Social Wasps: A Chemical Analysis 

Andrew Habelrih, Eliot Azar, Malak Zakaria

Abstract

This paper discusses the different chemical and biological aspects surrounding wasps which have evolved to fit each species behavior. The venoms of social and solitary wasps contain key components such as phospholipases, mastoparan, hyaluronidase, kenins, antigen 5, and neurotoxins. Each of these compounds amplifies the overall effect of the venom on tissue, maximizing its potency by causing pain, swelling, allergic reactions, and paralysis. The concentration of each component varies from solitary to social wasps depending on behavioral needs. Pheromones are also a major component for wasps. Their uses vary from communication, inducing reproduction, colony defense, and trail making. Female wasps emit sex pheromones to attract males, alarm pheromones trigger a defensive response in the colony, and trail pheromones create a guiding trail to resources or new nesting sites. Cuticular hydrocarbon chains are also explored in this paper by their waterproofing and communication properties thanks to their long carbon chains. Furthermore, the nest-building practices of wasps are discussed by their use of saliva and plant fibers to construct strong shelters which have the properties to regulate temperature.  

Introduction

Despite their small size, insects are remarkable creatures with fascinating abilities across many aspects of their lives—defense, reproduction, and communication are just the beginning. One insect that has particularly caught the eye of the scientific community is the social wasp. Having evolved in unique ecological environments, they exhibit specialized behavior in their interactions with their environment, including interactions with other wasps from their colony, other animals, or flora. Indeed, social wasps live in colonies and require hundreds of other individuals to ensure the survival of themselves as well as that of the colony. On the other hand, solitary wasps also interact with their environment in particular ways to be able to survive. The specific constitution of wasps’ venom, varying between social and solitary wasps, grants them the ability to respond to threats in an efficient and intricate way. Each substance present in the venom serves a specific defensive or offensive purpose and has different effects in the organism of the victim, ranging from allergic reactions to attacks on the nervous system. Furthermore, wasps have intricate mediums of communication with each other, and every different purpose of communication follows a similar mechanism while involving different substances. Communication is mainly mediated by pheromones, a chemical substance released by wasps allowing them to transmit messages to other individuals. Sex pheromones play an immense role in reproduction, while alarm pheromones allow wasp colonies to unite against a threat and trail pheromones guide wasps to different destinations. Information can also be communicated with cuticular hydrocarbons on a wasp’s cuticle, helping wasps recognize members of their colony. Colonies build developed nests with multiple adaptive structural features, helping wasps to thrive in their environment. The study of the chemical aspects of these various phenomena allows us to shed light on the elaborate mechanisms which govern the complicated organisms that are wasps, showcasing the power of millions of years of evolution. 

Key components in the venom of wasps 

The venom of social wasps is composed of various bioactive components such as enzymes, peptides, and proteins. Phospholipase A1 (PLA1) and phospholipase A2 (PLA2), are both enzymes that break specific bonds in phospholipids by hydrolyzing them. PLA1 breaks the sn-1 position of glycerol and PLA2 focuses on cleaving the sn-2 position as shown in Figure 1 (Yoon et al., 2020).  

Fig. 1 Phospholipase A1 and A2 attacking the sn-1 carbon and the sn-2 carbon in the phospholipid bilayer (Perez-Riverol et al., 2019) 

The importance of phospholipids in biological systems is critical since cellular membranes are composed almost entirely of these molecules. As such, this causes cellular lysis and the destruction of tissue in the area in which the venom is injected by the destruction of cells. PLA2 also converts phospholipids into arachidonic acid, a precursor to inflammatory molecules called eicosanoids, which include prostaglandins, thromboxanes, and leukotrienes (Rádis-Baptista & Konno, 2020). 

