Nest architecture development of grass-cutting ants

Insects

Acromyrmex fracticornis grass-cutting ants construct conspicuous chimney-shaped nest turrets made of intermeshed grass fragments. We asked whether turrets are constructed by merely piling up nearby materials around the entrance, or whether ants incorporate different materials as the turret develops. By removing the original nest turrets and following their rebuilding process over three consecutive days, age-dependent changes in wall morphology and inner lining fabrics were characterized. Micromorphological descriptions based on thin sections of turret walls revealed the building behaviors involved. Ants started by collecting nearby twigs and dry grass fragments that are piled up around the nest entrance. Several large fragments held the structure like beams. As a net-like structure grew, soil pellets were placed in between the intermeshed plant fragments from the turret base to the top, reinforcing the structure. Concomitantly, the turret inner wall was lined with soil pellets, star...

Sociobiology, 2014

Insectes Sociaux, 2004

The architecture of underground ant nests was studied in the ant Formica pallidefulva. These ants build shallow (30 -45 cm deep) nests, which consist of more or less vertical shafts that bear chambers. Shafts are modular units of nest growth; nests are enlarged by adding more shafts or extending previously existing ones. The nests are top-heavy, their volume declining exponentially with depth. The total volume of the nest is strongly correlated with the number of worker occupying the nest (R 2 = 0.87). Some of the rules and templates used by workers for nest construction were determined: (a) chambers are formed in the direction of the tunnels leading up to them, (b) the amount of soil excavated per unit time increases with soil temperature and moisture content. The amount of time and energy required to construct a typical nest were approximated using digging ability parameters determined in the lab. We estimate that if a colony was to move twice a year, it would expend around 20 % of its energy intake and at least 6 % of its worker time on nest excavation.

Sociobiology, 2015

Cyphomyrmex ants are a basal group of small fungus-growers (Myrmicinae:Attini), which differ profoundly from their most studied relatives Atta and Acromyrmex. Our objective was to investigate the nest biology and demography of the fungus-growing ant Cyphomyrmex lectus in a transitional area (savanna-forest) disturbed by an annual fire regime, in Southeast Brazil. The colonies of C. lectus were located close to each other (mean distance between nests, 3.38 ± 2.75 m). Its external nest structure consisted of a single circular nest-entrance hole but without a conspicuous nest mound. Nests were relatively simple consisting of a single well-formed chamber and a single gallery connecting to the nest entrance. No relationships were found between ant number per colony and gallery length, as well as chamber volume. Nonetheless, we detected an effect of the ant number per colony on chamber depth. In this sense, a deeper chamber could warrant a better protection against fire, natural enemies a...

Royal Society Open Science, 2020

Ants build complex nest structures by reacting to simple, local stimuli. While underground nests result from the space generated by digging, some leaf- and grass-cutting ants also construct conspicuous aboveground turrets around nest openings. We investigated whether the selection of specific building materials occurs during turret construction in Acromyrmex fracticornis grass-cutting ants, and asked whether single building decisions at the beginning can modify the final turret architecture. To quantify workers' material selection, the original nest turret was removed and a choice between two artificial building materials, thin and thick sticks, was offered for rebuilding. Workers preferred thick sticks at the very beginning of turret construction, showed varying preferences thereafter, and changed to prefer thin sticks for the upper, final part of the turret, indicating that they selected different building materials over time to create a stable structure. The impact of a singl...

PloS one, 2018

In social insects, nests are very important structures built to provide a protected microhabitat for immature development and food storage and are the places where most interactions between all members of a colony occur. Considering that nest architecture is an important behavioural trait that can clarify essential points of the social level of the species, here we describe the architectural model of the Ponerinae ant Odontomachus chelifer. Five subterranean nests were excavated; one of them filled with liquid cement for extraction of casts of chambers, shafts and tunnels. All nests were found in a woodland area, with Dystrophic Red Latosol soil, associated with roots of large trees and, differently from the pattern currently described for this subfamily, presented a complex structure with multiple entrances and more than one vertical shaft connected by tunnels to relatively horizontal chambers. The number of chambers varied from 24 to 77, with mean volume ranging from 200.09 cm3 to...

