Unlocking Locust Survival: A Chemical Analysis of Locusts 

Frederic Koran, Claire Leader, Alexandra Stoilova, Alina Weng

Abstract

The complex chemical properties of locusts are responsible for the development, adaptability, and survival. Key factors such as hormones —including the juvenile hormone and [His7]-corazonin—and physiological functions enable the locust to respond to environmental cues. The juvenile hormone regulates growth and coloration, while neurotransmitters like dopamine and serotonin influence behavior and phase changes. Chemical communication, through pheromones and other signals, governs social interactions, reproductive synchronization, and swarm formation during both solitary and gregarious phases.  Understanding these chemical mechanisms provides insight into their function and place in the natural world and develop strategies for managing their impacts on agriculture and ecosystems. 

Introduction

Locusts, infamous for their destructive swarms, belong to the Acrididae family, which includes about 20 species known for phase transformations (phase polyphenism). This trait enables them to switch between two phases in response to environmental challenges: the solitary phase, where locusts behave more like individual grasshoppers, and the gregarious phase, in which they form swarms and are more attracted to other locusts. The environmental cues could be anything from population density to resource availability. While adaptability is behavioural, it goes further to chemical processes that regulate development, physiology, and interactions with the environment. 

One of the locusts’ most fascinating abilities is their capacity to thrive in diverse environments, from lush grasslands to arid deserts. By exhibiting specific chemical processes through experience, the locust can make these necessary adaptations for their survival. For instance, chemical signals influence whether offspring develop into solitary or gregarious forms, altering their physical traits and behavior without changing their DNA.  In the locust’s nymphal stages, hormones are central and direct their growth and maturation. The juvenile hormone, secreted by the corpora allata, an endocrine gland near the brain, regulates the timing of development.  A decline in juvenile hormone levels triggers molting and development of adult characteristics such as wings or reproductive organs (Riddiford, 2012). As you may imagine, any disruption in timing can lead to developmental abnormalities or premature maturation, so precise timing is essential. The hormone [His₇]-corazonin is a neuropeptide that drives pigmentation. [His₇]-corazonin and juvenile hormone work together to determine locust coloration, influenced by factors such as camouflage, predator avoidance, and ecological interactions (Pener & Yerushalmi, 1998). Their precise interaction is essential to proper and specific development of physical traits at the right time. 

Neurotransmitters like dopamine and serotonin play an important role in locusts’ behavioral and phase changes. Dopamine influences movement, arousal, and motivation of a locust and elevated dopamine levels are associated with increased locomotor activity and motivation, which promote social behaviors and swarming (which is a good thing for locusts) (Ma et al., 2011). Serotonin controls the sensory perception and behavior in locusts, promoting both solitary and gregarious phases depending on the species of locust (desert locusts react differently than migratory locusts). These chemical messengers drive the locust to adapt to its surroundings, changing based on specific conditions (Anstey et al., 2009).  

Body-colour polymorphism 

Life cycle of the locust 

The life cycle of a locust begins in the egg phase. Female locusts lay their eggs inside holes made of damp soil and sand called pods (Fig. 1). Mothers produce a frothy liquid that fully envelopes the egg, protecting it from dehydration and predators (Agriculture Victoria, 2024). Phase change has been shown to accumulate generationally through the froth; it contains water-soluble factors known as aggregation pheromones that have been shown to influence whether a locust will hatch gregarious or solitary. Hormones and epigenetic factors, like pheromones, can modulate the expression of genes controlling gregarious colouration, either activating or repressing them. (Simpson, 2005). 

The egg hatches into a nymph, the growth phase. Insects and arthropods have exoskeletons, hard outer shells that do not grow with them. As they increase in size, the exoskeleton must be shed and replaced by a new one; this process is known as ecdysis. The period between ecdyses is called an instar. The locust goes through five instars before reaching adulthood (Fig. 1) (Belles, 2020).  

