Cuticular Chemical Profiles Research Articles

Low Intraspecific Aggression Level, Cuticular Hydrocarbons, and Polydomy in the Bullet Ant.

Ants use chemical cues known as cuticular hydrocarbons (CHCs) for both intraspecific and interspecific recognition. These compounds serve ants in distinguishing between nestmates and non-nestmates, enabling them to coexist in polydomous colonies characterized by socially connected yet spatially separated nests. Hence, the aim of this study was to investigate the intraspecific aggression level between nestmates and non-nestmates of the bullet ant Paraponera clavata (Fabricius, 1775), analyze and compare their CHCs, and evaluate the occurrence of polydomy in this species. We conducted aggression tests between foragers, both in laboratory and field settings. To identify the chemical profiles, we utilized gas chromatography coupled with mass spectrometry (GC-MS). We marked the foragers found at nest entrances and subsequently recaptured these marked ants to validate workers exchange among nests. Across all nests, a low intraspecific aggression level was observed within the same area. However, a significant difference in aggression correlated to distance between nests. Analysis of the cuticular chemical profile of P. clavata unveiled colony-specific CHCs, both qualitatively and quantitatively. Notably, we observed instances of ants from certain nests entering or exiting different nests. This behavior, in conjunction with the observed low intraspecific aggression despite differences in CHCs suggests polydomy for this species. Polydomy can offer several benefits, including risk spreading, efficient exploitation of resources, potential for colony size increasing and reduced costs associated with foraging and competition.

Nestmate Recognition in Two Melipona Stingless Bee Species: The Effect of Cuticular Chemical Profiles and Colony Distance

Nestmate Recognition in Two Melipona Stingless Bee Species: The Effect of Cuticular Chemical Profiles and Colony Distance

Cuticular lipid profiles of selected species of cyclocephaline beetles (Melolonthidae, Cyclocephalini).

Neotropical cyclocephaline beetles, a diverse group of flower-loving insects, significantly impact natural and agricultural ecosystems. In particular, the genus Cyclocephala, with over 350 species, displays polymorphism and cryptic complexes. Lacking a comprehensive DNA barcoding framework, accessible tools for species differentiation are needed for research in taxonomy, ecology, and crop management. Moreover, cuticular hydrocarbons are believed to be involved in sexual recognition mechanisms in these beetles. In the present study we examined the cuticular chemical profiles of six species from the genus Cyclocephala and two populations of Erioscelis emarginata and assessed their efficiency in population, species, and sex differentiation. Overall we identified 74 compounds in cuticular extracts of the selected taxa. Linear alkanes and unsaturated hydrocarbons were prominent, with ten compounds between them explaining 85.6% of species dissimilarity. Although the cuticular chemical profiles efficiently differentiated all investigated taxa, only C. ohausiana showed significant cuticular profile differences between sexes. Our analysis also revealed two E. emarginata clades within a larger group of 'Cyclocephala' species, but they were not aligned with the two studied populations. Our research underscores the significance of cuticular lipid profiles in distinguishing selected cyclocephaline beetle species and contemplates their potential impact as contact pheromones on sexual segregation and speciation.

Understanding the ability of Pachycrepoideus vindemiae (Hymenoptera: Pteromalidae) to find and parasitize buried Diptera pupae in southwestern Colombia

Pachycrepoideus vindemiae is a generalist wasp parasitoid released for biological control of the pupal stage for several species of Tephritoidea and Muscoidea flies that limit production of fruits and poultry commodities, respectively, worldwide. The parasitoid wasp must find buried host pupae to oviposit on them, and several factors may influence this outcome. The objectives of this study were to determine the capacity of first, host larvae to burrow to pupate according to substrate humidity and second, the parasitoid wasp to burrow and parasitize buried host pupae according to different conditions (substrate type, host species and parasitization time exposure). Moreover, comparison of chemical profiles between host’s pupae potentially involved for host location by the parasitoid was realized by GC-FID. Peat humidity significantly affected the burrowing depth of Dasiops inedulis and Anastrepha striata and both species buried significantly deeper in peat with 50% humidity than in dry conditions. The number of emerged parasitoids is not different between the two tested host species. P. vindemiae performance was better in peat than in crop soil. In peat wasps’ parasitism is similar between buried pupae located at 0 mm or 10 mm depth regardless of the time of exposure to the parasitoid. Cuticular chemical profiles showed that the four-host pupa species studied did not share compounds. However, A. striata shared some compounds with D. inedulis and, M. domestica shared some with C. capitata. Common compounds were found in the extracts of parasitized and non-parasitized pupae of C. capitata, D. inedulis and M. domestica.

