Challenges and a call to action for protecting European red wood ants.

Red wood ants (RWAs) are a group of keystone species widespread in temperate and boreal forests of the Northern Hemisphere. Despite this, there is increasing evidence of local declines and extinctions. We reviewed the current protection status of RWAs throughout Europe and their International Union for the Conservation of Nature (IUCN) threat classification. Only some RWA species have been assessed at a global scale, and not all national red lists of the countries where RWAs are present include these species. Different assessment criteria, inventory approaches, and risk categories are used in different countries, and data deficiency is frequent. Legislative protection is even more complex, with some countries protecting RWAs implicitly together with the wildlife fauna and others explicitly protecting the whole group or particular species. This complexity often occurs within countries, for example, in Italy, where, outside of the Alps, only the introduced species are protected, whereas the native species, which are in decline, are not. Therefore, an international, coordinated framework is needed for the protection of RWAs. This first requires that the conservation target should be defined. Due to the similar morphology, complex taxonomy, and frequent hybridization, protecting the entire RWA group seems a more efficient strategy than protecting single species, although with a distinction between autochthonous and introduced species. Second, an update of the current distribution of RWA species is needed throughout Europe. Third, a protection law cannot be effective without the collaboration of forest managers, whose activity influences RWA habitat. Finally, RWA mounds offer a peculiar microhabitat, hosting a multitude of taxa, some of which are obligate myrmecophilous species on the IUCN Red List. Therefore, RWAs' role as umbrella species could facilitate their protection if they are considered not only as target species but also as providers of species-rich microhabitats.

Las hormigas rojas de la madera (HRM) conforman un grupo de especies clave con amplia distribución en los bosques templados y boreales del Hemisferio Norte. A pesar de lo anterior, cada vez hay más evidencia de su declinación y extinción local. Revisamos el estado actual de protección de las HRM en toda Europa y su clasificación en la Lista Roja de la Unión Internacional para la Conservación de la Naturaleza (UICN). Sólo se han evaluado algunas especies de HRM a escala mundial y no todas las listas rojas nacionales de los países con presencia de HRM incluyen a estas especies. Los diferentes países usan criterios de evaluación, estrategias de inventario y categorías de riesgo distintos, además de que la información deficiente es habitual. La protección legislativa es todavía más compleja pues algunos países protegen implícitamente a las HRM junto con la fauna silvestre y otros protegen explícitamente a todo el grupo o a una especie particular. Esta complejidad ocurre a menudo en los países (por ejemplo: Italia) en donde, fuera de los Alpes, sólo se protege a las especies introducidas, mientras a las especies nativas, que están declinando, no se les protege. Por lo tanto, se requiere un marco de trabajo internacional y coordinado para proteger a las HRM. Esto necesita primero que se defina el objetivo de conservación. Ya que las HRM tienen similitudes morfológicas, una taxonomía compleja e hibridación frecuente, la protección del grupo completo, con la distinción entre las especies autóctonas y las introducidas, parece ser una estrategia más eficiente que la protección de una sola especie. Segundo, se debe actualizar la distribución actual de las HRM en Europa. Tercero, una ley de protección no puede ser efectiva sin la colaboración de los gestores forestales, cuya actividad influye sobre el hábitat de las HRM Finalmente, los montículos de las HRM ofrecen un microhábitat peculiar pues hospedan a una multitud de taxones, algunos de los cuales son especies mirmecófilas obligadas presentes en la Lista Roja de la UICN. Así, el papel de las HRM como especie paraguas podría facilitar su protección si se les considera no sólo como especies diana sino también como proveedoras de microhábitats con riqueza de especies.

Toxicity of Tire Rubber Microplastics to Freshwater Sediment Organisms.

High emission of tire rubber particles to the surrounding environment is an inevitable consequence of the current habits of transportation. Although most of the emissions stay within a close range of the sources, it has been proven that the smallest particles can be transported to remote locations through the atmosphere, including inland water bodies. It has been estimated that a relevant portion of the global emissions of tire rubber particles reach surface waters, but effects on aquatic life in the receiving water bodies are not completely understood. In the present study, we used the freshwater sediment dwellers Lumbriculus variegatus and Chironomus riparius to examine the toxicity of tire rubber particles at environmentally relevant concentrations, using different types of sediment and two particle sizes of tire rubber. Overall, the experiments were unable to discern any effects on the growth, survival or reproduction of the two animals tested. Significant differences were found among the animals dwelling on different sediments, but the effects were not attributable to the presence of tire rubber particles. This study provides important information regarding the lack of effect of tire rubber particles in laboratory experiments with model sediment dwellers and opens more questions about the potential effects of tire rubber particles in the real environment with longer durations and varying environmental factors. The influence of other factors such as the leaching of additives in the overall toxicity of tire rubber particles should be also considered.

