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The organic nature of wood makes it susceptible to abiotic and biotic degradation. Impregnation with chemical products is the most common method of protection. Only inorganic borates combine the unique set of properties that make them well suited for wood protection: they are insecticidal, fungicidal and flame retardants. In this work, zinc borate is suspended in an ammonia solution and applied in depth to wood. Its resistance to leaching is evaluated. The product is tested against rot fungi (Gloeophyllum trabeum and Trametes versicolor) and a xylophagous insect (Anobium punctatum). The results verify its effectiveness as a wood protector, while leaching less than other borate-based products. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2007.02.021 Byline: Martin Bollazzi, Flavio Roces Abstract: To investigate to what extent climatic variables are used by ant workers to decide whether and where nest building should be started, the effect of humidity content of the circulating air on building behaviour was studied in the leaf-cutting ant Acromyrmex ambiguus. In the laboratory, a colony was confronted with an experimentally induced circulation of either dry or wet air through its nest chambers, and the plugging of nest tunnels with leaf fragments was recorded as indicative building response. Results showed that circulating dry air triggered building responses. Tunnel plugs were constructed mostly in the inflows of dry air and to a much lesser extent in the outflows of dry air, indicating that the direction of the air movement inside tunnels spatially guided the workers' building behaviour. However, circulating humid air, or a passive loss of humidity from the nest, did not suffice to trigger tunnel plugging. Taken together, results showed that A. ambiguus workers use the direction of the airflow as an environmental cue for spatially guiding their building behaviour, yet workers only responded if the humidity content of the circulating air was low. These building responses seem to result from a compromise between the need of air renewal and the avoidance of unsuitable climatic conditions. To our knowledge, our results are the first in showing that ant workers respond to a specific climatic variable to decide whether and where a nest structure, related to the control of nest climate, should be built. Author Affiliation: Department of Behavioural Physiology and Sociobiology, University of Wurzburg, Germany Article History: Received 10 June 2006; Revised 29 January 2007; Accepted 2 February 2007 Article Note: (miscellaneous) MS. number: 8997R2

1. Leaf‐cutting ants remove copious amounts of colony waste, a potential pathogen source for workers and reared symbiotic fungus, to above‐ground heaps or deep underground chambers. However, the dumpsite may also contain information about plants initially harvested and disposed of because of unsuitability for the fungus. 2. The underground environment presents climatic gradients across the soil profile and it is an open question whether leaf‐cutting ants use microclimatic cues to choose suitable sites for waste disposal, as displayed for other in‐nest tasks. 3. Climatic preferences in leaf‐cutting ants were investigated for the deposition of colony waste. In the laboratory, deposition of waste particles by workers of Atta laevigata was quantified by offering them, in different experiments, a binary choice of temperatures (range, 15–30 °C), levels of air humidity (range 10–98%), and CO2 concentrations (range, atmospheric values to 10%). 4. Leaf‐cutting ants used temperature and air humidity, but not CO2 levels, as cues for the deposition of their waste. They consistently preferred a dry (≤ 33% air humidity) environment. Less consistent, temperature preferences varied depending on colony (15–25 °C for one colony and 25–30 °C for the other). Although workers showed clear preferences for high levels of CO2 for themselves, they were CO2‐indifferent for waste deposition. 5. It is argued that the observed climatic preferences for underground waste disposal might aid nest hygiene by providing unsuitable dry conditions for pathogen growth, with thermal preferences that do not hinder worker activities for further waste management and inspection of discarded plants. [ABSTRACT FROM AUTHOR]

To explore landscape genomics at the range limit of an obligate mutualism, we use genotyping‐by‐sequencing (ddRADseq) to quantify population structure and the effect of host–symbiont interactions between the northernmost fungus‐farming leafcutter ant Atta texana and its two main types of cultivated fungus. Genome‐wide differentiation between ants associated with either of the two fungal types is of the same order of magnitude as differentiation associated with temperature and precipitation across the ant's entire range, suggesting that specific ant–fungus genome–genome combinations may have been favoured by selection. For the ant hosts, we found a broad cline of genetic structure across the range, and a reduction of genetic diversity along the axis of range expansion towards the range margin. This population‐genetic structure was concordant between the ants and one cultivar type (M‐fungi, concordant clines) but discordant for the other cultivar type (T‐fungi). Discordance in population‐genetic structures between ant hosts and a fungal symbiont is surprising because the ant farmers codisperse with their vertically transmitted fungal symbionts. Discordance implies that (a) the fungi disperse also through between‐nest horizontal transfer or other unknown mechanisms, and (b) genetic drift and gene flow can differ in magnitude between each partner and between different ant–fungus combinations. Together, these findings imply that variation in the strength of drift and gene flow experienced by each mutualistic partner affects adaptation to environmental stress at the range margin, and genome–genome interactions between host and symbiont influence adaptive genetic differentiation of the host during range evolution in this obligate mutualism. [ABSTRACT FROM AUTHOR]

