis in Brazil. Universidade Estadual Paulista Instituto de Biologia Departamento de Parasitologia Universidade Estadual Paulista Instituto de Biologia Departamento de Ecologia Universidade Estadual Paulista Instituto de Biologia Departamento de Parasitologia Universidade Estadual Paulista Instituto de Biologia Departamento de Ecologia

Locomotion velocity during foraging activities is determined by factors such as travel distance, habitat structure and load mass among others. However, few studies on foraging behavior have analyzed the influence of spatial heterogeneity and food transportation on the locomotion velocity of ants under natural conditions. In order to study the mentioned factors, we selected 20 nests of the ant Dorymyrmex goetschi (subfamily Dolichoderinae), in a lower Andes locality of central Chile. Half of the nests were offered a food patch located at 10 cm from the nest entrance, and at 20 cm for the other half. We measured the duration of trips between nest and food patch and vice versa, and the distances traveled. We also recorded spatial heterogeneity of the substratum and soil temperature. Temperature was used as a covariate in the statistical analysis. Travel speed was significantly slower when worker ants returned to the nest with a food load, compared to the velocity of foragers without load that traveled from the nest to the patch. When the food patch was located at greater distance, locomotion velocity was significantly faster. Spatial heterogeneity did not affect movement speed. The reduction in locomotion velocity in ants carrying a load of 5.6 mg represents an energetic cost of transportation equivalent to 79% of the costs involved in moving a body mass of 1.6 mg. Faster velocities at larger patch distances can be interpreted as a strategy to maintain an efficient resource exploitation, by way of decreasing the time exposed to higher predation risk.

We examined habitat disturbance, species richness, equitability, and abundance of ants in the Fall-Line Sandhills, at Fort Benning, Georgia. We collected ants with pitfall traps, sweep nets, and by searching tree trunks. Disturbed areas were used for military training; tracked and wheeled vehicles damaged vegetation and soils. Highly disturbed sites had fewer trees, diminished ground cover, warmer soils in the summer, and more compacted soils with a shallower A-horizon. We collected 48 species of ants, in 23 genera (141,468 individuals), over four years of sampling. Highly disturbed areas had fewer species, and greater numbers of ants than did moderately or lightly disturbed areas. The ant communities in disturbed areas were also less equitable, and were dominated by Dorymyrmex smithi.

The transfer of nutrients between organisms is a common feature of mutualism. The production of these food rewards is often assumed to be costly. Estimation of the costs of producing food rewards is important for understanding the overall effects of the interaction on fitness. When food rewards are harvested by several species differing in foraging behavior, costs to the producer may differ. The larvae of many species in the butterfly family Lycaenidae produce secretions consumed by tending ants. Here I report that three North American ant species, Formica perpilosa, Dorymyrmex sp. (smithi complex), and Forelius foetida, had no negative effect on the duration of development and adult size of the lycaenid Hemiargus isola. Moreover, tending by the ant Formica perpilosa significantly enhanced larval growth, resulting in butterflies that were 20% heavier than their untended counterparts. Tending by the ants Dorymyrmex sp. (smithi complex) and Forelius foetida had no effect on butterfly weight. Tended, nonfeeding larvae lost 69% more weight than untended, nonfeeding larvae. Taken together, the results suggest that, although ant tending imposes a physiological cost, H. isola larvae use behavioral or physiological mechanisms to compensate or overcompensate for nutrients lost to ants.

An earlier study on the larvae of the Dolichoderinae was published by the authors in 1951. The present supplement contains descriptions of 9 additional species in the genera Dolichoderus , Forelius and Iridomyrmex . Forelius is new to the authors' collection and is characterized here for the first time. Necessary revisions are made in the 1951 descriptions and additional references to the literature are cited. The body profiles of dolichoderine larvae are classified into 3 generalized types; there is only 1 generalized type of mandible shape. The tubercles of 6 genera ( Dorymyrmex , Iridomyrmex , Bothriomyrmex , Engramma , Tapinoma, and Technomyrmex ) are described and contrasted with the tubercles of ponerine larvae, from which they differ markedly in number, position and shape.

Phosphorous—32 tracer studies of plant—arthropod food chains showed a significant difference in both consumer diversity and grazing pressure between the two dominant plant species on a first—year weed field in South Carolina. Where Heterotheca subaxillaris was the labeled plant 32P was transferred readily to a number of phytophagous insects and secondarily to the predator fauna. Where only Erigeron canadensis was tagged, there was little transfer of the isotope to the consumer populations, with the exceptions of the ant Dorymyrmex and the tree cricket Oceanthus. Dorymyrmex is a predator—scavenger, but also tends the aphids present on Erigeron; this latter habit accounted for the high uptake and unusual retention pattern of 32P by this ant where Erigeron was tagged. Oecanthus was primarily an herbivore, but the data suggest some predation on aphids from Erigeron plants. Very little 32P was transferred to the detritus eaters during the 43 day period of the study. Further support is given for the use of radi...

