Chemical mimicry in an incipient leaf-cutting ant social parasite

Some social parasites of insect societies are known to use brute force when usurping a host colony, but most use more subtle forms of chemical cheating either by expressing as few recognition cues as possible to avoid being recognized or by producing similar recognition cues to the host to achieve positive discrimination. The former “chemical insignificance” strategy represents a more general adaptive syndrome than the latter “chemical mimicry” strategy and is expected to be characteristic of early evolutionary stages of social parasitism. We tested this hypothesis by experimentally analyzing the efficiency by which Acromyrmex echinatior leaf-cutting ants recognize intruding workers of the incipient social parasite Acromyrmex insinuator. The results were consistent with the parasite being “chemically insignificant” and not with the “chemical mimicry” hypothesis. Gas chromatography–mass spectrometry analysis of cuticular hydrocarbon profiles showed that social parasite workers produce significantly fewer hydrocarbons overall and that their typical profiles have very low amounts of hydrocarbons in the “normal” C29–C35 range but large quantities of unusually heavy C43–C45 hydrocarbons. This suggests that the C29–C35 hydrocarbons are instrumental in normal host nestmate recognition and that the C43–C45 compounds, all of which are dienes and thus more fluid than the corresponding saturated compounds, may reinforce “chemical insignificance” by blurring any remaining variation in recognition cues.     

Food influence on colonial recognition and chemical signature between nestmates in the fungus-growing ant <Emphasis Type="Italic">Acromyrmex subterraneus subterraneus</Emphasis>

Summary. Neotropical Fungus-growing leaf-cutting ants (tribe Attini) live in obligatory symbiosis with a fungus, which they grow on fresh leaves harvested by workers. Colonial recognition is likely based on chemical cues provided by cuticular hydrocarbons that have been found to be partly influenced by environmental odor sources. The diet breadth of Acromyrmex subterraneus subterraneus enabled us to test the impact of different plant diets on colonial recognition. The intermediary of the fungus in the ants feeding habit adds a special angle to the question. From a queenright (QR) mother colony of A. s. subterraneus we formed several groups of queenless (QL) workers with fungus (approx. 700 ants). The QR colony and two of the QL-groups were fed with the same diet of fresh bramble leaves. Two other QL-groups were fed with privet leaves and two with rose flowers. After 4 months, QR workers were significantly more aggressive towards the QL-group fed with rose flowers or privet leaves than towards workers of the QL-groups fed with fresh bramble leaves. Rose-fed QL workers were aggressive towards privet-fed QL workers and vice versa, but never towards workers of their counterpart group that fed on the same diet. These results suggest that the absence of the queen or the separation time between groups played a minor role in shaping nestmate recognition cues as compared to the diet. The behavioral studies were supplemented by chemical analyses of cuticles, postpharyngeal glands (PPG) and plant-food extracts revealing profiles variations that were correlated with the dietary changes. However, although the plant extract contained several hydrocarbons there was no congruency between the plant profile and the respective diet-group ants. These results support the hypothesis that the diet influences indirectly the chemical profiles and consequently the recognition cues in A. s. subterraneus.     

Colonial recognition of fungus in the fungus-growing ant Acromyrmex subterraneus subterraneus (Hymenoptera: Formicidae)

Summary. Leaf cutting ants live in symbiosis with a basidiomycete fungus that is exploited as a source of nutrients for the ant larvae. Tests of fungus transport demonstrated that Acromyrmex subterraneus subterraneus workers discriminate concolonial fungus from alien fungus, and rejected the latter. Larvae and pupae of the ant were used as controls. Chemical analysis of the fungus revealed a great similarity between its hydrocarbon profile and that found on the ant brood. Experiments with lures showed that chemical extracts from the fungus are responsible for this discrimination process. Moreover, the presence of brood inside the fungus seemed to be important for discrimination of the fungus by workers. Resident workers accepted concolonial broodless fungus less than concolonial fungus inoculated with brood odor. Fungus seems to acquire colonial odor passively, simply by contact with the brood. The impact of fungus volume present in the nest on closure of the colony is discussed. We show here for the first time the importance of a symbiotic vegetal organism in colonial recognition in social insects. Received 14 April 2000; accepted 29 September 2000     

Disease resistance in a weaver ant, <Emphasis Type="BoldItalic">Polyrhachis dives</Emphasis>, and the role of antibiotic-producing glands