Benefits of insect colours: a review from social insect studies.

Insect colours assist in body protection, signalling, and physiological adaptations. Colours also convey multiple channels of information. These channels are valuable for species identification, distinguishing individual quality, and revealing ecological or evolutionary aspects of animals' life. During recent years, the emerging interest in colour research has been raised in social hymenopterans such as ants, wasps, and bees. These insects provide important ecosystem services and many of those are model research organisms. Here we review benefits that various colour types give to social insects, summarize practical applications, and highlight further directions. Ants might use colours principally for camouflage, however the evolutionary function of colour in ants needs more attention; in case of melanin colouration there is evidence for its interrelation with thermoregulation and pathogen resistance. Colours in wasps and bees have confirmed linkages to thermoregulation, which is increasingly important in face of global climate change. Besides wasps use colours for various types of signalling. Colour variations of well chemically defended social insects are the mimetic model for unprotected organisms. Despite recent progress in molecular identification of species, colour variations are still widely in use for species identification. Therefore, further studies on variability is encouraged. Being closely interconnected with physiological and biochemical processes, insect colouration is a great source for finding new ecological indicators and biomarkers. Due to novel digital imaging techniques, software, and artificial intelligence there are emerging possibilities for new advances in this topic. Further colour research in social insects should consider specific features of sociality.

Independent and interactive effects of immune activation and larval diet on adult immune function, growth and development in the greater wax moth (Galleria mellonella).

Organisms in the wild are likely to face multiple immune challenges as well as additional ecological stressors, yet their interactive effects on immune function are poorly understood. Insects are found to respond to cues of increased infection risk by enhancing their immune capacity. However, such adaptive plasticity in immune function may be limited by physiological and environmental constraints. Here, we investigated the effects of two environmental stressors - poor larval diet and an artificial parasite-like immune challenge at the pupal stage - on adult immune function, growth and development in the greater wax moth (Galleria mellonella). Males whose immune system was activated with an artificial parasite-like immune challenge had weaker immune response - measured as strength of encapsulation response - as adults compared to the control groups, but only when reared on high-nutrition larval diet. Immune activation did not negatively affect adult immune response in males reared on low-nutrition larval diet, indicating that poor larval diet improved the capacity of the insects to respond to repeated immune challenges. Low-nutrition larval diet also had a positive independent effect on immune capacity in females, yet it negatively affected development time and adult body mass in both sexes. As in the nature immune challenges are rarely isolated, and adverse nutritional environment may indicate an elevated risk of infection, resilience to repeated immune challenges as a response to poor nutritional conditions could provide a significant fitness advantage. This study highlights the importance of considering environmental context when investigating the effects of immune activation in insects.

Effects of overwintering temperature on the survival of the black garden ant (Lasius niger).

The overwintering temperatures of ants might well be elevated due to climate change. We studied whether the overwintering temperature affects the survival of the queens and whole colonies of the black garden ant, Lasius niger (Linnaeus, 1758). In two consecutive years (2009, 2010) we collected mated, colony founding queens (n = 280) from the urban area of Turku, Finland. Half of the queens overwintered in +7 to +8 °C and the other half in +2 °C. After the overwintering period, we determined their survival rate and measured the body fat content, body size and immune defence (encapsulation rate) of overwintering queens. Using the same setup, we studied the survival of 1-year-old L. niger colonies (queen & workers). Overwintering at a lower temperature (+2 °C) decreased the survival of workers. The survival of colony founding queens differed between years, but unlike with workers, the overwintering temperature did not affect their survival: neither in the colony experiment nor in the single queen experiment. All of the surviving queens managed to produce their worker offspring at the same rate. The relative amount of body fat of queens was higher for those who overwintered at a lower temperature, which is likely a result of lower energy consumption. We did not detect differences in the encapsulation rate between the temperature treatment groups. The ability of colony founding queens to tolerate wide overwintering temperature variations present in urban environments may explain the success of the colony in urban areas. As the colony grows, the overwintering chambers may extend more deeply into the ground. Thus, workers may not have to cope with such cold conditions as colony founding queens.

Similarity of body size in queens of the wood ant Formica aquilonia from optimal and sub-optimal habitats indicates a strong heritable component.

Body size in animals is affected by both genes and the environment (e.g., the amount of food resources). In ants, body size is related to several traits in an individual's physiology and life history. For example, a large queen may increase offspring production, thus increasing her overall fitness. In this study, whether sub-optimal environmental conditions affect the body size of queens of the red wood ant, Formica aquilonia Yarrow (Hymenoptera: Formicidae). The sizes (head width in mm) of virgin queens, i.e., gynes, originating from forest interiors (resource rich) and from commercial forest clear-cuts (resource poor) were measured. No differences in the body size of the queens from the two habitats were found. In addition, the within-nest variation in queen size was similar between habitat types. The results indicate that the body size variation of F. aquilonia queens is not sensitive to environmental variation, unlike F. aquilonia workers. The lack of environmental variation in queen size in F. aquilonia may be due to a strong selection in the past to monomorphic size in this obligately polygynous (multi-queened) species.

