Chemical Savants: The Role of Chemistry in Ants’ Survival, Communication and Ecology 

Jung Hao Cau, Luciana Chambilla Pastor, Fatima Janneh, Ya Lin

Abstract

Ants are ecologically dominant arthropods that possess a chemically intricate exoskeleton and venom system that supports their survival across various environments. Their exoskeleton, composed of chitin and proteins, provides protection and water resistance, while melanin pigments aid in thermoregulation and camouflage. Ants defend their colonies and prey using venom with antimicrobial properties, composed of peptides, alkaloids, and formic acid. Additionally, chemical reactions via pheromones enable the coordination of essential colony activities like foraging and defense. Finally, the role of ants as chemical architects is explored, highlighting how they modify soil structure, maintain symbiotic relationships with fungi, and utilize chemical secretions to manage their environments. These findings underscore the diverse biochemical adaptations of ants, contributing to their ecological success and significant influence within their habitats. 

Introduction

Ants are found across almost every single continent, they belong to the family Formicidae, and they have adapted to thrive in a wide range of environments from tropical forests to deserts (Fig. 1). Ants play crucial roles in ecosystems, such as soil aeration, seed dispersal, and organic matter decomposition, which makes them significant contributors to the ecosystem’s health. 

Fig 1. This map highlights various regions where the world’s 15,000 ant species and subspecies roam. This visually demonstrates their adaptability to diverse environments like tropical forests, deserts, grasslands, and urban areas (Normile, 2015).   

Beyond their ecological contributions, ants exhibit biochemical adaptations that have allowed them to survive and thrive in various habitats. Ants have skeletons on the outside of their bodies, referred to as exoskeletons. This exoskeleton protects the ant’s inner organs and muscles from damage. The biochemical composition of the ant’s exoskeleton protects the ant’s organs; it is a tough and flexible material that provides defense against its environment. It is chemically fortified to enhance its strength and flexibility and enables ants to carry out complex tasks such as foraging and nest building (Solano, 2014). Furthermore, ants use venom for defense against predators, immobilization of prey and interspecies competition. Their venom is a complex mixture of molecules and compounds that have specific roles that vary depending on the ant species. In addition, ants utilize pheromones, which are chemical substances that are created by organisms and emitted into the environment to influence the behavior or physiology of other members of their species (Wysocki & Preti, 2009). Ants utilize these substances to communicate and coordinate activities that allow them to work in perfect harmony to accomplish complex tasks. Overall, the chemical adaptations of ants are not only crucial for their survival, but it also has effects on ecosystem health. By understanding these interactions, we gain insight into how ants influence and sustain their environments with chemistry.

Chemical composition of ant exoskeleton 

The exoskeleton is composed of several layers primarily made of chitin, with certain areas being reinforced by the addition of minerals or hardened proteins that enhance rigidity. 

Chitin is a tough fibrous polymeric sugar and is one of the most abundant polysaccharides in nature, making it the most used material to increase strength in animals. This enhanced strength is due to the molecular structure of chitin (Fig. 2), which allows it to organize into crystalline structures and form nanofibrils. 

Fig. 2 Chemical structure of chitin, a polymer composed of N-acetylglucosamine (GlcNAc) (Sezer, n. d.). 

Chitin is a polysaccharide composed of repeating units of N-acetylglucosamine (GlcNAc), a derivative of glucose. Each unit is linked by glycosidic bonds (covalent β-(1→4)-linkage) and from long chains. This structure allows for the formation of strong hydrogen bonding between the nitrogen atom in the amine group of one GlcNAc unit and a hydroxyl group (-OH) on an adjacent chain, allowing the formation of nanofibrils (Moussian, 2019). 

Protective nature of the cuticle 

The cuticle covers the outer surface of the ant exoskeleton and acts as a protective barrier against harmful environmental factors. It is a tough and flexible material that provides defense against damage, dehydration, and environmental threats, such as changes in temperature. It is divided into several layers of tissues; the main ones being displayed in Fig. 3.  