Parasites represent one of the main threats to all organisms and are likely to be particularly significant for social animals because of the increased potential for intragroup transmission. Social animals must therefore have effective resistance mechanisms against parasites and one of the most important components of disease resistance in ants is thought to be the antibiotic-producing metapleural gland. This gland is ancestral in ants, but has been lost secondarily in a small number of species. It is unknown whether these evolutionary losses are due to a reduction in parasite pressure or the replacement of the gland’s function with other resistance mechanisms. Here we used the generalist entomopathogenic fungus Metarhizium to compare the disease resistance of a species of a weaver ant, Polyrhachis dives, which has lost the metapleural gland, with that of the well-studied leaf-cutting ant Acromyrmex echinatior and two other ant species, Myrmica ruginodis and Formica fusca, all of which have metapleural glands. The P. dives weaver ants had intermediate resistance when kept individually, and similar resistance to A. echinatior leaf-cutting ants when kept in groups, suggesting that the loss of the metapleural gland has not resulted in weaver ants having reduced disease resistance. P. dives weaver ants self-groomed at a significantly higher rate than the other ants examined and apparently use their venom for resistance, as they had reduced resistance when their venom gland was blocked and the venom was shown in vitro to prevent the germination of fungal spores. Unexpectedly, the leaf-cutting ant A. echinatior also had reduced resistance to Metarhizium when its venom gland was blocked. It therefore appears that the evolutionary loss of the metapleural gland does not result in reduced disease resistance in P. dives weaver ants, and that this at least in part may be due to the ants having antimicrobial venom and high self-grooming rates. The results therefore emphasise the importance of multiple, complementary mechanisms in the disease resistance of ant societies.     

Experimental evidence for the costs and hygienic significance of the antibiotic metapleural gland secretion in leaf-cutting ants

The paired exocrine metapleural glands present in the large majority of ant species produce compounds with antibiotic properties. In the leaf-cutting ant, Acromyrmex octospinosus, the secretion consists of more than 20 different compounds and it has generally been assumed that the glands serve as a general defence against various infectious microbes of fungal and bacterial origin. We present results illuminating the direct costs and benefits of these metapleural gland defences in A. octospinosus. We show that major workers of this leaf-cutting ant experience a significant reduction in their respiration rate when the metapleural glands are experimentally closed, indicating that metapleural gland secretion incurs a substantial cost and that the production of compounds from these glands is terminated when the ants are incapable of secreting them. In another set of experiments, we show that the ability to secrete antibiotic compounds from the metapleural glands is of significant importance when ants are exposed to a general but potentially virulent insect pathogen, Metarhizium anisopliae. Infection with this fungus is lethal within a few days when ants have their metapleural glands experimentally closed, but relatively harmless when the metapleural glands are functional. These findings support experimentally the view that the metapleural glands play an important hygienic role in leaf-cutting ants.     

The evolution of uniparental transmission of fungal symbionts in fungus-growing termites (Macrotermitinae)

Mutualistic associations between different organisms are theoretically expected when the interests of independently reproducing units are aligned to form a single reproductive unit. This alignment does not come about easily, because models show that hosts and symbionts can be in conflict over the transmission of symbionts. Selection will favour hosts that are able to limit genetic variation of symbionts, for example by enforcing uniparental vertical transmission, while symbionts will be selected to disperse independently of the host. A crucial factor determining the evolution and elaboration of symbiotic relationships is therefore who controls the transmission of symbionts. In the fungus-growing termites (Macrotermintinae) horizontal transmission seems to be the rule as the termites normally acquire their cultivated fungus (Termitomyces) from the environment. In spite of this general pattern, uniparental, vertical transmission has evolved in two unrelated Macrotermitinae genera, where only one sex of the two primary reproductives carries asexual spores from the fungal comb of its parent colony to inoculate the new fungus comb. Remarkably, symbiont transmission is exclusively paternal in Macrotermes bellicosus, whereas symbionts are maternally inherited in all Microtermes species studied so far. Thus, in Macrotermitinae horizontal transmission is the ancestral state with two independent origins to uniparental, vertical transmission. This is in contrast to fungus-growing ants where uniparental, vertical transmission is the rule. Causes and consequences of this difference are further discussed. Despite this fundamental difference both groups evolved a similar symbiosis that is probably the key for their ecological success: the fungus-growing ants in the neotropics and the fungus-growing termites in the paleotropics.     