Journal of Insect Science, 2019

Nests are physical entities that give shelter to the inhabitants from natural adversities, predators and act as a platform for organization of tasks particularly in social insects. Social insect nests can range from simple structures consisting of a single entrance leading to a chamber to complex nests containing hundreds of connected shafts and chambers. This study characterizes nest architecture of a tropical ponerine ant Diacamma indicum (Hymenoptera: Formicidae), which has small colony sizes and is known to be a scavenger. We also examined if these nests vary seasonally. By examining the microhabitat in the vicinity of the nest, the nest entrance characteristics and casting 77 natural nests of D. indicum across a year, we found that this species occupies relatively simple nests consisting of a single entrance that leads to a single chamber. This chamber progressed to a secondary tunnel that terminated at a greater depth than the chamber. The nest volume was not correlated to the...

Annals of the Entomological Society of America, 2011

Fungus-growing ants (Formicidae: Attini) comprise a diverse and ecologically important group in Neotropical habitats. Compared with leaf-cutters, however, relatively little is known about the biology of less conspicuous attine species. Here, we compare nest size and structure, colony size and demographic composition, and worker size and polymorphism among the genera Cyphomyrmex, Mycetarotes, Mycocepurus, Myrmicocrypta, Sericomyrmex, and Trachymyrmex. In total, 25 ant colonies (one species per genus) were investigated at one site in the Brazilian savanna. Results indicate a consistent variation in nest size and structural complexity (architecture), colony and worker size, and a tendency to polymorphism among the studied genera. In addition, nest mound volume was found to be a good predictor of both worker number and volume of the fungus garden. Based on morphometric analyses, Sericomyrmex and Trachymyrmex together formed a distinct group from the other genera. The transition from the ancestral agricultural system toward the derived leaf-cutting habit also is followed by remarkable changes in nest size and architecture, colony size, and worker size and polymorphism. Our results support other recent studies that consider Sericomyrmex and Trachymyrmex as possessing transitional habits, distinct both from species that cultivate fungus by using mostly nonplant items (insect feces and corpses) as well as from typical leaf-cutters Atta and Acromyrmex. This is the Þrst study to detect correlations of nest traits with worker number and size of fungus garden in the less conspicuous attines. Results highlight the importance of combining data on natural history and morphometry to understand the evolutionary history of fungus-growing ants.

Psyche: A Journal of Entomology, 2012

Leaf-cutting ant workers dig underground chambers, for housing their symbiotic fungus, interconnected by a vast quantity of tunnels whose function is to permit the entrance of food (leaves), gaseous exchanges, and movement of workers, offspring, and the queen. Digging is a task executed by a group of workers, but little is known about the group effect and group-constructed functional structures. Thus, we analyzed the structures formed by worker groups (5, 10, 20, and 40 individuals) of the leaf-cutting ant, Atta sexdens rubropilosa, for 2 days of excavation. The digging arena was the same for the 4 groups, with each group corresponding to a different density. Our results verified a pattern of tunneling by the workers, but no chamber was constructed. The group effect is well known, since the 40-worker group dug significantly more than the groups of 5, 10, and 20. These groups did not differ statistically from each other. Analysis of load/worker verified that workers of the smallest group carried the greatest load. Our paper demonstrates the group effect on the digging of nests, namely, that excavation is proportional to group size, but without emergence of a functional structure such as a chamber.

Behaviour

Ants living in subterranean nests face the challenge of nest flooding and require to combat this recurring issue. The tropical Ponerine ant species, Diacamma indicum, living in simple nests with a single chamber, was used in the current study to examine mound building in the lab. Upon stimulating rain ( colonies) they built significantly larger nest mounds as compared to controls. Nest mounds proved to be important to colonies that had experienced rain while relocating. Relocating colonies showed significantly higher preference for new nests with mounds (12/13) when choosing between two equidistant, similar quality potential new nests in contrast to control relocations. To the best of our knowledge this study for the first-time documents mound building behaviour in any Ponerine species in laboratory conditions and introduces nest mounds as another architectural feature of interest to relocating colonies.