A predatory social wasp does not avoid nestmates contaminated with a fungal biopesticide.

Fungus-based biopesticides have been used worldwide for crop pest control as a safer alternative to chemical pesticides such as neonicotinoids. Both agrochemicals can be lethal and may also trigger side effects on the behavioral traits of non-target social insects, which play a crucial role in providing essential biological pest control services in agroecosystems. Here, we evaluated whether a commercial formulation of the entomopathogenic fungus Beauveria bassiana or the neonicotinoid imidacloprid causes mortality in foragers of Mischocyttarus metathoracicus. These social wasps are natural enemies of caterpillars and other herbivorous insects and inhabit both urban and agricultural environments in Brazil. We also tested whether wasps discriminate between biopesticide-exposed and unexposed conspecifics. Through a combination of laboratory (survival assay) and field experiments (lure presentation), along with chemical analyses (cuticular hydrocarbon profiles), we showed that topic exposure to the label rate of each pesticide causes a lethal effect, with the biopesticide exhibiting a slower effect. Moreover, wasps do not discriminate biopesticide-exposed from unexposed conspecifics, likely because of the similarity of their cuticular chemical profiles 24h after exposure. Overall, the delayed lethal time at the individual level, combined with the indistinctive chemical cues of exposure and the lack of discrimination by conspecifics suggests that the fungal biopesticide may ultimately pose a threat to the colony survival of this predatory wasp.

Land-use stress alters cuticular chemical surface profile and morphology in the bumble bee Bombus lapidarius.

Pollinators and other insects are currently undergoing a massive decline. Several stressors are thought to be of importance in this decline, with those having close relationships to agricultural management and practice seemingly playing key roles. In the present study, we sampled Bombus lapidarius L. workers in grasslands differing in their management intensity and management regime across three different regions along a north-south gradient in Germany. We analyzed the bees with regard to (1) their cuticular hydrocarbon profile (because of its important role in communication in social insects) and amount of scent by using gas chromatography and (2) the size of each individual by using wing distances as a proxy for body size. Our analysis revealed changes related to land-use intensity and temperature in the cuticular scent profile of bumble bees. Decreasing body size and increasing total scent amount were explained by an interaction of land-use intensity and study region, but not by land-use intensity alone. Thus, land-use intensity and temperature influence intracolonial communication and size, both of which can have strong effects on foraging. Land management and climate are therefore probably detrimental for colony maintenance and the reproductive success of bumble bees.

Anthropic action affects the cuticular chemical profile of social wasps

As a result of environmental change by anthropic action, animal species that inhabit these areas may suffer the effects of it on their phenotypes as a consequence of adapting to these conditions. In the case of social wasps, cuticular chemical compounds may be influenced, since these vary depending on genetic and environmental factors. However, few studies have investigated the synanthropic effects over the cuticular surface of social wasps. Therefore, the aim of this study was to investigate how cuticular compounds vary according to the different degrees of human activity and test the hypothesis that cuticular compounds of social wasps are affected by the level of anthropic activity in which their nests are found. Data on the cuticular chemical compounds composition of colonies of 3 species of social wasps were used along with the level of anthropization of their nesting sites in four municipalities in the state of Mato Grosso do Sul, Brazil. From the geographical coordinates of the sampling sites, the percentages of urban construction areas, agriculture, water body, vegetation and exposed land were calculated, and the nesting sites of the colonies were classified as more or less anthropized areas. The chemical profile was determined by extraction of cuticular compounds and analyzed by Gas Chromatography coupled to Mass Spectrometer (GC-MS). The results show that the cuticular chemical composition of the individuals of these species is affected by the level of anthropization in their nesting sites, with a qualitative and quantitative variation that must be tied not only to genetic differences, but, above all, to the local environmental conditions to which their colonies are subjected.