Ontogeny of nestmate recognition cues in the red carpenter ant (Camponotus floridanus)

Summary A combination of behavioral and chemical analyses was used to investigate the nature of nestmate recognition cues and the effects of worker age and social experience on these cues in the ant Camponotus floridanus. Five categories of workers were tested: foragers, 5-day old and 0-day old callows, 5-day old and 0-day old naive callows. Bioassays consisted of introductions of dead workers from these categories into their own colonies or into an alien colony after the following treatments: 1) killed by freezing, 2) solvent-washed, 3) solvent-washed and coated with a nestmate soak, 4) solvent-washed and coated with a non-nestmate soak. Soaks were obtained from individual ants immersed in hexane and were applied individually to washed workers from the same category. Soaks were analyzed by gas chromatography (GC) and compared by multivariate analyses. Freeze-killed workers from each category elicited more aggressive behavior in the alien colony than in its own. By comparing GC profiles, a worker from any category can be assigned to its colony of origin. Thus all studied worker categories are colony-specific. Solvent-washed ants did not induce more aggressive behaviors in the alien colony than in their own, but they induced significantly less aggressivity in an alien colony than non-treated dead ants from the same category. Washed ants indced more aggressive behaviors when coated with a soak from a different colony as opposed to a soak from the colony in which they were introduced. The combination of behavioral and chemical results lead to the following conclusions: 1) Information contained in soak derived from workers was sufficient to allow nestmate recognition. 2) Nestmate recognition cues, and consequently the recognition response displayed to their bearer, change with age. 3) Social experience is necessary to develop or acquire a colony-specific label. The role of age and social experience on nestmate recognition in social Hymenoptera is discussed.     

Transitioning from unstable to stable colony growth in the desert leafcutter ant Acromyrmex versicolor

Like organisms, cohesive social groups such as insect colonies grow from a few individuals to large and complex integrated systems. Growth is driven by the interplay between intrinsic growth rates and environmental factors, particularly nutritional input. Ecologically inspired population growth models assume that this relationship remains constant until maturity, but more recent models suggest that it should be less stable at small colony sizes. To test this empirically, we monitored worker population growth and fungal development in the desert leafcutter ant, Acromyrmex versicolor, over the first 6 months of colony development. As a multitrophic, symbiotic system, leafcutter colonies must balance efforts to manage both fungus production and the growth of the ants consuming it. Both ants and fungus populations grew exponentially, but the shape of this relationship transitioned at a size threshold of 89?±?9 workers. Above this size, colony mortality plummeted and colonies shifted from hypometric to hypermetric growth, with a distinct stabilization of the relationship between the worker population and fungus. Our findings suggest that developing colonies undergo key changes in organizational structure and stability as they grow, with a resulting positive transition in efficiency and robustness.     

Ant gardens: interspecific recognition in parabiotic ant species

 In French Guiana, parabiotic societies (natural mixed colonies) are frequently found in ant gardens. Crematogaster limata parabiotica (Myrmicinae), often associated with Camponotus femoratus (Formicinae), was found for the first time in parabiosis with ponerine ants: Pachycondyla goeldii and Odontomachus mayi. A detailed study of the relationships between Cr. l. parabiotica and O. mayi showed that each species is aggressive towards allospecific or conspecific individuals belonging to another colony, but tolerates allospecific individuals from the multi-species society. Studies of cuticular substances of the four ant species were made using gas chromatography. The results showed that each species, living alone or in parabiosis, possesses a specific chemical profile. Thus, the ants are able to recognise nestmate and non-nestmate individuals of the associated species, even though their cuticular profiles are different. The hypothesis that the nestmate allospecific profile is learned is suggested to explain this pattern of recognition. Received: 5 June 1996 / Accepted after revision: 17 October 1996     

Black yeast symbionts compromise the efficiency of antibiotic defenses in fungus-growing ants

Multiplayer symbioses are common in nature, but our understanding of the ecological dynamics occurring in complex symbioses is limited. The tripartite mutualism between fungus-growing ants, their fungal cultivars, and antibiotic-producing bacteria exemplifies symbiotic complexity. Here we reveal how black yeasts, newly described symbionts of the ant-microbe system, compromise the efficiency of bacteria-derived antibiotic defense in fungus-growing ants. We found that symbiotic black yeasts acquire nutrients from the ants' bacterial mutualist, and suppress bacterial growth. Experimental manipulation of ant colonies and their symbionts shows that ants infected with black yeasts are significantly less effective at defending their fungus garden from Escovopsis, a prevalent and specialized pathogen. The reduction of mutualistic bacterial biomass on ants, likely caused by black yeast symbionts, apparently reduces the quantity of antibiotics available to inhibit the garden pathogen. Success of the ant-fungal mutualism is directly dependent on fungus garden health. Thus our finding that black yeasts compromise the ants' ability to deal with the garden parasite indicates that it is an integral component of the symbiosis. This is further evidence that a full understanding of symbiotic associations requires examining the direct and indirect interactions of symbionts in their ecological community context.     