During the early instars, the body secretes the juvenile hormone, which helps control the maturation of the nymph. Increased hormone levels allow the insect to remain in a juvenile state—growing larger without developing adult features—by influencing the expression of genes associated with nymph characteristics. The juvenile hormone suppresses another hormone, ecdysone, which induces moulting or ecdysis. As the nymph grows, the concentration of juvenile hormone begins to decline and ecdysone is released to trigger the development of adult features like wings and reproductive organs, preparing the locust for adulthood (Singh Kaleka et al., 2019). 

In adulthood, the locust feeds and migrates. While it is normally a solitary critter, adult locusts can travel in swarms if they become gregarious, which is dependent on environmental triggers. During the adult phase, male and female locusts mate; female locusts will then lay eggs, and the cycle will repeat itself (Fig. 1) (Agriculture Victora, 2024).  

The juvenile hormone 

The juvenile hormone is secreted by the corpora allata, an endocrine organ located beneath the aorta. The corpora allata contains many neurosecretory neurons that generate action potentials, but instead of secreting neurotransmitters into a synapse, they secrete hormones into the hemolymph (the bloodstream of the locust). The hormones are secreted as lipid droplets that reach receptors and interact with them (Gilbert, 1973). The basic structure of the juvenile hormone contains a cis oxirane ring (triangular ring containing two carbons and oxygen) and a trans double bond on the sixth carbon (Fig. 2). The natural hormone is not racemic (meaning there is an excess of a single enantiomer within the mixture), containing chiral centres at the tenth (R) and eleventh (S) carbons (Fig. 2). The hormone is synthesized through the terpenoid pathway, which involves the linkages of three five-carbon units called isoprenoids in a long chain  (Nouzova et al., 2018).  

These chemical features and functional groups help the juvenile hormone perform its function within the locust. The terpenoid backbone and the oxirane ring allow interaction with nuclear hormone receptors and proteins that are involved in gene regulation, notably the Methoprene-tolerant (Met). Within the cytoplasm of a cell, the juvenile hormone bonds to the Met protein, which attracts coactivator proteins that help the complex translocate to the nucleus. There, the complex targets the promoter regions of specific genes and binds to them, working as a repressor or an inducer, preventing or facilitating their expression within the locust, respectively. Regulated genes are involved in the maturation of the nymph, but they are also related to its appearance, specifically its colour. The ester functional group before carbon one (Fig. 2) allows for the juvenile hormone’s hydrolyzation. Once the hormone has been secreted and performed its function, it can be broken down using water, which ensures that its effects are finely tuned according to developmental and environmental signs (Applebaum et al., 1997; Nouzova et al., 2018). 

Locust colouration 

Because juvenile hormone influences the transcription of genes affecting locust coloration, it plays a crucial role in the body-color polymorphism of gregarious locusts. Solitary locusts have green and brown colourations, usually earth-coloured, to adapt the individual to the background of its habitat. Gregarious locusts display black and vibrant red colors, along with yellow and orange tones. Their gregarious appearance is a design solution that allows them to ward off predators. Their colouration is a warning signalling that they are part of a large swarming group, making them potentially less palatable and more dangerous. The bright colours are similar to those of inedible toxic organisms, especially those that consume toxic flora. Although some species of locusts consume these plants, others that do not have also evolved the evolutionary strategy of mimicry, allowing them to appear toxic when, in reality, they are not (Sword et al., 2000; Tanaka, 2001). Both the juvenile hormone and another hormone called [His⁷]-corazonin influence locust colour. 

The release of hormones that change the colouration of the locust is dependent on many factors, including population density and environmental factors, like temperature and humidity (Tanaka, 2001). Body-colour polymorphism in locusts is reversible, and insects can switch between solitary and gregarious phases. During the growth phase, locusts with higher levels of juvenile hormone develop a green colour, while those lacking the hormone have a gregarious body colouration. Green nymphs with elevated levels of the juvenile hormone never showed gregarious colouration as adults. Therefore, the juvenile hormone only controls the green pigment, and there must be another factor controlling the dark colours in gregarious locusts. Implantation of the corpora allata of a black locust into a green one increased the amount of black expressed in the originally green locust, which points to a specific dark-colour-inducing compound also originating from the corpora allata (Tanaka, 2001).  