Small hive beetle, Aethina tumida (Coleoptera: Nitidulidae): chemical profile of the cuticle and possible chemical mimicry in a honeybee (Apis mellifera) pest

The small hive beetle, Aethina tumida (Coleoptera: Nitidulidae), is an economically important pest of the Western honeybee, Apis mellifera (Hymenoptera: Apidae). We investigated the effect of rearing environment on the cuticular chemical profile of adult A. tumida, using hexane to extract the hydrocarbons and other compounds from the cuticles of beetles. Beetles were collected from A. mellifera colonies in Australia as well as reared in single sex laboratory cultures on different diets. We investigated whether rearing environment (laboratory vs. field, different apiaries, access to mating partners, diet) had any effect on cuticular hydrocarbons. Coupled gas chromatography–mass spectrometry analyses of the extracts showed that rearing environment had significant qualitative and quantitative effects on the hydrocarbons detected. The data support the hypothesis that cuticular profiles of A. tumida are contingent on environment, partitioning on the basis of rearing diet and source hives. The finding has implications for the regulation of interactions between A. tumida and honeybees and improvements in targeting of management strategies.

Deciphering the chemical phenotype in Atta laevigata (Smith, 1858) (Hymenoptera: Formicidae): A relationship between polymorphism and cuticular hydrocarbons

In the Attina subtribe the division of labor among workers is based on different tasks performed by morphological subcastes. Considering that cuticular chemical compounds play important roles as protection against water loss and mediates interactions between nestmates, and that studies on the cuticular chemical profile of ants of the genus Atta are still scarce, the aim of this study was to evaluate the relationship between morphological and chemical phenotypes in the subcastes of Atta laevigata (Smith, 1858) workers. The cuticular chemical composition of the different subcastes was assessed by Gas Chromatography coupled to Mass Spectrometry technique. The compounds found in the cuticle of the different subcastes had carbon chain size between 18 and 31 atoms, with higher content of linear alkanes in workers and soldiers and higher content of branched alkanes in gardeners and generalists, probably related to the type of tasks they perform in their colonies, since some workers perform more intra- or extranidal tasks in relation to others. The results show significant qualitative differences in the cuticular composition of the different subcastes, with a greater relationship between them according to the environmental restrictions that each subcaste is more subjected to due to the role played in the colony.

Resin Use by Stingless Bees: A Review.

Simple SummaryBees, ants, and other insects harvest antimicrobial resins from plants and use this material for a variety of purposes, from nest construction to defense against predators and pathogens. Resin use is thought to have facilitated the evolution of sociality in stingless bees, and today, resin use remains fundamentally important for stingless bee colony function. Most species use resin to build brood comb, storage pots for honey and pollen, and various protective structures within the nest. Many also use resin to protect their nests from predators, fortifying nest entrances with a barrier of sticky resin droplets or applying resin directly to would-be invaders. For some species, the presence of resin inside the nest space can also influence the physical properties of the bees themselves, enriching the chemical composition of the outermost layer of their exoskeleton, and possibly shaping the communities of bacteria and fungi that are found on the bees, and in their nests. This article brings together studies from a variety of fields to illustrate the importance of resin use for stingless bee colony function and conservation, and to point towards areas of future research.Stingless bees (Meliponini) are highly social bees that are native to tropical and sub-tropical ecosystems. Resin use is vital to many aspects of stingless bee colony function. Stingless bees use resin to build essential nest structures, repel predators, and kill would-be invaders. Furthermore, resin-derived compounds have been found to enrich the cuticular chemical profiles of many stingless bee species, and resin may play an important role in shaping the microbial communities associated with stingless bees and their nests. Despite its importance for colony function, previous reviews of resin use by stingless bees are lacking. This topic grows increasingly urgent as changes in beekeeping and land use practices occur, potentially diminishing stingless bees’ ability to incorporate resin into the nest environment. In this article, we review existing literature on resin use by stingless bees and discuss potential areas of future research.

Juvenile hormone affects age polyethism, ovarian status and cuticular hydrocarbon profile in workers of the wasp Polybia occidentalis.