Waste management in the leaf-cutting ant Acromyrmex echinatior: the role of worker size, age and plasticity

Division of labour is the hallmark of the success of many social animals. It may be especially important with regard to waste management because waste often contains pathogens or hazardous toxins and worker specialisation can reduce the number of group members exposed to it. Here we examine waste management in a fungus-farming, leaf-cutting ant, Acromyrmex echinatior, in which waste management is necessary to protect their vulnerable fungal crop. By marking ants with task-specific paint colours, we found clear division of labour between workers that engage in waste management and those that forage, at least during the fine timescale of the 3-day marking period. This division of labour was influenced by both age and size, with waste management workers tending to be smaller and younger than foragers. The role of preventing contaminated ants from entering the colony was fulfilled mainly by medium-sized workers. When the level of waste was experimentally increased, most of the ants that responded to remove the waste were workers previously engaged in tasks inside the nest rather than external waste workers or foragers. These responding workers tended to be young and medium-sized. Surprisingly, the responding ants were subsequently able to revert back to working within the fungus garden, but the probability of them doing so depended on their age and the length of time they were exposed to waste. The results demonstrate the importance of division of labour with regard to waste management in A. echinatior and show that this is adaptable to changing needs.     

Nest separation and the dynamics of the Gestalt odor in the polydomous ant Cataglyphis iberica (Hymenoptera, Formicidae)

In the polydomous ant species Cataglyphis iberica, nests belonging to the same colony are completely separated during hibernation. In order to examine whether this separation induces changes both in the hydrocarbon profile and in recognition ability between adult nestmates, we separated groups of workers for several months under two different conditions: at hibernation temperature and at room temperature. At room temperature, recognition remained unchanged but separation led to longer mutual antennations relative to non-separated controls. When half of a colony was placed under hibernation conditions, antennal interactions also increased in duration and a few aggressive interactions emerged between separated ants. This aggressiveness never reached the intercolonial level observed in this species. In both cases, the hydrocarbon profiles showed differences between individuals after separation while remaining homogeneous within each nest. This chemical modification may induce the longer antennations observed. After separated groups were reunited, individuals recovered their previous antennation pattern and a convergence in hydrocarbon profiles was again observed. These concurrent observations suggest that hydrocarbons are transferred between nestmates. In C. iberica, the formation of the colonial odor seems to follow the “Gestalt” model which allows all satellite nests of a colony to have a common colonial odor. In the field, temporary nest isolation during hibernation may induce divergence between satellites. The role of adult transport in connecting nests during the active season to obtain an efficient Gestalt odor is discussed. Received: 16 June 1997 / Accepted after revision: 25 October 1997     

Dufour gland secretion in the harvester ant genus <Emphasis Type="Italic">Pogonomyrmex</Emphasis>

Summary. Dufour gland secretions of the harvester ants Pogonomyrmex barbatus, P. rugosus and P. maricopa were investigated. The glandular blends exhibit species specific patterns, but more importantly, based on indiviual profiles of Dufour gland contents of colony members it is possible to separate the colonies from each other in each species. It is possible that these collective colony specific cues serve as longer lasting trunk route markers. Behavioral tests demonstrate that workers of P. rugosus prefer homing routes marked by members of their own colony to routes marked by a foreign conspecific colony.     