Another component in wasp venom is a peptide called mastoparan. It is composed of 14 amino acids, and it is found in an α-helical structure as shown in Figure 2 (Alhakamy et al., 2021). The primary effect that this peptide has is its interaction with mast cells. Mast cells are leukocytes (white blood cells) in animals that play a role in allergic reactions, inflammation, and defense against pathogens. They contain large granules that encase many biomolecules such as histamines, proteases, and cytokines, which lead to inflammation in a tissue. Mastoparan induces the release of the content within the granules causing swelling, redness and itching (Ye et al., 2023). Another characteristic of this compound is its amphipathic nature, meaning it has both polar and non-polar properties that facilitate interactions with cell membranes. This allows the peptide to lodge itself in the phospholipid bilayer of a cell membrane to create a pore as seen in Figure 2. Through this pore, the contents of the cell start leaking out, leading to the death of the cell. However, this process occurs more often with bacteria cells which leads current research in using mastoparan as an antimicrobial substance (Zhao et al., 2023).  

Fig. 2 Interaction of amphipathic peptides such as mastoparan with the cellular membrane to lead to the formation of pores. (1) Amphipathic peptides are both hydrophobic (red) and hydrophilic (blue) which allow them to interact with the phospholipid bilayer. (2) They can position themselves in the phospholipid bilayer by positioning their hydrophilic residues toward the aqueous environment and their hydrophobic residues toward the lipid core causing an expansion of the outer layer. (3) As the concentration of these peptides increases in a given area, the overall stress increases causing instability. (4) To reduce the stress of the phospholipid bilayer, the peptides orient themselves perpendicularly to the bilayer causing the formation of pores. (Kuwana, 2018) 

In addition to the previous compounds, hyaluronidase is an enzyme also found in many venoms including wasp venom. This enzyme targets the hyaluronic acid found in the body. Hyaluronic acid is a polysaccharide (an addition of many sugar molecules) which has great water holding capabilities to aid tissues to stay lubricated and hydrated (Rádis-Baptista & Konno, 2020). This compound plays a major role in the structural integrity of tissues. As such, when hyaluronidase breaks down hyaluronic acid, it creates a more fluid environment in the tissue which eases the spread of other components of the venom in the surrounding area and sometimes into the blood stream as shown in Figure 3. This enhances the total efficiency of the venom since the different compounds can reach a higher number of cells and cause more damage to the tissue (Rádis-Baptista & Konno, 2020).  

Fig. 3 Hyaluronidase catalyzing the decomposition of hyaluronic acid (hyaluronan) in tissues (Buhren et al., 2016) 

Antigen 5, as shown in Figure 4, is one of the most potent allergens found in the venom of wasps. It belongs to a family of proteins called the CAP superfamily (cysteine-rich secretory proteins, antigen 5, and pathogenesis-related proteins). This family plays an important role in immune responses and inflammation (Blank et al., 2020). Antigen 5 is rich in disulfide bonds which help it maintain a folded shape and protect it from external factors which may degrade it. It is one of the primary proteins that cause allergic reactions in more sensitive animals because when it is present in a body, the body mistakes antigen 5 as a harmful substance. The release of antibodies¹ and histamine begins which can lead to dire symptoms such as anaphylaxis (Blank et al., 2020). Compounds such as phospholipase A2 and hyaluronidase are commonly found in the venom produced by bees but antigen 5 is unique to wasps. This means that animals allergic to wasps may not necessarily be allergic to bees (Yoon et al., 2020).  

Fig. 4 Molecular model of the antigen 5 allergen from social wasp venom in three dimensions (Bazon et al., 2018). 

Kinins are small peptides which play a major role in the inflammatory response of the body. They are part of a system which regulates blood pressure, inflammation, and pain. These molecules are generally released by a tissue when injured to stimulate the relaxation of blood vessels. Kinins also directly activate pain receptors in the area. Bradykinin and kallidin, two molecules belonging to the kinin group are found in wasp venom. As such, after being stung from a wasp, the pain distracts the victim long enough for the wasp to escape or to disable the prey (Griesbacher et al., 1998).  