Division of labor is one of the most striking features in the evolution of eusociality. Juvenile hormone (JH) mediates reproductive status and aggression among nestmates in primitively eusocial Hymenoptera (species without morphologically distinct castes). In highly social species it has apparently lost its gonadotropic role and primarily regulates the division of labor in the worker caste. Polybia occidentalis, a Neotropical swarm-founding wasp, is an ideal model to understand how JH levels mirror social context and reproductive opportunities because of the absence of a clear morphological caste dimorphism. In this study, we tested the hypothesis that JH influences division of labor, ovary activation and cuticular hydrocarbon profiles of workers. Our observations confirmed that a JH analog (methoprene) and an inhibitor of JH biosynthesis (precocene) affected the cuticular chemical profile associated with age polyethism. Also, methoprene and precocene-I treatment of females influenced ovarian activation differently (individuals treated with methoprene expressed more activated ovaries while precocene treatment did not have significant effect). These results suggest that different hormonal levels induce a differential expression of cuticular chemicals associated with workers' age polyethism, which may be essential for keeping the social cohesion among workers throughout their lives in the colony. Furthermore, JH is likely to play a gonadotropic role in P. occidentalis. JH has apparently undergone certain modifications in social Hymenoptera, presenting multifaceted functions in different species.

Persistence and diffusion behaviour of chlorpyrifos in five different species of vegetables: A comparative analysis

Understanding of pesticide persistence and diffusion on the fresh vegetables are extremely important in food safety and decontamination process. In this study, we examine the persistence and diffusion behaviour of chlorpyrifos pesticide in five different species of vegetables. The chlorpyrifos pesticide was spiked on the vegetable surfaces and the extracted samples from peel and tissues were subjected to Gas Chromatography equipped with a Flame Photometric Detector (GC-FPD). Further, the chlorpyrifos diffusion behaviour was compared with the osmotic potential, shear strength, cuticular chemical profile and microstructure of peel surface of vegetables. The persistence analysis results revealed that chlorpyrifos level was decreased in peel surface and diffusion rate was increased in inner tissue with respect to durations. Within 72 h exposure, chlorpyrifos reached 0.7 cm depth into the inner tissue of vegetables. Significant level of chlorpyrifos diffusion with P ≤ 0.05 was observed in beetroot (2.47%), khon khol (1.46%) and brinjal (0.92%) compared to cucumber and potato. Remarkably, there was no direct linkage between the chlorpyrifos diffusion rate, osmotic potential and toughness of vegetables. In addition, the Gas Chromatography Mass Spectroscopy (GC-MS) and Scanning Electron Microscopy (SEM) analyses revealed that epicuticular surface microstructure and chemical profiles were not correlated with the chlorpyrifos diffusion in all the tested vegetables. The study results concludes that chlorpyrifos diffusion is vegetable species specific and it is highly variable between the species.

Effect of Larval Topical Application of Juvenile Hormone on Cuticular Chemical Composition of Mischocyttarus consimilis (Vespidae: Polistinae) Females

Juvenile Hormone (JH) is considered the main determinant of caste in social insects, though little is known about how this hormone acts in social wasps, especially the independent-founding species. The known relationship between JH titer and caste in the colony and we suggest a relationship among the effects of JH and the cuticular chemical profile. Therefore, this study aimed to test the hypothesis that topical application of JH to larvae of different instars alters the cuticular chemical composition of newly emerged females of Mischocyttarus consimilis (Zikán), influencing the dynamics of colony. Two techniques were used to evaluate the variation in cuticular chemical composition: Fourier transform infrared photoacoustic spectroscopy and gas chromatography coupled to mass spectrometry (GC-MS). Indeed, the application of JH did significantly alter the cuticular chemical composition of adult females that received treatment at the larval stage in comparison to control. The effects of JH were instar-dependent in that the results of topical application were significant when performed at third larval instar. Overall, these results add evidence that caste determination may, at least in part may be pre-imaginal in species of independent-founding social wasps.

New approach to application of mid-infrared photoacoustic spectroscopy in forensic analysis: Study with the necrophagous blow fly Chrysomya megacephala (Diptera: Calliphoridae)

Insects can provide clues in a variety of ways to assist in criminal investigations. The FTIR-PAS technique has been successfully used to assess the cuticular chemical profiles of insect samples from different groups and for several goals. However, until now, it has never been used to evaluate samples of forensic interest, despite providing faster results, compared to the methods currently used. In this study, mid-infrared photoacoustic spectroscopy was employed to assess the cuticular chemical profiles of different stages of development of the blow fly Chrysomya megacephala sampled from two distinct populations. The results showed that this technique enabled detection of significant differences between the main vibrational modes of the chemical bonds present in the cuticles of the two populations and the different stages of development of the fly. The method enables identification of the age of individuals collected at the crime scene, as well as the distinction of different populations. Therefore, this methodology could assist in forensic investigations, in both estimating the Postmortem Interval and determining the location where the crime occurred, or whether the body had suffered some type of translocation. The technique provides high reproducibility and fast analysis, so its application for analysis of C. megacephala is a viable option in forensic crime investigations.