Most ant species are known to exhibit some degree ot patterning in oraging rate. Interspecific dif/erences in ]oraging rate can be noted both temporally and, in temperate latitudes, seasonally. Such dif/erences can contribute to an effective partitioning o resources among coexisting species. The ollowing seto observations documents a difference in oraging pattern that may be the significant component of coexistence ot the two closely competing species observed. The system will be described, and possible implicati.ons ot the observations will be discussed. The species observed wereDorymyrmex antarcticus and Tapinoma antarcticum , both members o the subfamily Dolichoderinae. Observations were made at Fundo Santa Laura, near Til Til, Santiago Province, Chile, during October and November o 97 and 972. The site was at ,ooo rn elevation on the east-acing slope o the low coastal cordillera. Vegetation was mixed shrubs and annuals orming the community known as matorral, which is characteristic o the Mediterranean climate zone o central Chile. On visits to the site in 97 I noted that the two species compete strongly or baits. A bait o honey on a small wad o cotton would attract Dorymyrmex antarcticus workers when it was placed on the ground in the early morning. These workers recruited a. small number o nestmates, and activity would continue until midmorning when the first ew workers o Tapinoma antarcticum appeared. These workers, once they located the bait, would quickly recruit many ot their nestmates, and the many small T. antarcticum workers aggressively repelled the ewer, la.rger, less aggressive workers o

The method differs from mammalian techniques for somatic chromosomes in that it uses very small amounts of material. Drosophila melanogaster and an ant, Dorymyrmex sp., are used as examples. Pretre...

Six dolichoderine species have haploid numbers: 9 (Iridomyrmex pilifer, I. sp. nr. pilifer, Dorymyrmex ?thoracicus, D. ?pulchellus), 13 (D. bicolor) and 16 (Forelius foetidus). Robertsonian changes could account for the differences between the Dorymyrmex numbers. The Iridomyrmex species, both Neotropical, have a different karyotype from Australian 9-chromosome Iridomyrmex. The species with numbers 13 and 16 have relatively more acrocentrics per karyotype than those with lower numbers. Five formicine species have haploid numbers: 8 (Oecophylla smaragdina), 9 (Brachymyrmex sp.), 15 (Lasius nearcticus), 21 (Polyrhachis rastellata), and 26 (Camponotus (Colobopsis) sp. (impressus gp.)). Although thelytoky has been reported for Oecophylla spp., a queenless greenhouse colony died out after producing an all-male brood; further work is suggested on Oecophylla populations where thelytoky has been reported. The 8- and 9-chromosome formicines have all chromosomes metacentric, while acrocentrics predominate in the higher-numbered species. The ponerine Proceratium silaceum has n = 18. Nine myrmicine species have haploid numbers: 10 (Pheidole dentata, P. dentigula), 11 Solenopsis molesta, Monomorium minimum, M. viridum, Meranoplus sp. (hirsutus gp.)), 12 (Leptothorax longispinosus), and 16 (Solenopsis aurea, S. geminata). Monomorium karyotypes have a small acrocentric, while all 11-chromosome Solenopsis chromosomes are metacentric. Reviewing the 92 known ant karyotypes supports some present taxonomic schemes but not others. Imai's (1966) suggestions, that polyploidy occurred in formicine evolution and that high numbers occur more frequently at 'high' latitudes, are not supported by present evidence.

Earlier studies with 32p have suggested that the old field ant (Dorymyrmex pyramicus), supposedly a predator and scavenger species, was feeding on horseweed (Erigeron canadensis). This supposition was based on an unusual pattern of 32p uptake in the ant population. The present investigation showed that Dorymyrmex is indeed a consumer of horseweed, accomplished not through herbivory, but instead by tending aphids present on these plants and ingesting honeydew. Ants confined for 7 days to tagged horseweed plants harboring aphids had over four times as much radioactivity as ants confined on tagged plants without aphids. The study suggests that the rapid rise and subsequent decline} of 32p in the ant populations in the field is characteristic of species with this food source. It may be a result of changes in the level of 32p in the phloem sap together with a bias in the sampling caused by collecting ants only from the vegetation.