Neurotoxins in wasp venom are peptides that target the nervous system. These toxins interfere with the ion channels in nerve membranes by blocking or alternating the flow of sodium and potassium ions which allow nervous transmission (Schmidt, 2019). A nervous impulse functions by creating a difference of charges on the inside and the outside of the nervous membrane by changing the concentration of these ions. As such, this disruption can paralyze, have a numbing effect or heighten the pain felt in the tissue affected by the sting. Neurotoxins are particularly useful for wasps in subduing prey, since they immobilize smaller insects quickly. In larger animals, these neurotoxins contribute to a sharp and intense pain due to the difference in complexity between the nervous systems. Although neurotoxins are more commonly associated with predatory species of wasps, they also play a defensive role by giving social wasps an advantage in deterring larger predators from their nest by causing rapid, painful reactions (Schmidt, 2019).  

Differences between social and solitary wasps  

Social wasps and solitary wasps differ in venom composition since they have different uses for their venom. Social wasps use their venom for defense by targeting threats to the colony. This increases the potency of their venom components—PLA1, PLA2, mastoparans, and kinins—causing inflammation and allergic reactions that help kill predators or deter threats (Yoon et al., 2020). The quantity of messenger RNA being made per gene to produce PLA2 exceeds 600 transcripts per million (TPM)² and can reach 106395 TPM for PLA1 in some species. Solitary wasps use their venom for hunting purposes and as such, the venom may contain higher quantities of neurotoxins. Their goal is to paralyze their prey to feed on it or to feed it to their larvae. The activity of the PLA1 gene in solitary wasps is around 1322 TPM and achieves a maximum of around 952 TPM for PLA2. PLA2 aids the paralysis of the tissue by destroying key cells linked to the nervous system. Higher transcripts per million for genes linked to the production of neurotoxins are also found in solitary wasps at values around 7387 TPM compared to 1000 TPM for many social wasps. This is a direct result of evolution linked to the behavior of social and solitary wasps (Yoon et al., 2020).  

These different compounds in the venom also account for the pain felt after a sting. Social wasps sting an intruder to deter the threat from the nest. As such, their stings are more painful than stings from solitary wasps which have the objective of paralyzing prey (Schmidt, 2019). This also aligns itself with the values of transcripts per million measured in the genes of these different wasp species. The higher quantities of PLA1 and PLA2, mastoparans, and kinins account for the higher pain caused by the sting and the venom. The quantity of pain occurred by the sting is measured on the Schmidt Sting Pain Index (SSPI) which rates the pain of different insect stings on a scale of 1 to 4. The sting of different social wasps can vary between a pain level of 2 for yellowjackets and 3 for hornets. The average pain level for solitary wasps is around 1 (Schmidt, 2019). Tarantula hawks are an exception to this trend because this solitary wasp has the second most painful sting of all insects due to the neurotoxins found within its venom. These neurotoxins have evolved to have enough strength to paralyze tarantulas. Tarantula hawks, usually around 11 cm in length, also inject a large quantity of venom compared to other wasp species to ensure that their prey, which can often be much larger than them, is fully immobilized. As such, the quantity of the neurotoxins injected in the tissue is much larger than an average solitary wasp (Schmidt, 2019).  

Fig. 5 Examples of the sting of different insects on the Schmidt Sting Pain Index (SSPI) (Brenna Shea, n.d.) 

Biological applications for wasps and wasp venom 

The venom of wasps is what allows it to be a highly effective natural pest controller. The presence of wasps helps in the regulation of biodiversity to limit the growth of certain populations of insects (Rádis-Baptista & Konno, 2020). An example of this are paper wasps that hunt caterpillars. As such, specific wasps are often used by farmers to target certain species of crop-damaging insects such as aphids and whiteflies. This practice encourages a more ecofriendly approach by lowering the use of chemical pesticides which are harmful to the environment by harming non-target species, polluting water supplies, and can lead species of insects to build an immunity against such pesticides (Rádis-Baptista & Konno, 2020). In certain regions affected by climate change, new invasive pests might appear threatening crops. Wasps are also an effective counter measure in these cases since they can biologically adapt their feeding patterns instead of having to use different pesticide solutions (Rádis-Baptista & Konno, 2020). 