An albino strain of locusts was used to identify the black-inducing factor (Tanaka, 2001). Different treatments were conducted on the compound, which was then implanted into the albino locust that was monitored for colour change. The treatments proved that the factor was a string of heat-stable neuropeptides that were then matched to the identical hormone [His⁷]-corazonin (Fig. 4), which was previously isolated from a species of locust but had no known function. Injections of synthetic [His⁷]-corazonin had the same colour-changing effect. The amount of the hormone injected changed the pigmentation of the locust. More of the hormone led to a darker colour. It was also shown that the timing of the secretion was related to the colouration. Locusts injected with [His⁷]-corazonin at the beginning of an instar turned completely black after ecdysis (Fig. 3); those injected in the middle of an instar developed black patterns with an orange background, and locusts injected towards the end of an instar became brown or purple following ecdysis. None of these locusts entirely resembled gregarious insects in the wild (Fig. 3); therefore, it is hypothesized that both the juvenile hormone and [His⁷]-corazonin control the locust’s solitary and gregarious colourations (Tanaka, 2001).  

[His⁷]-corazonin 

The mechanism of action of [His⁷]-corazonin differs significantly from that of the juvenile hormone, which influences the expression of specific genes. Instead, [His⁷]-corazonin binds to specific receptors in the locust’s epidermal cells, which leads to the upregulation of pigments, especially melanin (Tanaka, 2001). The hormone modulates enzymes involved in its synthesis.  

[His⁷]-corazonin is a relatively short peptide, containing a string of 11 amino acids that help it perform its function (Fig. 4) (Tanaka, 2001). Histidine at the seventh position (Fig. 4) (in its name) allows the peptide to fit into the binding pocket of the corazonin receptor, a G-protein-coupled receptor. G-protein-coupled receptors are membrane proteins that respond to extracellular stimuli and initiate signal cascades (Fig. 5) (Predel & et al., 2007). Upon binding, the hormone activates the receptor by inducing a conformational change, enabling it to interact with G-proteins on the intracellular side, causing them to exchange GDP for GTP (Fig. 5). This activates the G-protein, which is now able to interact with secondary messengers like cyclic AMP or Calcium ions that trigger enzymes through phosphorylation or a change in membrane potential, respectively (Fig. 5).  

The juvenile hormone and [His⁷]-corazonin function in different ways affecting the type of colour regulation. The juvenile hormone works long-term because it regulates gene transcription, the first step in protein synthesis. On the other hand, [His₇]-corazonin activates specific enzymes that act quickly, enabling short-term regulation in response to environmental triggers. This allows locusts to rapidly switch from solitary to gregarious phases following external stimuli. 

Locust behavioral phase change 

Solitary locusts are less prone to locomotion, more sedentary and live in isolation. Gregarious locusts are more active, more social and, thus, live in swarms (Pflüger & Bräunig, 2021). There are two sensory pathways that trigger the phase change of locusts from solitary phase to gregarious phase. First, there is the thoracic pathway stimulated by mechanosensory when locusts get in contact with each other. Second, there is the cephalic pathway driven by the olfactory and visual stimuli (Anstey et al., 2009). Thus, sight, smell and touch are the main stimuli to locust phase change. Furthermore, not all locust species have been analyzed in dept. The most studied locust species are the migratory locust, Locusta migratoria, and the desert locust, Schistocerca gregaria (Pflüger & Bräunig, 2021). A time-related variation in phase changes is distinguished between these two species. The migratory locust has slower gregarization and faster solitarization, whereas the desert locust crowds more rapidly and has slower solitarization (Guo et al., 2013).  