Fig. 3 Schematic of arthropod cuticle structure. The cuticle (a) has 3 main layers of tissue, notably: (b) the epicuticle, (c) the exocuticle, and (d) the endocuticle. It is situated above the epidermis (e) where dermal glands are situated (f). The cuticle also has ducts that give an opening for glands (g) (modified from Encyclopedia Britannica, 2024). 

The top layer of the cuticle, the exocuticle, is pigmented due to the presence of melanin, the primary pigment in animals and insects. Melanin comes in two main types: eumelanin, which produces very dark brown and black colors, and pheomelanin, which gives reddish and yellowish colors. Both types are produced through a series of chemical reactions, as seen in Fig. 4, beginning with the transformation of amino acid L-tyrosine and  catalyzed by the enzyme tyrosinase present in the cuticle. This process both hardens and darkens the insect’s cuticle (Solano, 2014). 

Fig. 4 Synthesis of melanin. A series of reactions that start with L-tyrosine, which is then converted to dopamine. The intermediate is acetylated to N-acetyl–dopamine and is then oxidized to N-acetyl-dopamine quinone, resulting in melanin (iGem, 2020). 

The pigmentation of the cuticle in ants contributes to the protection of the insect in different ways, one being camouflage. Ants with reddish or light brown pigmentation use it to blend into their environment to avoid predators. In some species, pigmentation also contributes to catching prey by allowing ants to remain hidden until they strike (Bankar et al., 2024). In black ants, the cuticle’s color also plays an important role in thermoregulation and UV radiation protection (Bankar & al., 2021). This is because melanin absorbs sunlight. In cool environments, it helps to maintain optimal temperature for essential bodily functions. Furthermore, melanin’s capacity to absorb and scatter UV radiation is especially important to protect ants from cellular damage in their internal organs and tissues. Ultraviolet rays can cause a harmful chemical reaction within cells that produce reactive oxygen species (ROS), which causes damage to DNA, oxidative stress, inflammation, and cell apoptosis (Wei & al., 2024).  

Another property of the cuticle that protects the insect is the waxy cuticle layer, which is situated between the epicuticle and exocuticle (refer to Fig. 3). This is a waterproof layer made of hydrocarbons that covers the cuticle, which protects the ant from dehydration. Due to their small size and high surface area to volume ratio, ants are prone to desiccation, so the wax layer is essential. The cuticle’s hydrocarbons are long-chain molecules, formed of 21 to 40 carbon atoms. They vary in structure, some being straight chained alkanes, others methyl-branched, or unsaturated hydrocarbons (Ginzel & Blomquist, 2016). They are non-polar molecules, thus they do not interact with water and create a hydrophobic layer preventing water from leaving internal tissues (Ginzel & Blomquist, 2016).  

This layer is especially important for ants living in dry environments, such as desert ants, which must adapt physiologically to these areas. A major disadvantage for ants is that they are exposed to soil particles, which wear down the cuticle and increase water loss (Johnson, 2000). 

A study was done in the Department of Biology in Arizona State University to quantify water loss across several common desert ants and investigate how water loss rates differ depending on what role ants have in the colony (workers, males, and females) (Johnson, 2000). The study focused on these three species of ants: genera Aphaenogaster, Messor, and Pogonomyrmex, all in the subfamily Myrmicinae. Those ants live in arid environments where water conservation is crucial for survival. The water loss rates are measured and compared among workers, winged males, and winged females. The impact of soil abrasion was also studied by comparing the water loss rates of worker ants that have been exposed to soil during nest excavation, and those that have not been exposed.  

Fig. 5 (a)Water loss rate (μg h⁻¹ cm⁻² Torr⁻¹) and (b) percent water loss of initial wet mass over 8h at 30°C for live ants in the genera Aphaenogaster, Messor and Pogonomyrmex. Caste differences within each species are indicated by the letters a, b, c, d: a>b>c>d; asterisks denote significance level among castes after correcting P-values (Johnson, 2000).  