Pheromones 

As most wasp species live in colonies, communication within this colony is essential to its survival. Indeed, communication is crucial to processes such as reproduction, defense, or movement. Thus, the communication medium must be effective, reliable, and long-range. Visual signals allow to transmit information efficiently, but they imply a major downside, which is that wasps must be in each other’s field of view in order to communicate. Furthermore, acoustic signals are also an effective mode of communication, and while they have a longer range than visual signals, they can still be inhibited by many environmental factors and the range of efficiency is limited (Bruschini, 2010). This is why wasps have evolved to employ chemical signals to communicate, as these substances can travel long distances while staying intact and can be perceived efficiently by other wasps (Bruschini, 2010). These substances are called pheromones and are used by insects and other animals to communicate for many different purposes. 

A pheromone is defined as a chemical substance released by an organism which causes a specific reaction in other individuals. These reactions can be physiological or behavioural, and they are specie-specific, meaning that individuals are not sensitive to pheromones released by other species, thus avoiding undesirable phenomena such as inter-species mating. Pheromones are mainly composed of hydrocarbons and fatty acids (Bruschini, 2010). They are generally synthetized de novo, meaning that they are synthetized inside the insect’s organism, as opposed to being derived from dietary intake (Blum, 1972). Pheromones are mainly secreted by glands located close to the reproductive organs of the wasp, such as Dufour’s glands, abdominal glands or mandibular glands, depending on the type of pheromone being secreted (Blum, 1972). 

Fig. 6 Schematic locations of exocrine glands of wasps (Bruschini, 2010) 

Pheromones being a very volatile substance, they are then released and diffused through the air for other wasps to detect (Bruschini, 2010). Other individuals can then perceive these pheromones and undergo behavioural and physiological changes in response, depending on the type of pheromone in question. 

Sex pheromones 

The most abundantly produced pheromone is the sex pheromone. Indeed, it is used by many species to favour mating and reproduction. There are two types of sex pheromones in wasps: the first one being secreted by females and the second one by males. While they are both classified as sex pheromones, they serve very different purposes (Bruschini, 2010). 

Female sex pheromones, used to attract males as mating companions and stimulate their copulatory behaviour, are mainly produced in the Dufour’s gland as well as tergal and sternal abdominal glands on the wasp’s abdomen, near its reproductive organ (Bruschini, 2010). Secretion of these pheromones is synchronized with the female’s reproductive cycle, thus facilitating fertilization during mating (Bruschini, 2010). When released, sex pheromones, a very volatile substance, are diffused to long distances in order to attract males. However, these female sex pheromones are not always species-specific. Indeed, some species’ females produce pheromones which can attract males from different species (Bruschini, 2010). To avoid cross-species mating, females also secrete contact pheromones. These pheromones, as opposed to the sex pheromones described above, are species-specific, and are functional by contact or very close range. They are carried by both males and females and allow males to recognize females from their own species (Bruschini, 2010). 

Wasps use a complex mechanism to detect sex pheromones and indulge in mating behavior. This process is mainly mediated by their antennae, more specifically in the antennal sensillum, a hair-like structure in which the dendritic processes of the sensory neurons occur (Breer, 1979). It contains the dendrites of sensory neurons, and is filled with a fluid, the sensillum lymph, which protects the neuron (Breer, 1979).  The membrane of the sensillum is covered in pores, allowing pheromone molecules to enter. Pheromones then bind to pheromone-binding proteins, which transport the pheromone through the fluid to the dendrite. The dendrite then responds to the presence of pheromones with a change in the membrane potential, called the receptor potential, which then converts into an action potential to the brain, which encodes temporal, spatial and intensity information about the pheromone stimulus (Breer, 1979). Male wasps employ an interesting design solution and compare the information obtained by different receptors, located on each antenna, and follow the gradient of concentration of pheromones perceived by each receptor, thus making their way to the female wasp (Breer, 1979). However, this process entails an inconvenience related to the precision of such measurements of the pheromone stimuli. Indeed, the receptors must be very sensible to perceive the smallest differences of pheromone concentration, up to the molecular level. In order to maintain a good temporal resolution of measurements, pheromone molecules must be deactivated rapidly once they are perceived by the dendrite. Indeed, enzymatic activity in the sensillum lymph inactivates pheromone molecules to optimize the precision of measurements (Breer, 1979). Experimental results show that up to a million molecules can be inactivated in half a second, which corresponds to the time required for a male wasp to change its flight pattern in response to pheromonal stimuli (Breer, 1979). 