Discovery of an acoustically locating parasitoid with a potential role in divergence of song types among sympatric populations of the bush cricket Mecopoda elongata

The bush cricket Mecopoda elongata provides a striking example of sympatric intraspecific divergence in mating signals. Five completely distinct song types are found in various parapatric and sympatric locations in South India. While there is convincing evidence that population divergence in M. elongata is being maintained as a result of divergence in acoustic signals, cuticular chemical profiles, and genital characters, the causes of the evolution of such divergence in the first place are unknown. We describe the discovery of a tachinid parasitoid with an orthopteroid hearing mechanism affecting M. elongata. This parasitoid may have a role in driving the extraordinary divergence that had occurred among M. elongata song types. Over two years we sampled individuals of three sympatric song types in the wild and retained individuals in captivity to reveal rates of parasitization. We found that all three song types were infected with the parasitoid but that there were significant differences among song types in their probability of being infected. The probability of tachinid parasitization also differed between the two sampling periods. Therefore, it is possible that parasitoid infection plays a role in song type divergence among sympatric bush cricket populations.

Intraspecific Cuticular Chemical Profile Variation in the Social Wasp Mischocyttarus consimilis (Hymenoptera, Vespidae).

Chemical compounds present on the cuticle of social insects are important in communication, as they are used in recognition of nestmates and sexual partners as well as in caste distinction, varying according to several factors, such as genetic and environmental. In this context, some studies have explored the cuticular chemical profile as a tool for assessing intra- and interspecific differences in social insects, although few studies have investigated this in social wasps. This study aimed to assess the differences in cuticular chemical profiles among different geographic samples of the wasp Mischocyttarus consimilis Zikán. Our hypothesis was that environmental factors are decisive to compose the cuticular chemical profiles of colonies of these social wasps and that there are differences regarding the geographic distribution among colonies. We used Fourier Transform Infrared-Photoacoustic Spectroscopy (FTIR-PAS) to assess the chemical profiles of samples. Our results show that despite there are differences between the cuticular chemical composition of the wasps' samples from different populations, there is no significant correlation compared to the spatial distribution of the colonies nor with the environment. Thus, our hypothesis was refuted, and we can infer that in this species neither exogenous nor genetic factors stand out to differentiate the chemical signature of their colonies, but a combination of both.

CHEMICAL PROFILE OF ORGANIC COMPOUNDS PRESENTED IN THE CUTTLE OF MALES AND FEMALES OF THE SPECIES Pachycoris torridus (SCOPOLI, 1772) (Hemiptera: Scutelleridae) SUBMITTED OR NOT ANESTHETIC PROCEDURE AND IN DIFFERENT TIMES

Pachycoris torridus (Scopoli, 1772) (Hemiptera: Scutelleridae) is the main pest of the Jatropha curcas (Linnaeus) (Euphorbiaceae) specie. The study of cuticular compounds of this pest is an alternative for understanding their intraspecific chemical communication in an attempt to develop methods to their behavioral control. This study has as objective to detect variations of the chemical profile of organic compounds contained in the cuticle of P. torridus at different times and extraction method. An adult of each genus of the P. torridus specie, with normal behavior and basic chromatic patterns, was immersed separately in a glass vial (10mL) containing 2mL of HPLC grade hexane bidestilado for 10 seconds (with/without previous anesthesia) and 10 minutes (with/without previous anesthesia), with four replications per treatment. After this time, the extract was gathered and placed in a 1.5mL vial and then in a freezer at -20°C. 1μl aliquots of the extracts (n=32) were analyzed in a gas chromatograph coupled to a mass spectrometry (GC-MS). The chemical evaluation was focused on the concentrations of the volatile compounds [(E)-2-hexenal (E)-4-(oxo)-2-hexenal, (E)-2-hexenil acetate, (E)-2-Octenal, undecane, dodecane, 1-tridecene, unknown, tridecane, (Z,Z)-2,7-octadien1-ol acetate, Tetradecane and Tetradecanal] identified in the extracts. Finally, the cuticular chemical profiles of the major compounds [(E)-2-Hexenal, Tridecane and (E)-4-(oxo)-2-Hexenal] of males and females of the P. torridus specie was the same. As to preparation of extracts protocol, it is recommended to use the immersion of the entire body of the insect at both times (10 seconds and 10 minutes) without anesthesia, in order to enlarge the detection of compounds.