The results of the study, shown in Fig. 5, show that within a single species, water loss rates (WLR) follow a pattern. Worker ants tend to have higher WLR, males with intermediate levels of WLR and winged females having the lowest. Previous studies hypothesize that this significant difference between workers and winged females is due to adaptive differences, with winged females having a greater selective pressure to minimize water loss. However, this study found that workers and newly mated females have similar WLRs, disproving the hypothesis. This study suggests that it is due to cuticle abrasion from the soil. Exposure to soil seems to significantly affect water loss rates. This aligns with the fact that soil abrasion damages the waterproof wax layer of the cuticle and decreases hydrocarbon surface density (Johnson, 2000).  

Muscle attachments in the exoskeleton’s cuticle 

In arthropods, the exoskeleton plays a mechanical role in muscle attachment, and it is primarily due to the structural properties of the chitin molecule, which allow it to form strong bonds with other molecules, such as proteins.  These chitin-protein bonds happen within the cuticle. Chitin nanofibrils are bound to cuticle proteins (CPs) to create a rough structure that can withstand mechanical stress (Campli et al., 2024).  

As they mature, ants go through a process called moulting. This biological process is common in arthropods and consists of shedding the exoskeleton to form a new one. It is essential for all species of ants, since the outer parts of the exoskeleton do not grow with the insect. During this process, muscle reattachment to the exoskeleton is important for all arthropods. When the new cuticle forms, there are some epidermal cells, tendon cells (Fig. 6), which are responsible for connecting the tissues of the cuticle by secreting fibrils, the microtubules inside the tendon cells. These fibrils are inserted in the cuticle’s chitin-protein matrix and ensure that muscles remain attached throughout the process. Certain specific clotting proteins manage the connection between the exoskeleton and the tendon cells (Campli et al., 2024). 

Fig. 6 A schematic of the general structure of the muscle attachment to the epidermis in arthropods. Different parts of the structure include the myofilaments (Mf), microtubules (Mt), basal adherens junction (bAj), apical adherens junction (aAj), and intracuticular fibers (icF) (Znidarsic et al., 2012). 

Ant’s exocrine system

While the main purpose of the exoskeleton is protection, ants possess a complex exocrine system inside their exoskeleton consisting of glands that produce and release chemical compounds, including venom, pheromones, and antibiotics (Billen & Morgan, 2019). These glands are found in various locations in the ant’s anatomy, including the thorax, legs, tergal and sternal regions, and mandibles, as shown in Fig. 7 (Wang et al., 2021). 

 Fig. 7 Common exocrine glands of ants are shown in this schematic profile drawing of an ant. Venom glands produce venom. Mandibular, Dufour’s, pygidial, and venom glands produce pheromones. The metapleural gland produces antibiotics (Vander Meer, 2012). 

The chemistry of ant venom 

Mechanisms of ant stings and venom delivery 

Ants deliver venom through stings and produce complex biochemical compounds that are essential for survival. Approximately 71% of ant species are capable of stinging, while other subfamilies like Formicinae and Dolichoderinae do not sting. Venom delivery mechanisms vary, some ants sting directly while others have evolved to spray venom as an alternative. In Formicinae ants this spray can cover a wider area, affecting multiple targets or repelling predators without direct contact (Touchard et al., 2016). 

Fig. 8 Three venom-dispensing methods observed in M. Symmetochus. (A) Gaster flagging has the ant vibrating its gaster at a 45-degree angle with a drop of alkaloid venom at the tip and venom is dispersed into the air. (B) In Side-swipe the ant swings its gaster sideways towards the host and dispenses the venom directly onto the host ant. (C) Gaster-tuck sting occurs when the gaster is tucked between the legs to dispense venom directly onto the host ant (OSU Bio Museum, 2017).   

Additionally, ants such as Megalomyrmex symmetochus have developed specific behaviors to apply their venom. During aggressive interactions, these ants use methods like “gaster flagging,” (Fig 8; A) where they disperse venom into the air as a warning. They use “sideswipe” (Fig. 8; B) and “gaster-tuck sting” (Fig. 8; C) to inject venom directly onto a target with precision (OSU Bio Museum, 2017). Some ants also bite because they use their mandibles to grasp and secure their target before injecting venom through their stinger. This coordinated action ensures that the venom is delivered efficiently to immobilize or repel threats (Chen & Du, 2022). 