2011

Ant nests vary in their depth and internal complexity. They can be shallow or reach seven meters down into the soil, with many chambers connected by tunnels. In the case of leaf-cutting ants, the nest protects the colony and provides appropriate microclimate conditions for the ants and the symbiotic fungus garden. In the present study we compared the internal architecture and population size of Acromyrmex subterraneus molestans nests in an urban and a rural area. We excavated, molded and measured six nests in an urban area and five nests in a rural area. For each nest, we measured the total volume of fungus in the chambers and estimated the population by counting the workers, which were separated into four size classes. The nests of A. subterraneus molestans in the urban and rural areas were always found near the base of trees. In the urban area they were also found near the curb of sidewalks. Ants use old roots and debris to reinforce the structure of the nest tunnels and at the same time reduce the costs of excavation by taking advantage of pre-existing cavities. Nests from the rural area had only one chamber, whereas in the urban area they had up to four chambers. Fungus chambers showed non-defined shapes and were found near the soil surface, both in the urban and in the rural area. Closeness to the surface may pose a problem to the maintenance of the humidity levels required by the fungus garden. The accumulation of cut leaves over the nest, as observed for other species of leaf-cutting ants, in Sociobiology Vol. 58, No. 3, 2011 particular A. crassispinus, may be a strategy to solve this problem. Building superficial nests also helps reduce the costs of excavating, and saves energy in the transport of substrate to the fungus chamber. The nest tunnels were located in pre-existing cavities and almost always connected the external environment to the fungus chamber. There were also longer tunnels that opened at some distance from the nest. These tunnels allow an increase in the foraging area and reduce the risk of outside predation. With respect to population size, we noted that the small workers represented on average 50% of the population, with no difference between the proportion of workers of each size class between urban and rural nests. No significant differences were found in the volume of fungus between nests of the urban and rural area. There were no significant correlations between the volume of fungus and the total population of workers or the number of workers of each size class.

Revista Brasileira de Entomologia, 2021

Sociobiology, 2016

The nest dug by the leaf-cutter ant queen of the genus Atta is a vertical tunnel interconnected to a small chamber to hold its offspring and the symbiotic fungus. The depth of the initial chamber of the Atta sexdens rubropilosa ranges from 10 to 30 cm below the soil surface. This available information, could it be that the ideal initial nest depth is adapted to favorable conditions for the initial colony? We hypothesized this depth can provide a minimum temperature range with almost constant temperature, leading to the development of symbiotic fungus and brood yet to emerge. To test this hypothesis, laboratory experiments were carried out and the soil temperature was measured at different depths. The colony development at different temperatures was studied in the laboratory and the brood production (number of eggs, larvae, pupae and adults) was measured until the first workers emergency. Additionally, lipid content and the survival of queens at different temperatures were determined...

PLOS ONE, 2017

A host of animals build architectural constructions. Such constructions frequently vary with environmental and individual/colony conditions, and their architecture directly influences behavior and fitness. The nests of ant colonies drive and enable many of their collective behaviors, and as such are part of their 'extended phenotype'. Since ant colonies have been recently shown to differ in behavior and life history strategy, we ask whether colonies differ in another trait: the architecture of the constructions they create. We allowed Temnothorax rugatulus rock ants, who create nests by building walls within narrow rock gaps, to repeatedly build nest walls in a fixed crevice but under two environmental conditions. We find that colonies consistently differ in their architecture across environments and over nest building events. Colony identity explained 12-40% of the variation in nest architecture, while colony properties and environmental conditions explained 5-20%, as indicated by the condition and marginal R 2 values. When their nest boxes were covered, which produced higher humidity and lower airflow, colonies built thicker, longer, and heavier walls. Colonies also built more robust walls when they had more brood, suggesting a protective function of wall thickness. This is, to our knowledge, the first study to explicitly investigate the repeatability of nestbuilding behavior in a controlled environment. Our results suggest that colonies may face tradeoffs, perhaps between factors such as active vs. passive nest defense, and that selection may act on individual construction rules as a mechanisms to mediate colony-level behavior.

Although fire ants have been extensively studied, not much has been published about the structure and building material of their nests and even less on the lining of chamber walls. Nests built in unconsolidated sandy soils of Solenopsis electra and Solenopsis nr. macdonaghi, studied in La Pampa and Chubut (Argentina), respectively, show organic linings, which are reported herein for the first time. It is hypothesized that these organic linings may be of fecal origin, since there is no organic rich horizon in those soils. Apart from its significance as regards ant architecture and nest function, the presence of organic linings in ant nests is important for interpreting fossil nests, which have been often assigned to termites based on the presence of organic linings.