Dear Enemy Phenomenon in the Ant Ectatomma brunneum (Formicidae: Ectatomminae): Chemical Signals Mediate Intraspecific Agressive Interactions

The integrity of ant colonies depends exclusively on social relationships between their individuals, especially the ability of communication between group members, which is mainly mediated through chemical signals. Another important feature of ant behavior is territory defense, since they need to gather large amounts of food to feed their larvae, males and breeding females. Thereby, ants might display behavioral strategies to defend their territories from intruders. Here we investigated whether Ectatomma brunneum displays the Dear Enemy Phenomenon, what is the relationship between Cuticular Hydrocarbon composition and levels of aggression during their intraspecific interactions and which compounds and/or classes of compounds might be the most important to modulate the level of aggression. To test our hypothesis, we evaluated the levels of aggression through behavioral observations during interactions between 23 pairs of colonies nested in two distinct sites at varied distances. Then, we analyzed the cuticular chemical profile of the individuals involved in the interactions, and compared these results with the levels of aggression displayed between colonies tested. The results allow us to confirm our hypothesis that the DEP occurs in E. brunneum. The higher tolerance between closer colonies can be explained due to their kinship level in addition to sharing the same microhabitats. The results also showed there are significant differences in CHCs profiles, especially between colonies nested at relatively greater distances, and it is likely that differences in content of some branched alkanes are the most important to establish these differences and, therefore, the levels of aggression during the interactions.

Habitats shape the cuticular chemical profiles of stingless bees

Stingless bees are highly social pollinators in tropical ecosystems. Besides floral pollen and nectar, they collect substantial amounts of plant resins, which are used for nest construction/maintenance and defence against antagonists. Moreover, some stingless bees extract chemical compounds from resins and incorporate them in their cuticular chemical profiles, rendering this trait directly dependent on the plant community of the surrounding environment. While previous studies have investigated how variation in the composition and diversity of available resin sources affect resin storages inside hives, subsequent effects on the bees’ cuticular chemistry have not been studied. To fill this gap, we investigated the number, proportion and composition of compounds in the cuticular chemical profile of an Australian stingless bee using gas chromatography and mass spectrometry. We analysed whether and (if so) how the cuticular chemistry was affected by habitat (i.e., plantations, forests, and gardens) and tree species richness. We found that overall numbers and proportions of self-produced and resin-derived compounds in the cuticular chemical profiles of Tetragonula carbonaria were similar across habitats, while the composition of all compounds (i.e., both self-produced and resin-derived) and of resin-derived compounds differed between habitats. This indicates that the surrounding tree species community and thus available resin chemistry affected the composition of particularly resin-derived compounds on the bees’ cuticle. As the number and composition of resin-derived cuticular compounds were not affected by tree species richness, stingless bees appear to selectively incorporate specific compounds available in the surrounding environment in their cuticular chemical profiles, which may increase their defensive properties.

Evolution of Caste-Specific Chemical Profiles in Halictid Bees.

Chemical communication is crucial for the maintenance of colony organization in eusocial insects and chemical signals are known to mediate important aspects of their social life, including the regulation of reproduction. Sociality is therefore hypothesized to be accompanied by an increase in the complexity of chemical communication. However, little is known about the evolution of odor signals at the transition from solitary living to eusociality. Halictid bees are especially suitable models to study this question as they exhibit considerable variability in social behavior. Here we investigated whether the dissimilarities in cuticle chemical signals in females of different castes and life stages reflect the level of social complexity across halictid bee species. Our hypothesis was that species with a higher social behavior ergo obligate eusocial species possess a more distinct chemical profile between castes or female life stages. We analyzed cuticular chemical profiles of foundresses, breeding females and workers of ancestrally solitary species, facultative and obligate eusocial halictid species. We also tested whether social complexity was associated with a higher investment in chemical signals. Our results revealed higher chemical dissimilarity between castes in obligate than in facultative eusocial species, especially regarding macrocyclic lactones, which were the single common compound class overproduced in queens compared with workers. Chemical dissimilarities were independent of differences in ovarian status in obligate eusocial species but were dependent on ovarian status in facultative eusocial species, which we discuss in an evolutionary framework.