Chemical complexity of ant venom 

Ant venom is a complex mixture that consists of proteins, enzymes, biogenic amines, peptides, hydrocarbons, formic acid, and alkaloids (Aili et al., 2014). Venom is often designed to produce effects ranging from pain and paralysis to antimicrobial protection. Each component of ant venom serves a specific role that contributes to the ant’s survival, and the mixture of components varies significantly between species (Fig. 9). 

Fig. 9 A chart showing the different proportions of the type of venom ants use across species and demonstrates how venom composition varies according to the ecological traits of each ant (Touchard et al., 2024). 

Peptides are among the most prominent compounds in ant venom. The peptides found in ant venom have been identified with cytolytic properties, which means they use chemical mechanisms to induce cell death. Two common venom peptides named M-Tb1a and M-MYRTX-Tb2 create small and large pores in cell membranes that eventually lead to cell lysis, and they also damage the mitochondria by causing it to swell and break down (Ascoët et al., 2023). Additionally, a similar peptide called poneratoxin found in bullet ants (Paraponera clava) targets sodium ion channels in neurons which causes prolonged and excruciating pain that can be compared to being shot with a bullet (Robinson et al., 2023). This mechanism ensures that any potential predator experiences significant pain and deters further attacks.  

Formic acid is another prominent chemical in ant venom. This molecule is the simplest carboxylic acid (Fig. 10) and is abundant in the venom of Formicinae ants. The name “formic acid” originates from the Latin word “Formica” which means “ant”, because it was first discovered through the distillation of ants (American Chemical Society, 2022). Formic acid can constitute up to 70% of venom in some species, and it acts both as a defensive chemical as it deters predators by causing pain and it also acts as a pheromone (Touchard et al., 2016). It is synthesized in the glands through biochemical pathways. First, serine is converted into glycine to donate its alpha carbons to the reaction. Then cyclohydrolase catalyzes the pathway of several tetrahydrofolate derivatives, acting as intermediates to form 10-formyl-tetrahydrofolate. Next, 10-formyl-tetrahydrofolate  is catalyzed by a synthetase enzyme to release formic acid and regenerate tetrahydrofolate. This reaction also generates ATP which is used to transport formic acid into the venom gland reservoir (Hefetz & Blum, 1978). 

Fig. 10 The structure of formic acid is the simplest carboxylic acid which contains 2 oxygen atoms, a single carbon atom, and 2 hydrogen atoms (Unacademy, 2022). 

Alkaloids are organic compounds that contain nitrogen atoms which are significant components in fire ant venom. Red imported fire ants (Solenopsis invicta) have high alkaloid content which is responsible for the burning sensation that follows a sting with fire ant stings (Chen, 2023). The toxicity of the venom is influenced by the length of the side carbon chains and the ratio of saturated and unsaturated alkaloids. The relationship between side chain length and toxicity depends on the target organism. For instance, the venom of tropical fire ants (Solenopsis geminata) contains high concentration of piperidine alkaloids with a 11-carbon side chain is more toxic to caterpillars than the venom of red imported fire ants which has lower concentrations of these alkaloids (Xu & Chen, 2023).  

Production and secretion of venom 

The production of venom in ants involves specialized glands that are within the ant’s abdomen (shown in Fig. 7). The biosynthetic pathways that produce formic acid and alkaloid occur in the secretory portion of the gland with the help of enzymes. These secretory glands are composed of elongated and convoluted tubes that secrete venom, which is then stored in a reservoir connected to the stinger. The reservoir is lined with a thick cuticle that acts as a barrier against autolysis (self-digestion) of the ant. Next, the venom is transported to the excretory duct which is responsible for transporting venom to the sting and into the target (Ortiz & Mathias, 2005). When an ant stings, the muscles within the wall of the excretory duct control the ejection of the venom from the reservoir through the stinger and into the target (Aili et al., 2014; Ortiz & Mathias, 2005). The amount of venom produced ranges from 10 μg to 300 μg per individual. Unlike larger venomous animals, ants produce venom in tiny quantities, yet this is sufficient to induce pain in much larger animals (Touchard et al., 2016). The effectiveness of this mechanism can be seen in species like Solenopsis invicta, which can deliver up to 130 μg of venom in a single sting (Aili et al., 2014). 