Dopamine  

Dopamine is a neurotransmitter that controls movement, pleasure, motivation, arousal and memory in organisms. Through gene observation and analysis, it was determined that the catecholamine metabolic pathway was the most affected one in the fourth stadium of gregarious development for migratory locusts (Ma et al., 2011). Two gene expressions were analyzed extensively: the pale gene and the vat1 gene. The pale gene encodes the enzyme tyrosine hydroxylase which is the rate-limiting enzyme for the synthesis of dopamine. The vat1 gene encodes a protein responsible for the synaptic release of dopamine (Fig. 6). The development of locust was divided into five stadiums and genes were detected through quantitative PCR analysis of locust head tissues. During the five stadiums of development for a gregarious locust, the pale gene had a high expression in the first stadium and a weakening of the gene expression was observed by the end of the development stages. For the vat1 gene, low expression was observed in the first stadium and there was an increase of expression by the fifth stadium. The time-related gene expressions demonstrate an early stage of dopamine synthesis and a late stage of dopamine release (Ma et al., 2011). With an increase in crowding, an increase in gene expressions can be seen. In solitary locust, both genes were less expressed. The reduction in dopamine synthesis and release explains the reserved and less active behavior of the solitary locust (Ma et al., 2011) 

Fig. 6 Schematic representation of dopamine metabolic pathway. [Adapted from Ma et al., 2011] 

Experiments using contrast microscopy showed higher dopamine levels in the metathoracic ganglia of isolated desert locusts compared to long-term crowded ones. Dopamine was injected into different test subjects which were then subjected to crowding. Two control groups injected with saline were set: gregarious locusts and solitary locusts. 60% of the gregarious control group reacted to stimuli and 38% of the solitary control group reacted. 32% of the gregarious locusts injected with dopamine reacted to the stimuli and 20% of the injected solitary locusts reacted (Alessi et al., 2014). Thus, it is observed that dopamine injections decrease the number of locusts reacting to the stimuli. This makes dopamine a key neurotransmitter responsible for the induction of behavioral change from gregarious to solitary. Dopamine reduced efficacy of synaptic inputs to the thoracic neurons controlling insect flight and locomotion, thus explaining the less active behavior of solitary locusts (Alessi et al., 2014). This decrease in activity helps locusts maintain a lifestyle of high endurance and optimize their food-intake in harsh environments. 

Serotonin 

Although dopamine plays a significant role in locusts behavioral phase transition, the shift of phase is incomplete without the involvement of other chemicals, such as serotonin. Serotonin is a neurotransmitter that controls mood, appetite, sleep and reproduction.  

Amid crowding, the solitary desert locust can turn to the gregarious phase in less than two hours. With the identification of the sensory stimuli triggering behavioral change, the central nervous system is divided between the brain, subject to olfactory and visual stimuli, and the thoracic ganglia, subject to the mechanosensory stimulus. The brain controls the thoracic ganglia which regulates locomotion (Guo et al., 2013). During the behavioral change of a solitary desert locust, there is an increase in serotonin levels in the thoracic ganglia of the central nervous system. A positive correlation between serotonin levels and gregarization of the desert locust was determined through different manipulations. A binary logistic regression model with probabilistic metric was set with P_greg of 0 representing the solitary phase and P_greg of 1 representing the gregarious phase (Anstey et al., 2009). First, serotonin receptor antagonists were injected into the solitary locust to block the action of serotonin. The locust failed to change phase with a P_greg of 0.27 for the thoracic pathway and 0.07 for the cephalic pathway (Fig. 7). Second, serotonin precursor was injected into solitary locusts, and they were observed for thirty minutes. The control solitary locust was subject to crowding and showed some behavioral change after thirty minutes. The injected locust who remained isolated had a similar result from the control. The injected locust put into a crowded environment went through significant gregarization. Thus, serotonin accelerates behavioral gregarization when in contact with sensory stimuli (Anstey et al., 2009).  