Kin discriminators in the eusocial sweat bee <Emphasis Type="Italic">Lasioglossum malachurum</Emphasis>: the reliability of cuticular and Dufour’s gland odours

The ability to discriminate degrees of relatedness may be expected to evolve if it allows unreciprocated altruism to be preferentially directed towards kin (Hamilton in J Theor Biol 7:1–16, 1964). We explored the possibility of kin recognition in the primitively eusocial halictid bee Lasioglossum malachurum by investigating the reliability of worker odour cues that can be perceived by workers to act as indicators of either nest membership or kinship. Cuticular and Dufour’s gland compounds varied significantly among colonies of L. malachurum, providing the potential for nestmate discrimination. A significant, though weak, negative correlation between chemical distance and genetic relatedness (r = −0.055, p < 0.001) suggests a genetic component to variation in cuticular bouquet, but odour cues were not informative enough to discriminate between different degrees of relatedness within nests. This pattern of variation was similar for Dufour’s gland bouquets. The presence of unrelated individuals within nests that are not chemically different from their nestmates suggests that the discrimination system of L. malachurum is prone to acceptance errors. Compounds produced by colony members are likely combined to generate a gestalt colony chemical signature such that all nestmates have a similar smell. The correlation between odour cues and nest membership was greater for perceived compounds than for non-perceived compounds, suggesting that variability in perceived compounds is a result of positive selection for nestmate recognition despite potentially stabilising selection to reduce variability in odour differences and thereby to reduce costs derived from excessive intracolony nepotistic behaviour.     

Construction of chimaeric gardens through fungal intercropping: a symbiont choice experiment in the leafcutter ant Atta texana (Attini, Formicidae)

Interspecies or intraspecies cooperation can be stabilized evolutionarily if choosing partners favor beneficial partners and discriminate against non-beneficial partners. We quantified such partner choice (symbiont choice) in the leafcutter ant Atta texana (Attini, Formicidae) by presenting the ants in a cafeteria-style preference assay with genotypically distinct fungal cultivars from A. texana and Acromyrmex versicolor. Symbiont choice was measured as the ants' tendency to choose one or more cultivar(s) from several pure (axenic) cultivar fragments and convert a given fungal fragment into a garden. Microsatellite DNA fingerprinting enabled us to identify the cultivars chosen by the ants for their gardens. In 91% of the choice tests, A. texana workers combined multiple cultivars into a single intercropped, chimaeric garden, and the cultivars coexisted in such chimaeric gardens for as long as 4 months. Coexistence of distinct fungal genotypes in chimaeric gardens appears to contradict a recent model of cultivar competition postulating that each cultivar secretes incompatibility compounds harming other cultivars, which presumably would preclude the intercropped polyculture observed in our experiments. Although we found no clear evidence of novel, recombinant genotypes in the experimental chimaeric gardens, the intercropping of cultivar genotypes may occasionally lead under natural conditions to exchange of genetic material between coexisting cultivars, thus introducing novel cultivar genotypes into the leafcutter symbiosis. Symbiont choice by ants and any competition between coexisting cultivar strains in chimaeric gardens do not appear to operate fast enough in our laboratory assay to convert chimaeric gardens into the monocultures observed for A. texana under natural conditions.     

Increased grooming after repeated brood care provides sanitary benefits in a clonal ant

Repeated pathogen exposure is a common threat in colonies of social insects, posing selection pressures on colony members to respond with improved disease-defense performance. We here tested whether experience gained by repeated tending of low-level fungus-exposed (Metarhizium robertsii) larvae may alter the performance of sanitary brood care in the clonal ant, Platythyrea punctata. We trained ants individually over nine consecutive trials to either sham-treated or fungus-exposed larvae. We then compared the larval grooming behavior of naive and trained ants and measured how effectively they removed infectious fungal conidiospores from the fungus-exposed larvae. We found that the ants changed the duration of larval grooming in response to both, larval treatment and their level of experience: (1) sham-treated larvae received longer grooming than the fungus-exposed larvae and (2) trained ants performed less self-grooming but longer larval grooming than naive ants, which was true for both, ants trained to fungus-exposed and also to sham-treated larvae. Ants that groomed the fungus-exposed larvae for longer periods removed a higher number of fungal conidiospores from the surface of the fungus-exposed larvae. As experienced ants performed longer larval grooming, they were more effective in fungal removal, thus making them better caretakers under pathogen attack of the colony. By studying this clonal ant, we can thus conclude that even in the absence of genetic variation between colony members, differences in experience levels of brood care may affect performance of sanitary brood care in social insects.     