Ecological roles of ant venom 

The chemical composition of ant venom plays a significant role in the ecology of ants. Primarily, it serves as a defense mechanism to protect ants from predators such as vertebrates and it provides a means for ants to attack prey (Aili et al., 2014). Some ant species use their venom to aggressively establish territories by driving away competing species. This has allowed this species to spread to new environments, where they often outcompete native species and become invasive (Chen, 2023). Similarly, the Pachycondyla tridentata ants use their venom to paralyze prey and employ a foaming release mechanism as a defensive strategy against other small ants (Aili et al., 2014).  

However, venom is not only used in confrontations. Some ants, such as leaf-cutter ants (Atta cephalotes), use chemical secretions to maintain the health of their colonies by sterilizing their environment. The venom they produce has antibacterial properties that help protect their food sources and nesting areas from contamination (Chen & Du, 2022). Additionally, the Lasius neglectus ants apply their venom onto their larvae to protect newborns from harmful pathogens and maintain colony health (Touchard et al., 2016).  

Ant pheromones & communication 

As superorganisms, ants must work together and coordinate colony activities, like transporting large objects, forming aggregations, and building nests. This requires inter-communication, which ants primarily facilitate using chemical signals called pheromones. Pheromones serve many functions, from exploratory and raid pheromones to alarm signaling and social structure indicators. Trail pheromones are important in enabling colonies to acquire food consistently and successfully. They regulate colony foraging and resource acquisition through positive and negative feedback processes and interact with other information sources in a way that functions like a collective colony memory (Jackson & Ratnieks, 2006). 

Alarm and raid pheromones serve opposite functions. While the former triggers defensive behavioral responses to danger, the latter coordinates offensive group attacks in the presence of prey (Jackson & Ratnieks, 2006). As ants can identify each other from pheromones found on the surface of their bodies (cuticular hydrocarbon pheromones), these pheromones direct behavior and maintain colony cohesion, ensuring a clear-cut colony hierarchy (Vander Meer & Alonso, 2019). 

The chemistry of pheromones 

The chemical compositions of pheromones can vary widely. Produced and detected in quantities ranging from nanograms to picograms, pheromones can consist of single compounds or complex blends, including hydrocarbons, terpenes, indole bases, and other organic compounds, shown in Fig. 11 (Hefetz, 2007). Despite serving the same functions, different ant species and subfamilies use different compounds as trail and alarm pheromones. Jet ants (Lasius fuliginosus) use carboxylic acids as trail pheromones (Huwyler et al., 1975), whereas Argentine ants (Linepithema humile) use iridoids (Choe et al., 2012) and leaf-cutter ants (Atta sexdens) use pyrazines (Morgan et al., 2006) (Fig. 11). To further illustrate this point, ants of the Myrmicine genera use 3-alkanones as alarm pheromones to signal danger, whereas members of the subfamily Dolichoderinae use methyl ketones (Blum & Brand, 1972).  

Among other factors, this biochemical divergence directly results from ecological adaptation, as certain chemical compositions of pheromones may be better suited to specific environments. For example, the proportion of 25- to 23-carbon chain compound cuticular hydrocarbons in insects increases at lower-latitude and higher-temperature environments because pheromones with higher proportions of carbon avoid desiccation and, therefore, require less frequent replenishing, as opposed to pheromones with less carbon content per molecule (Symonds & Elgar, 2008). 

Fig. 11: Examples of ant trail pheromone components found in venom reservoirs (Morgan, 2009). 