Fig. 7 Behavior of locusts injected with serotonin receptor antagonists that block the action of serotonin and then exposed to sensory stimuli that normally induce gregarization (left column) is shown. Saline-injected controls are shown in the right column. Locusts injected with serotonin-receptor antagonists ketanserin and methiothepin (1 mM) and given either 1 hour of femoral mechanosensory stimulation or 1 hour of olfactory and visual stimulation from other locusts. [Adapted from Anstey et al., 2009] 

In contrast, the opposite correlation was found in migratory locusts. The serotonin neurotransmitter enhanced the behavioral change of gregarious locusts to solitary locusts. The injection of serotonin in an isolated gregarious locust accelerated its change to a solitary locust. Since the brain controls and instructs thoracic ganglia, researchers decided to measure serotonin levels in the brain. The results of the experiment are an increase in serotonin during isolation of gregarious locusts and no change in serotonin levels during crowding of solitary locusts (Guo et al., 2013). From previous reviews, the increase in serotonin decreases sensory reactivity and protects against overstimulation. Thus, this would explain the slower locomotion and isolation of solitary locusts. Serotonin would reduce responses and activities of the locust to exterior factors. Furthermore, an increase in serotonin 5-HT₂ receptor expression during crowding was revealed. The low expression of the receptor partially induces gregarious behavior, but a rapid increase in expression activates serotonin signaling pathways and inhibits the phase change of the solitary locust (Guo et al., 2013).  

The contradictory role of serotonin and dopamine in locusts can be explained by several factors. The locusts analyzed in these separate studies are of different species, thus resulting in a species-specific behavioral pattern. The research conducted with desert locusts measured serotonin levels from the thoracic ganglia whereas the research conducted with migratory locusts measured them from the brain. The duration of the experiment differed where one was a short-term application of serotonin and the other a long-term and systemic application. Each experiment used different methods and manipulations ranging from direct injection of the neurotransmitter to gene analysis (Guo et al., 2013). 

Gene expression 

The phase change of locusts is due to polyphenism, the occurrence of different phenotypes in a population influenced by their environments and not their genes. In the specific case of the locust, population density is the factor influencing the phenotype of the locust. Gene expression levels of 532 genes vary depending on the solitary and gregarious phase of the locust (Guo et al., 2011). From bioinformatics analysis, several chemosensory proteins genes and the takeout gene LmigTO1 were expressed at a much higher level in the gregarious phase than the solitary phase. These genes are related to the transition of attraction or repulsion behavior of the locust towards other individuals. Through RNA interference, the removal of a chemosensory protein gene in a gregarious locust made it transition to a solitary phase and the removal of the takeout gene in a solitary locust led it to its gregarious phase (Guo et al., 2011). Thus, the expression levels of chemosensory proteins gene and the takeout gene correlate to the level of attraction or repulsion of a locust. Gregarious locusts have a higher gene expression for chemosensory proteins which leads to the behavioral change of attraction. Solitary locusts have a higher gene expression of the takeout gene for a repulsive behavioral change. Since these genes do not affect the locomotor activity of locusts, chemosensory proteins and takeout genes only initiate the transition process. 

Chemical Communication 

Locusts, including the desert locust Schistocerca gregaria, use chemical communication extensively in modulating numerous behavioral events, including but not limited to courtship, reproduction, and aggregation. These behaviors follow from the interaction of pheromones, cuticular hydrocarbons, hormones, and volatile compounds that allow both individual interactions and group dynamics to take place. Chemical signals are involved in all of these, from mate attraction up to the coordination of large swarms. These chemical processes give a better understanding of how locusts reproduce and aggregate, and the biochemical underpinning of their complex behavioral ecology. 

Pheromones and Mate Attraction 

Generally, in locusts, pheromones are considered the seminal chemical signals controlling sexual reproduction. In the case of the locusts, females emit sex pheromones to attract males; this in turn allows mate recognition in very high-density aggregations, such as the swarms of S. gregaria. In general, these are long-chain aldehydes, alcohols, and esters, synthesized from the fatty acids through a series of biochemical reactions involving oxidation, reduction, and elongation (Coombes et al., 2018). The pheromones are usually emitted by special glands near the abdomen, which diffuse into the air and are recognized by males on antennal chemoreceptors (Fig. 8). 