Male wasps also produce sex pheromones, but they serve a different purpose. While male sex pheromones are not as well-known as female sex pheromones, many experiments show that they are released by abdominal and leg glands. Their purpose is mainly to mark their territory and reduce mating competition among other males (Bruschini, 2010). 

While the chemical composition of sex pheromones varies across species, they are generally constituted of a long unsaturated hydrocarbon chain and contain groups such as esters, alcohols and aldehydes. For instance, hexadecyl acetate and hexadecanal have been identified as key components of sex pheromones for certain species of wasps (Murray, 1972). 

Fig. 7 Pseudocopulation of the male scoliid wasp on the mirror orchid (Eaton, 2021) 

Sex pheromones can sometimes be used to trick the male wasp. The mirror orchid is a flower in Mediterranean Europe and Northern Africa, and it has an incredible resemblance to the female of the scoliid wasp. Indeed, it releases pheromones similar to the female wasp’s, thus attracting the male scoliid wasp. Furthermore, the flower bears a shiny blue color mimicking the blue wings of the female scoliid wasp. Lastly, the male wasp perceives tactile stimuli from the flower which resembles the female’s texture. All these factors push the male wasp to attempt mating, but they end up pollinating the flower. This is a design solution from the orchid plant to engage the male wasp in order to get pollinated.  This is called pseudocopulation (Eaton, 2021). 

Alarm pheromones 

Beyond reproduction, other types of pheromones also serve important purposes especially in social wasp populations, such as the defense of the colony. Indeed, alarm pheromones, the second most abundantly secreted pheromones, are essential to ensure colonial defense against various external threats (Bruschini, 2010). Alarm pheromones are generally constituted of molecules with lower molar mass to increase their volatility. A very common example of an alarm pheromone is isopentyl acetate, which can be found in many wasp species (Murray, 1972). 

In the presence of a danger, such as a predator, social wasps will release alarm pheromones from their venom gland in order to warn other individuals in the colony (Bruschini, 2010). Upon detecting this pheromone, wasps will adopt a more aggressive defensive behavior towards the source of danger to neutralize it. For instance, wasps will repetitively sting a predator in response to detection of conspecifics’ alarm pheromones (Jeanne, 1981). This common signal for the entire colony also allows rapid synchronized action against the threat, thus maximizing protection of the colony. Indeed, experimental studies show that an entire colony of wasps can be alerted of a threat in the span of 1.5 seconds, an efficient time allowing immediate response (Bruschini, 2010). 

The general reception of alarm pheromones is similar to that of sex pheromones. However, the behavioral response process is slightly different, as it also relies on other stimuli. Once on the site of the threat, wasps synchronize their responses with visual cues. While neither the chemical stimulus nor the visual cue is enough to stimulate an appropriate response to the threat, both are combined to maximize the efficiency of the response (Bruschini, 2010). This shows how wasps have evolved as a superorganism to ensure not only individual survival, but also colony subsistence. 