Ants’ exocrine system contains glands distributed across the body that produce and release chemical compounds, including pheromones (Billen & Morgan, 2019). Pheromones may originate from single glands or combinations of glands, such as the Dufour’s gland and venom gland, shown in Fig. 7 (Morgan, 2009). The pheromones produced and released from each gland are spatially optimized for their respective functions. For instance, glands which produce trail pheromones are often found in the hindlegs, which ensures the pheromones are dispersed directly onto the walking surface for others to detect and follow, as shown by sites 7 to 12 on the ant hindleg in Fig. 12 (Billen, 2009). Ants sense and respond to pheromones through a sophisticated olfactory system (i.e. detection by smell) (Hefetz, 2007). The primary olfactory center in ant brains is the antennal lobe, which contains specialized structures called glomeruli, essential for processing scents (Yamagata et al., 2006). 

Fig. 12: The ant diagram highlights the various exocrine glands in the legs, with gland types differentiated by color. The distal tarsomeres are enlarged below for clarity (Billen, 2008). 

Since the chemical composition of pheromones varies significantly between different ant species, their biosynthetic pathways and precursors also differs. Isotope-feeding experiments have been used to discern the biosynthetic precursors to the pheromones. These involve introducing heavy isotope precursor molecules into an ant’s system, tracking the incorporation of those isotopes into pheromones, and using analytical techniques like mass spectrometry to determine whether the tested precursors are involved in the biosynthesis of the final pheromonal compounds (Silva Junior et al., 2018). 

These experiments on Serratia marcescens 3B2, pyrazine-producing bacteria in the poison glands of the leaf-cutter ant (Atta sexdens rubropilosa), determined the biosynthetic precursors of trail pheromone pyrazines—L-threonine (Fig. 13). The researchers also proposed a possible biosynthetic pathway involving oxidation, reduction, tautomerization, and dehydration reactions, shown in Fig. 14 (Silva Junior et al., 2018). 

Fig. 13: Gas Chromatography/Mass Spectrectrometry chromatograms demonstrating the production of two types of pyrazine trail pheromones (1 and 2) by S. marcescens 3B2 cultivated on M9 agar medium supplemented with 0.2% of glucose and 2% of L-threonine in (A) and that observed in the presence of an Atta sexdens rubropilosa abdomen in (B) (Silva Junior et al., 2018). 

Fig. 14: Proposed biosynthetic pathway of two types of pyrazines produced by Serratia marcescens 3B2 (Silva Junior et al., 2018). 

Foraging trail pheromones 

Like most ants, leaf-cutter ants use more than one type of trail pheromone. Pharaoh ants (Monomorium pharaonis) use at least three types of foraging trail pheromones: a long-lasting attractive pheromone and two short-lived pheromones, one of which is attractive and the other repellent. The long-lived pheromones are less chemically volatile and persist for several days, whereas the short-lived pheromones are more volatile, lasting approximately 20 minutes. Altogether, pheromone trail systems function as a form of collective memory, allowing ant colonies to return to food-rich sites and avoid those that are depleted or unrewarding. The varying trail pheromones that differ in their persistence provide “memory” over differing time scales. To pharaoh ants, the long-lasting pheromone provides a longer-term memory, meaning that the trail network can be explored daily. On the other hand, sections of the network leading to food can be reinforced with the short-lasting trail pheromones. While the short-lasting attractive pheromone denotes routes to current food sources, the short-lasting repellent pheromone is a “no entry” signal to unrewarding branches in the network. As demonstrated in Fig. 15, this system is highly efficient as it allows ants to explore new locations consistently and swiftly decide between potential feeding locations (Jackson & Ratnieks, 2006; Morgan, 2009). 

Fig. 15 The colony’s stable trail network is marked with a long-lasting pheromone that spans its entire territory. Two short-lived pheromones guide ants to take the “best” branch at junctions. Once food is depleted, the attractive pheromone dissipates, and a no-entry pheromone is applied, closing off those routes. Similarly, unrewarding paths are also marked with repellent pheromones (Robinson, 2008). 