Fig. 8 Subsections of the male antennal chemoreceptors, and the pathways that take them to the receiving area of their brain (Stern et al. 2012). 

Once these pheromones are detected by a male locust, he is lured towards the female and starts with  displaying several courtship postures like the vibrating of wings, the movement of antennae, and the copulatory postures. Because of this type of chemical signaling, males can target future mates among the tumult of big aggregations. Juvenile hormones, therefore, initiate the production of sex pheromones whereby such chemicals are synthesized and released during the female’s fertile period (Ferenz et al., 2003). Accordingly, females timed their mating availability to correspond with the release of sex pheromones so that copulation occurs at the best reproductive time. 

Cuticular Hydrocarbons and Sexual Recognition 

Apart from sex pheromones, cuticular hydrocarbons or CHCs also play a significant role in sexual recognition and mate choice. These are derived from the locust cuticle and not only act as species-specific markers but also provide information on reproductive status. For example, in the females of S. gregaria, CHC profiles change during their reproductive cycle and give information on their sexual receptivity to males. These hydrocarbons are produced by fatty acid elongation and can undergo modifications, like methylation or saturation, that affect their volatility and hence their detectability (Hassanali et al., 2005). 

The males of S. gregaria detect receptive status via a CHC profile, thereby avoiding courtship that would be inappropriate. Non-receptive females usually have normal CHC patterns which signal their status and inhibit the useless efforts of the males. The chemical signaling prevents wasting mating effort on females in non-receptive physiological status, increasing reproductive efficiency, and preventing unwanted copulation (Coombes et al., 2018). 

Courtship Inhibition and Sexual Conflict 

Locusts also employ chemical signals in courtship inhibition, wherein females regulate mating opportunities. Female locusts release pheromones for courtship inhibition if they are not in the receptive state or want to avoid mating with lower-fitness males. Such pheromones inhibit sexual behavior in males and prevent any undesired mating attempts (Seidelmann et al., 2002). Understanding the mechanism of courtship inhibition is important in managing sexual conflict, where the male, under the strong drive to mate, can pursue courtship even when the female is unreceptive. Females avoid harassment through the release of inhibitory pheromones and thus ensure that copulation occurs only when it is most advantageous to their interest. This subtle modulation in courtship enables females to maintain control over their reproductive decisions and results in optimized mate selection. 

Hormonal Control of Pheromone Production 

Sex pheromones and courtship-inhibiting pheromones are released in response to a change in hormonal state, notably juvenile hormones and ecdysteroids. Juvenile hormone-which governs reproductive maturity-triggers the biosynthesis of sex pheromones during the fertile phase of the female reproductive cycle (Ferenz et al., 2003) (Fig. 9). As shall be discussed below, this same hormone increases the receptivity of females so that mating can occur precisely during this period. In addition, ecdysteroids-that regulate molting-regulate the time course of reproductive behavior and influence the release of both sex pheromones and courtship-inhibiting pheromones. High ecdysteroid levels correlate the female’s behavior with her reproductive physiology and form a tight mechanism for the control of mating. 

Fig. 9 Juvenile Hormone and its resulting effects in the brain and receptors of the reproductive system. 

Locust Aggregation 

Besides courtship and reproduction, locusts also show a strong aggregation behavior, particularly in the gregarious phase when they take the form of huge swarms. Aggregation plays an important role in locust survival and reproductive strategies, wherein chemical signaling is at the center. Locusts aggregate because of environmental cues and the chemical signals, especially aggregation pheromones, from individuals themselves that attract other individuals. These chemical signals ensure that the movements and activities of locusts are coordinated with one another; large swarms are therefore easily formed, and this in turn assists the transition from solitary to gregarious behavior. 