Trail pheromones 

Another type of pheromone which is widely used in insect populations is trail pheromones. While it is more common in ground insects such as ants, which can leave chemical trails on the ground as opposed to flying insects, it has also been shown that social wasp populations widely use trail pheromones (Czaczkes, 2015). Trail pheromones are released by wasps on substrate in order to guide other individuals to a specific destination. These other wasps will detect trail pheromones with their antennae, similarly to the process discussed above, following the concentration gradient of pheromones (Breer, 1979). This process works as a positive feedback loop. Indeed, it has been shown that the number of wasps following a trail is proportional to the quantity of trail pheromone. Thus, when a wasp creates a trail by releasing trail pheromones, other wasps follow this path. These wasps will also release pheromones, thus intensifying the pheromone trail and attracting more wasps. This property of trail pheromones is very useful and allows wasp colonies to efficiently exploit a certain resource or move to another location (Czaczkes, 2015). 

Trail pheromones have various uses among wasp colonies. For instance, they are released by a wasp in order to guide his colony to a new food source. Wasps can also guide their colony to a new nest site by using trail pheromones (Clarke, 1999). To do so, however, two types of trail pheromones are required: long-lasting pheromones and short-lived pheromones (Czaczkes, 2015). Short-lived pheromones are used as described previously: a wasp releases short-lived trail pheromones to guide other wasps to a certain destination, such as a food source, to exploit it. Since these pheromones are short-lived, they will be neutralized when the food source is completely exploited (Czaczkes, 2015). Long-lasting trail pheromones serve another purpose. As they last longer, they are used to mark territories and exploration paths, and they serve as long-term guides for more frequently used routes. For instance, they could link old nest sites to the current nest of the colony (Czaczkes, 2015). As trail pheromones generally last longer than sex pheromones or alarm pheromones, they are composed of more stable, less volatile molecules, such as long-chain hydrocarbons with alcohol and ester groups. The chemical formula of pheromones varies strongly amongst different species, but trail pheromones generally have a bigger molar mass. (Tillman, 1999). 

Ultimately, pheromones are chemical signals allowing wasps to communicate effectively in a myriad of different contexts. The huge chemical diversity of pheromones allows wasps to thrive as individuals and as superorganisms. 

Cuticular Hydrocarbon Chains 

The cuticle of social insects is crucial to the survival of any insect species. It protects them against desiccation by having waterproofing properties and acts as a means of communication between individuals of that species. The waxy cuticle is composed of long hydrocarbon chains, mainly saturated linear alkanes and unsaturated branched alkanes and alkenes, which each have different functions. Linear alkanes are responsible for waterproofing due to their high melting point, while branched alkanes and alkenes with a lower melting point are responsible for chemical signaling between individuals. Some compounds in the cuticle such as methyl-branched alkanes and linear alkenes have an intermediate melting point and can affect both cuticle functions. The correlation between the melting temperatures of these compounds and their function is shown in Figure 8. The synthesis of the cuticular hydrocarbon chains (CHCs) happens in the insect’s oenocyte cells and needs products from the fatty acid synthesis to start its reactions. Two different fatty acid synthases (FAS) are involved in the synthesis of CHCs: cytosolic FAS for saturated alkanes and alkenes, and microsomal FAS for unsaturated methyl-branched CHCs. As seen in Figure 9, after FAS synthesizes the fatty-acyl CoA chain, elongases elongate the carbon chain while desaturases add double-bonds to it. Then, reductases convert the acyl-CoA side chain to an aldehyde and finally, an enzyme called cytochrome P450 converts the molecule to hydrocarbon chains in a decarbonylation reaction. (Chung et al., 2015) 

Fig. 8 Function of CHCs as a result of their melting temperatures (Chung et al., 2015) 

Fig. 9 Cuticular Hydrocarbon Chain synthesis (Chung et al., 2015) 

In wasps, CHCs vary depending on the species, individual and environment of the wasp. Notably, wasps can adjust the chemical composition of their cuticle depending on temperature variations in the environment. As a result of increasing temperature, the number of linear alkanes increases to strengthen desiccation resistance in the cuticle while the number of branched alkanes decreases. A balance in compounds must be attained as no new CHCs are produced; instead, wasps restructure their cuticle depending on the ambient temperature, to enhance its resilience. Inevitably, this also affects wasp communication, but compounds with intermediate melting points help in alleviating this effect as they play a dual role in waterproofing and chemical signaling. (Michelutti et al., 2018) 