How ants use chemistry to defend, cultivate, and shape their soil ecosystems  

Ants, as highly organized and ecologically dominant social insects, have evolved intricate chemical mechanisms to interact with their environment. Among these mechanisms, the production and utilization of chemical compounds play a vital role in how ants maintain the health of their nests, manage relationships with beneficial organisms, and manipulate their surrounding soil. Ant species, particularly those like leaf-cutting ants (Atta and Acromyrmex), demonstrate complex chemical interactions, not only for colony defense but also in cultivating symbiotic fungi and modifying their soil habitats. This section explores three key aspects of ant chemistry: the antimicrobial secretions of the metapleural glands, the mutualistic relationships with fungi in leaf-cutting ants, and the broader impact of ant-driven soil modification. Together, these chemical processes highlight the unique ways ants influence their micro-environments, offering insights into their survival strategies and ecological engineering.  

The role of metapleural glands in ants   

The chemical interactions ants engage in are varied and complex, but one of the most vital tools in their arsenal is the metapleural gland, seen in the center of Fig. 7. Found uniquely in ants, this gland produces powerful antimicrobial secretions that protect the colony from harmful pathogens lurking in the soil (Beattie et al., 1986). By understanding the role of these secretions, we gain insight into the critical chemical defenses ants deploy to maintain their nests and overall colony health.  

To explore how destructive disinfection affects disease transmission within ants colonies, researchers created small nests with two chambers, each housing five ants. In one chamber, they introduced either an infectious sporulating pupa or a destructively disinfected, non-infectious pupa. The ants interacted with both types of corpses by grooming them, moving around, and spraying them with poison. For the infectious pupae, ants successfully removed all conidiospores, but the sporulating corpses still caused lethal, contagious infections in 42% of ants. Conversely, no disease transmission occurred from the destructively disinfected pupae, demonstrating that destructive disinfection prevents the pathogen from completing its lifecycle and stops disease transmission within the colony (Pull et al., 2018).  

Fig. 16 (A) Ants that interacted with sporulating pupae contracted lethal infections and died from fungal infection in 42% of the cases, whilst there was no disease transmission from destructively disinfected pupae. (B) Overview of normal fungal life cycle resulting in infectious, sporulating corpses (left) and a broken life cycle due to the interference of the ants (right). When sanitary care fails to prevent infection in pathogen-exposed individuals, the ants switch to colony-level disease control, that is destructive disinfection to stop pathogen replication, resulting in non-infectious corpses (Pull et al., 2018).  

There are a range of antimicrobial compounds in their metapleural gland. Two compounds found in these secretions are myrmicacin (3-hydroxydecanoic acid) (Fig. 17; A) and phenylacetic acid (Fig.17; C), both of which have been shown to play critical roles in controlling pathogen levels in ant nests.  

Fig. 17 Representative structures for compounds isolated from the metapleural gland of ants. A: myrmicacin (3-hydroxydecanoic acid); B: Indoleacetic acid; C: phenylacetic acid (Vander Meer, 2012).  

Myrmicacin’s primary mode of action involves disrupting the cell membrane integrity of microorganisms, which leads to cell lysis and death. Myrmicacin is particularly effective against fungal pathogens such as Alternaria spp. and Botrytis cinerea. When spores enter a dormant state, they can lie hidden within the ant colony, increasing the risk of fungal infection. By causing fungal spore germination, myrmicacin reduces the likelihood of fungal infections within the nest, thereby maintaining the health of the colony. This induction prevents spores from entering dormancy, initiating early germination. Myrmicacin can reduce the risk of fungal infection, as the spores become more vulnerable and are more easily eliminated by the ants’ hygienic behaviors or additional antimicrobial actions. Myrmicacin has antibacterial properties, particularly against gram-positive bacteria by disruption of the bacterial cell wall  (Vander Meer, 2012).  

Phenylacetic acid, another common compound found in mandibular gland secretions, plays a vital role in both inhibiting the growth of soil pathogens and promoting a more hygienic nest environment. It can specifically target soil fungi that might invade the nest or the ants’ food supply. By selectively disrupting fungal metabolic processes, it prevents infections and helps ants maintain their desired fungal gardens in species like leaf-cutting ants (Atta and Acromyrmex). Phenylacetic acid exhibits bacteriostatic properties, by interfering with their metabolic functions like protein synthesis and cell wall formation (Vander Meer, 2012). 