Predatory behavior and chemical communication in two Metapone species (Hymenoptera:Formicidae)

Summary. Colonies of two species of Metapone (M. madagascarica, M. new species.) were collected in Madagascar and established in laboratory nests. It could be demonstrated that both species are specialist predators of termites (Cryptotermes kirbyi). During hunting the ants sting the termites and thereby paralyze and preserve the prey alive. In this way prey can be stored in the ant nest for extended periods. During foraging and colony emigrations the ants lay chemical trails with poison gland secretions. Among the seven compounds identified in the venom only methyl pyrrole-2-carboxylate elicits trail following behavior in both Metapone species. Received 11 February 2002, accepted 23 February 2002.     

Do these eggs smell funny to you?: an experimental study of egg discrimination by hosts of the social parasite Polyergus breviceps (Hymenoptera: Formicidae)

Social parasites exploit the behaviours of other social species. Infiltration of host systems involves a variety of mechanisms depending on the conditions within the host society and the needs of the social parasite. For many species of socially parasitic ants, colony establishment entails the usurpation of colonies of other species. This frequently involves the eviction or death of the host colony queen and the subsequent adoption of the invading queen. The social parasite queen achieves host worker acceptance by either manipulating the nest-mate recognition processes of the host or undergoing chemical modification. Little is known, however, about how host workers respond to social parasite eggs or whether host species defend against brood parasitism during parasite invasions. Host species are believed to adopt social parasite offspring because the recent common ancestry between many social parasites and their hosts may grant the sharing of certain characteristics such as chemical cues. Use of multiple host species, however, suggests other processes are needed for the social bond between host and parasite young to form. This study reports the findings of adoption bioassays in which eggs from a slave-maker ant, Polyergus breviceps, were offered to workers of two of its host species from unparasitised or newly parasitised nests to determine whether P. breviceps eggs generally elicit rearing behaviours from multiple host species. Comparisons of parasite egg survival until adulthood with conspecific egg survival reveal that workers of both host species, free-living or newly enslaved, do not typically accept slave-maker eggs. Both host species thus have sufficient discriminatory power to reject social parasite eggs although our hydrocarbon analysis indicates parasite eggs may be adapted to their local host species. Combined these results suggest that host rearing of P. breviceps eggs may reflect an evolutionary equilibrium that is maintained by probability and cost of recognition errors.Communicated by L. Sundström     

The red and the black: habituation and the dear-enemy phenomenon in two desert Pheidole ants

Many species of territorial animals are more aggressive toward strangers than neighbors, a pattern of aggression referred to as the ’dear-enemy phenomenon.’ In many cases, the mechanism by which neighbors are discriminated from strangers and the function of neighbor-stranger discrimination remain controversial. We investigated the spatial patterns of inter-colony aggression within and between two Pheidole species of seed-harvesting ants in the Mojave Desert of California by quantifying aggression between colonies in standardized staged encounters. We also tested whether the level of fighting between workers of two colonies is affected by previous exposure to each other. We show that neighbors (i.e., colonies less that 2.6 m away) of either species are treated less aggressively than more distant colonies and that habituation may be a mechanism by which this discrimination is achieved. The variation in aggression among spatially distant colonies also suggests that additional genetic or environmental factors are involved in recognition. The function of the dear-enemy phenomenon in these ant species may be related to the greater risk to the resources of a colony presented by strange workers than workers from a neighboring colony. Received: 18 November 1999 / Received in revised form: 3 April 2000 / Accepted: 3 May 2000     

The interplay between genetic and environmental effects on colony insularity in the clonal invasive little fire ant <Emphasis Type="Italic">Wasmannia auropunctata</Emphasis>

The little fire ant, Wasmannia auropunctata, constitutes one clonal supercolony throughout Israel, providing an opportunity to examine the effects of genotype versus environment on nestmate recognition. Intraspecific encounters among field-collected or among laboratory-maintained colonies were nonaggressive, but encounters between freshly collected and laboratory-maintained colonies were highly aggressive. Analyses of cuticular hydrocarbons revealed that freshly field-collected colonies had distinguishable profiles. Moreover, freshly collected colonies had profiles disparate from those of the same colonies after 4 months in the laboratory. These results indicate a strong interplay between genetic-based and environmentally based effects on the recognition cues. We propose that in the field the ants’ diet breadth is broad and consequently the incorporation of diet-borne substances is insufficient to mask the genetically determined cues. In the laboratory, however, the restricted diet promoted the incorporation of alien hydrocarbons at high levels, thus altering the genetically based cues to the point of alienation. These results shed a new light on the mechanisms by which environmental cues may affect label and/or template formation in ants. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.