Wasp behavior  

The CHCs of wasps have multiple functions beside the above-mentioned ones. They play a role in nestmate recognition, fertility signals amongst females, dominance within a colony, and aggregation. A study on the social organization and ovarian development of three colonies of Polistes dominulus wasps shows that the queens or foundresses of each colony have similar CHCs, while their descendants have less methyl-branched alkanes and linear alkanes in their cuticles. The high ovarian activity of the foundresses and their complex CHCs are a sign of dominance within a colony, and result in the diminished ovarian activity of other female wasps. In each colony studied, only one daughter had a similar cuticular composition to the foundress with comparable ovarian development, signaling her high fertility to other worker wasps. However, this never overrides the dominance of the queen; the daughter would either establish her own colony one day or assume the queen’s role within the native colony in her absence. The other descendants with different cuticular mixtures also had medium-developed ovaries, showing the relationship between CHCs and ovarian activity. This means that variations in CHCs may be under hormonal control. (Bonavita-Cougourdan et al., 1991) 

Contrary to previous beliefs, nestmate recognition is not directly processed by differences in worker wasp CHCs. Rather, it is the nests of social wasps which contain the same hydrocarbons as those on the cuticles of worker wasps (in similar proportions too) that allow for this differentiation (Bonavita-Cougourdan et al., 1991). A study on Polistine wasps shows that nestmates recognize each other by the scent of their nests. This means that newly emerged worker wasps must be exposed to their nest’s odor to recognize their own nestmates and vice-versa. Emerged workers isolated from their nests fail to discriminate between nestmates and non-nestmates as they are not familiar with the odor of their nest and cannot discern their colony odor simply through the chemical components of their cuticle. Instead, they find any colony, adopt its scent and begin their journey as working wasps. Although some wasp species show a high correlation between varying CHC profiles and the acceptance into a colony, the nest odor of species with similar CHC profiles is the main identifying factor for wasp recognition. This also implies that the ability to recognize nestmates involves the intolerance of unfamiliar odors rather than the tolerance of familiar odors. (Singer & Espelie, 1996). 

Deep dive into wasp nests 

Paper wasps in the genus Polsites construct their nests using rotten wood or plant fibers chewed up and mixed with their saliva to form a protein-rich pulp. The saliva of adult wasps acts as an adhesive substance binding with the wood or plant fibers and quickly and irreversibly forming a water insoluble, water repellent substance called carton. They mold this pulp to form the cells of their open nests as seen in Figure 10 (Wikimedia Commons, 2024). In the genus Epiponini from the same species Vespidae, an envelope with multiple layers is built to protect the nest as shown in Figure 11. These nests are suspended by a thick pedicel also built by the wasp and coated with a substance repelling ants (Eaton, 2021). This substance is secreted by their sternal glands and depending on the species, contains methyl hexadecanoate, hexadecanoic acid and/or octadecenoic acid, which all act as repellants.  

Fig 10. Open paper wasp nest without protective envelope (ABC Humane Wildlife Control & Prevention, 2024) 

Fig 11. Inverted wasp nest with multiple paper envelope layers protecting the inner combs. An opening is made in the nest to show the interior. Wasps are placed near the nest to put into perspective the size of the nest. (Schmolz et al., 2000) 

The pedicel has an inner fibrous region mainly composed of cellulose while its outer region is a mixture of oral and sternal glands secretions with a high protein content. Similarly, the nest has a high cellulose content derived from the wood or plant fibers and is rich in proteins found in the wasp’s saliva. Multiple studies analyzed the contents of different social wasp saliva and the results showed a high proportion of the following amino acids: proline, glycine, alanine and serine. The main amino acid detected in nest materials is proline, which is a dominant component in structural proteins providing mechanical strength to the paper nests. (Singer et al., 1991). It is difficult to accurately identify the exact components of the salivary secretion as it is typically mixed with other organic materials found in the nest. Two genera of Polistine wasps, Pseudochartergus and Ropalidia, are known to build nests from pure secretions, and both have been studied. One study shows that the pure secretion in Pseudochartergus is mainly composed of chitin while a different study concludes that the main protein found in Ropalidia pure secretions is β-keratin. While both have different results, it is possible that different species of social wasp simply have different salivary components that act similarly with a high structural protein content (Maschwitz et al., 1990). More recent findings suggest that mucoproteins in the saliva are responsible for its gluing properties as they can form rubbery and sticky gels (Schmolz et al., 2000). 