The volatile compounds initiating an aggregation response are produced both by immature and mature locusts. The chemicals are typically cuticular hydrocarbon derivatives, which are then detected by conspecifics via specialized antennal chemoreceptors. For instance, in S. gregaria, aggregation pheromones trigger increased locomotion and attraction, thereby making individuals aggregate. Aggregation is related closely with density-dependent effects-increasingly, as locusts are more in number, aggregation pheromones are produced more intensively, enhancing attraction among individuals and therefore encouraging swarm development  (Seidelmann et al., 2002). 

It also mediates behavioral synchrony in these groups, which maintains the locusts in proximity to one another and travel together. Swarm capability forms the very foundation of successful migration whereby locusts can cover long distances in search of food and suitable breeding grounds. The aggregation pheromones may also allow for reproductive synchronization among conspecifics, since individuals of a similar age and reproductive condition come together, thereby providing the opportunity to maximize mating. 

Chemical Factors in Oviposition and Aggregation of Females 

Chemical signaling at oviposition also plays a vital role in the aggregation of locusts, especially females. Ovipositing females in S. gregaria release specific pheromones attractive to other females to the site of oviposition. Such oviposition-related pheromones serve as recruitment signals, guiding other females to suitable egg-laying sites (Norris et al., 1970). Aggregation of females onto these sites depends on two factors: locust density and chemical signals prevailing in the environment. 

In one study, it was demonstrated that during the gregarization phase of locusts, females that oviposit release a pheromone which elicits a positive aggregative response among conspecific females (Ferenz et al., 2003). The effect of such pheromones is that of synchronizing egg-laying activities, aggregating females in large numbers at an oviposition site. This is advantageous because, with such high density, eggs hatch more easily. Such aggregation allows for efficient use of space and resources, maximizing reproductive output in swarming locust populations. 

Cannibalism and Chemical Signalling 

Cannibalism is one of the interesting aspects of locust behavior, which is involved at the level of chemical signaling, particularly under conditions of crowding. Locusts have been recorded under specific conditions to exhibit cannibalistic behavior caused either by stress or scarcity of resources. Chemical signals on alarm pheromones provide information about potential danger or carcasses and, therefore, serve as stimuli for cannibalistic behavior. Their chemical nature is still under investigation, but it is considered that volatile compounds from injured or dead locusts are implicated in the induction of this behavior (Couzin et al., 2023). 

Although it does not relate directly to either mating or aggregation, locust cannibalism is a response to extreme environmental stress and may be influenced by the same chemical pathways as other social behaviors such as aggregation and courtship. We gain from this an understanding of how such chemical signals can trigger such behaviors and widen our view on the locust’s chemical ecology to include complex social dynamics and survival strategies. 

Conclusion

Locusts must survive in environments with fluctuating resources, population stresses, and predation pressure. Through their complex chemical adaptations, locusts have evolved to adjust behavior, development, and social interactions to survive and thrive. Locusts must develop and adapt to environmental cues with precise timing. Through the use of the juvenile hormone and [His₇]-corazonin, locusts’ development, molting and pigmentation are regulated in responses to environmental conditions. With controlled life cycle stages and physical traits, the locust has smooth transitions through developmental stages and appropriate features for survival.  

The resources and environment around locusts are everchanging and require constant adjusting behavior and activity to cope with possible challenges. Dopamine and serotonin are neurotransmitters that adjust the behavior, movement and social interactions of locusts. These transmitters are the driving force behind the locust responding to its surroundings, seeking resources, and adapting its social behavior, all to help balance energy conservation with necessary increased activity.  

Locusts must navigate social dynamics and coordination to survive and reproduce. Pheromones – chemical signals communications – facilitate foraging, predator avoidance, and swarm formation through both solitary and gregarious phases. These evolutionary adaptations provide effective, adaptive solutions to potential environmental challenges. 

Understanding the interconnected chemical system in locusts offers valuable insights for comprehending and potentially managing their impacts on ecosystems and agriculture. 

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