Ant-driven soil modification and ecosystem engineering  

Ants are renowned ecosystem engineers, significantly influencing the physical, chemical, and biological properties of the soil. Through their nest-building activities and chemical secretions, ants alter soil structure, nutrient composition, and microbial communities, which in turn affects ecosystem functions such as plant growth and nutrient cycling.  

Ant nest-building activities involve extensive soil excavation and tunneling, which can modify the physical properties of the soil. In the case of western harvester ants (Pogonomyrmex occidentalis), nests reduce soil bulk density from 1.54 g/cm³ in surrounding soil to 1.47 g/cm³ inside the nests, promoting water infiltration and retention (Frouz & Jílková, 2008).  

Ants not only physically modify the soil but also chemically alter it by depositing waste products and antimicrobial secretions into their nests. These secretions, including organic acids and antimicrobial peptides, change the pH and nutrient availability in the soil. The buildup of organic matter and nitrogen-rich compounds from food debris and ant excreta increases nutrient levels, especially nitrogen and phosphorus, in the nest soil.  

Ants often shift the soil pH toward neutral values, enhancing nutrient availability. For example, Lasius niger has been observed to increase soil pH in acidic environments by accumulating organic matter in the nest, as the material decomposes the basic cations are released into the soil, which makes nutrients such as phosphorus more accessible to plants (Fig. 18). In other cases, ants decrease pH in alkaline soils, improving the soil’s suitability for microbial activity and plant growth.  

Fig.18 Relationships between soil pH and the nest-soil difference in pH. Filled circles based on data from Lasius niger (Frouz & Jílková, 2008).  

The ecological impacts of ant-driven soil modification extend beyond the nest, influencing plant growth, soil fertility, and overall biodiversity. Ant nests often act as nutrient hotspots, with higher levels of nitrogen, phosphorus, and potassium, which enhance soil fertility and promote plant growth. Research has shown that leaf-cutting ants (Atta spp.) contribute significantly to nutrient cycling by collecting plant material, which is decomposed in their nests, enriching the surrounding soil with nutrients that are essential for plant development (Frouz & Jílková, 2008). Trees growing near Atta nests have been found to utilize these nutrients, showing increased growth and seed production compared to trees farther from nests.  

Ant nests often create microhabitats that support a diverse array of plant species and microorganisms. For example, harvester ants (Pogonomyrmex spp.) distribute seeds around their nests, influencing plant species composition and promoting higher biodiversity in their foraging areas (Frouz & Jílková, 2008). Additionally, the increased availability of nutrients and improved soil structure around nests support a rich microbial community, enhancing ecosystem resilience.  

Conclusion

Ants have remarkable chemical makeups and strategies that enable their survival and dominance in a broad range of environments. When living in extreme conditions like deserts, ants are at high risk of dehydration, overheating, and damage from UV radiation. Ants have adapted to reinforce their exoskeletons with a waxy layer of hydrophobic hydrocarbons and melanin-rich layers, which provide a water-repelling barrier to minimize moisture, subvert UV radiation, and regulate heat. Additionally, as small omnivorous insects, ants are vulnerable to predators and require prey-hunting strategies for sustenance. As a solution to both of these conundrums, ants developed venom as a chemical defense and predation mechanism. Often containing a blend of toxic peptides, alkaloids, and formic acid, ant venom disrupts cell membranes and deters larger predators by stinging or spraying. As superorganisms, ants must be able to communicate to coordinate complex colony-scale tasks. This is accomplished using volatile chemical signals called pheromones, which are secreted by various glands and detected by smell. Different compositions of pheromones are used to mark trails, warn of threats, or identify roles within the colony, allowing for precise context-dependent signaling and functioning as “chemical language” that adapts to varying environmental pressures. These chemical adaptations illustrate ants’ ability to design innovative solutions for survival, meeting the unique demands of their many ecosystems with creativity and efficiency. 

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