Nest strength  

As mentioned in the previous sections about long-chain hydrocarbons, both the nest and pedicel have similar composition to the wasp cuticle. A connection can therefore be made between the properties of CHCs and the nest material. Just like the cuticle contains chemical compounds essential for maintaining internal stability, the nest composition may have similar functions in response to environmental changes. It may change its composition to adhere to temperature variations in order to support colony homeostasis or even nest waterproofing. For temperature regulation, the plant fibers in nests conduct solar heat absorbed on the surface during the day to the interior, and at night, they release metabolic heat generated by the wasps from the interior to the outside. If that is not enough, then worker wasps will cool down the nest with water droplets. Moreover, the cellulose and lignin from wood fibers used in nests provide high tensile strength to the nest, overcoming mechanical burdens such as wind. All these aspects put together form the strong and resistant nests of social wasps. (Michelutti et al., 2018) 

Conclusion  

In conclusion, a chemical analysis of wasp venom, pheromones, cuticle and nesting materials demonstrate the finely evolved traits of wasps required for efficient survival and successful interaction within their ecosystems and colonies. Whether it be to hunt or defend their colony against threats, both solitary and social wasps have optimized venom compositions to meet their needs. With venom rich in PLA1 and PLA2, mastoparans and kinins, which cause severe inflammation and allergic reactions enough to paralyze and kill, wasps are well-equipped for interactions with unwanted intruders or prey. It is the synergy of these compounds that ensures the rapid destruction and swelling of tissues, as well as the propagation of venom, enhancing both defensive and predatorial capabilities. Furthermore, wasp pheromones serve as vital communication tools within colonies, regulating reproduction, defense and territorial movement, with species-specific signaling and antennal reception through sensillum pores. Interestingly, while female sex pheromones are not always specie-specific, male wasps have developed a tactic to navigate towards the right species for mating. They have enhanced receptors on their antenna used to follow the concentration gradient of these sex pheromones to find the right partner. While male wasps overcome this problem, some find themselves with another one: mirror orchids. This plant takes advantage of the male wasp by emanating a scent and appearance strikingly similar to that of the female wasp, luring in the male wasp for mating and successfully getting pollinated. This showcases the cycle of design solutions evolved by each species to ensure its survival in the environment. Moreover, trail pheromones are used among social wasp communities to guide other nestmates to food sources and new nesting sites. While these pheromones don’t last quite long, they’ve developed similar pheromones that are long-lasting. They are mainly used for marking territorial routes, which is important in maintaining stability amongst surrounding wasp colonies. Their strategic use of pheromones reflects the highly coordinated nature of wasp societies. Additionally, CHCs ensure desiccation resistance while also assisting in chemical signaling such as nestmate recognition and hierarchical structure determination within colonies. To defeat the heat during hot seasons, their cuticle changes composition with respect to temperature variations in order to maintain their optimal temperature. The number of linear alkanes increases to improve desiccation resistance, while the number of branched alkanes decreases as a result. Finally, their nest-building strategies, combining wood fibers with protein-rich saliva, result in strong, thermoregulated structures crucial for colony survival. While wasps with similar CHCs cannot identify one another merely from their cuticular composition, they use the scent of their nest which matches their CHCs. In that sense, nestmate recognition is based on the intolerance of unfamiliar nest odors. Collectively, these elements showcase the evolutionary balance of biochemical and behavioral adaptations that enable wasps to thrive across diverse environments.  

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