Defense against biotic or abiotic stresses is one of the benefits of living in symbiosis. Leaf-cutting ants, which live in an obligate mutualism with a fungus, attenuate thermal and desiccation stress of their partner through behavioral responses, by choosing suitable places for fungus-rearing across the soil profile. The underground environment also presents hypoxic (low oxygen) and hypercapnic (high carbon dioxide) conditions, which can negatively influence the symbiont. Here, we investigated whether workers of the leaf-cutting ant Acromyrmex lundii use the CO2 concentration as an orientation cue when selecting a place to locate their fungus garden, and whether they show preferences for specific CO2 concentrations. We also evaluated whether levels preferred by workers for fungus-rearing differ from those selected for themselves. In the laboratory, CO2 preferences were assessed in binary choices between chambers with different CO2 concentrations, by quantifying number of workers in each chamber and amount of relocated fungus. Leaf-cutting ants used the CO2 concentration as a spatial cue when selecting places for fungus-rearing. A. lundii preferred intermediate CO2 levels, between 1 and 3%, as they would encounter at soil depths where their nest chambers are located. In addition, workers avoided both atmospheric and high CO2 levels as they would occur outside the nest and at deeper soil layers, respectively. In order to prevent fungus desiccation, however, workers relocated fungus to high CO2 levels, which were otherwise avoided. Workers’ CO2 preferences for themselves showed no clear-cut pattern. We suggest that workers avoid both atmospheric and high CO2 concentrations not because they are detrimental for themselves, but because of their consequences for the symbiotic partner. Whether the preferred CO2 concentrations are beneficial for symbiont growth remains to be investigated, as well as whether the observed preferences for fungus-rearing influences the ants’ decisions where to excavate new chambers across the soil profile. [ABSTRACT FROM AUTHOR]

The article discusses a study on the thermoregulatory function of thatched nests made by the South American grass cutting ant, Acromyrmex heyeri. According to the study, the core temperature of the nest was higher than the environment, but remained below values harmful for the fungus. It further states that this thermoregulation of preventing diurnal nest overheating and avoiding losses of the accumulated heat in night was brought about by the low thermal diffusivity of nest made by leaves.

Leaf-cutting ant colonies largely differ in size, yet all consume O 2 and produce CO 2 in large amounts because of their underground fungus gardens. We have shown that in the Acromyrmex genus, three basic nest morphologies occur, and investigated the effects of architectural innovations on nest ventilation. We recognized (i) serial nests, similar to the ancestral type of the sister genus Trachymyrmex , with chambers excavated along a vertical tunnel connecting to the outside via a single opening, (ii) shallow nests, with one/few chambers extending shallowly with multiple connections to the outside, and (iii) thatched nests, with an above-ground fungus garden covered with plant material. Ventilation in shallow and thatched nests, but not in serial nests, occurred via wind-induced flows and thermal convection. CO 2 concentrations were below the values known to affect the respiration of the symbiotic fungus, indicating that shallow and thatched nests are not constrained by harmful CO 2 levels. Serial nests may be constrained depending on the soil CO 2 levels. We suggest that in Acromyrmex , selective pressures acting on temperature and humidity control led to nesting habits closer to or above the soil surface and to the evolution of architectural innovations that improved gas exchanges., (© 2021 The Authors.)

Social insects show temperature and humidity preferences inside their nests to successfully rear brood. In underground nests, ants also encounter rising CO 2 concentrations with increasing depth. It is an open question whether they use CO 2 as a cue to decide where to place and tend the brood. Leaf-cutting ants do show CO 2 preferences for the culturing of their symbiotic fungus. We evaluated their CO 2 choices for brood placement in laboratory experiments. Workers of Acromyrmex lundii in the process of relocating brood were offered a binary choice consisting of two interconnected chambers with different CO 2 concentrations. Values ranged from atmospheric to high concentrations of 4% CO 2 . The CO 2 preferences shown by workers for themselves and for brood placement were assessed by quantifying the number of workers and relocated brood in each chamber. Ants showed clear CO 2 preferences for brood placement. They avoided atmospheric levels, 1% and 4% CO 2 , and showed a preference for levels of 3%. This is the first report of CO 2 preferences for the maintenance of brood in social insects. The observed preferences for brood location were independent of the workers' own CO 2 preferences, since they showed no clear-cut pattern. Workers' CO 2 preferences for brood maintenance were slightly higher than those reported for fungus culturing, although brood is reared in the same chambers as the fungus in leaf-cutting ant nests. Workers' choices for brood placement in natural nests are likely the result of competing preferences for other environmental factors more crucial for brood survival, aside from those for CO 2 ., (Copyright © 2018 Elsevier Ltd. All rights reserved.)