Transfer of elements into boreal forest ants at a former uranium mining site.

Ants can influence ecological processes, such as the transfer of elements or radionuclides, in several ways. For example, they redistribute materials while foraging and maintaining their nests and have an important role in terrestrial food webs. Quantitative data of the transfer of elements into ants is needed, e.g., for developing improved radioecological models. In this study, samples of red wood ants (genus Formica), nest material, litter and soil were collected from a former uranium mining site in Eastern Finland. Concentrations of 33 elements were analyzed by Inductively Coupled Plasma-Mass Spectroscopy/Optical Emission Spectroscopy. Estimated element concentrations in spruce needles were used as a proxy for studying the transfer of elements into ants via aphids because spruces host the most important aphid farms in boreal forests. Empirically determined organism/medium concentration ratios (CRs) are commonly used in radioecological models. Ant/soil CRs were calculated and the validity of the fundamental assumption behind the of use of CRs (linear transfer) was evaluated. Elements that accumulated in ants in comparison to other compartments were cadmium, potassium, phosphorus, sulfur, and zinc. Ant uranium concentrations were low in comparison to soil, litter, or nest material but slightly elevated in comparison to spruce needles. Ant element concentrations were quite constant regardless of the soil concentrations. Non-linear transfer models could therefore describe the soil-to-ant transfer better than conventional CRs.

Phenotypic Plasticity of Common Wasps in an Industrially Polluted Environment in Southwestern Finland.

Insects vary in the degree of their adaptability to environmental contamination. Determining the responses with phenotypic plasticity in ecologically important species in polluted environments will ease further conservation and control actions. Here, we investigated morphological characteristics such as body size, body mass, and color of the common wasp Vespula vulgaris in an industrially polluted environment, considering different levels of metal pollution, and we studied the localization of contaminants in the guts of wasps. We revealed some differences in morphological characteristics and melanization of wasps collected in habitats with high, moderate, and low levels of pollution. The results indicated that V. vulgaris from highly polluted environments had reduced melanin pigmentation on the face but increased melanin pigmentation on the 2nd tergite of the abdomen. In addition, with transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX), we found metal particles from the midgut of wasps originating from the polluted environment. Most of the particles were encapsulated with melanin pigment. This finding confirmed that in wasps, ingested metal particles are accumulated in guts and covered by melanin layers. Our data suggest that wasps can tolerate metal contamination but respond phenotypically with modification of their size, coloration, and probably with the directions of the melanin investments (immunity or coloration). Thus, in industrially polluted areas, wasps might probably survive by engaging phenotypic plasticity with no significant or visible impact on the population.

Altered gene expression in Chironomus riparius (insecta) in response to tire rubber and polystyrene microplastics.

The extent until which plastics are present in our surrounding environment completely exceeds our expectations. Plastic materials in the form of microplastics have been found in terrestrial, freshwater and marine environments and are transported through the atmosphere even to remote locations. However, we are still far from understanding the effects that they may have caused and are causing to biota. In the present study, we investigated the alterations in the expression of twelve genes in the aquatic insect Chironomus riparius after 36 h exposures to polystyrene and tire rubber microplastics at nominal concentrations of 1 and 10 mg L-1. The results indicated that several genes encoding for heat shock proteins (hsp90, Glycoprotein 93 (Gp93), hsc70, hsp60, hsp40, and the small HSP hsp17) were overexpressed respect to the control. In addition, the genes coding for manganese superoxide dismutase (SOD Mn, related to alleviation of oxidative stress) and for the FK506-binding protein of 39 kDa. (FKBP39, related to development and pupation) showed altered expression. Most of the alterations on gene expression level occurred at a concentration of 10 mg L-1 of tire rubber microplastics, although specific modifications arose at other concentrations of both rubber and polystyrene. On the contrary, one hsp gene (hsp10) and genes related to biotransformation and detoxification (Cyp9f2, Cyp12a2, and ABCB6) did not alter their expression in any of the treatments. Overall, the results of the gene expression indicated that microplastics (especially tire rubber) or their additives caused cellular stress that led to some alterations in the normal gene expression but did not cause any mortality after 36 h. These results highlight the need for more studies that describe the alterations caused by microplastics at the molecular level. Additionally, it opens questions about the effects caused to aquatic fauna in environmental realistic situations, especially in hot spots of microplastic contamination (e.g., tire rubber released in storm water runoff discharge points).

Transfer of elements relevant to radioactive waste into chironomids and fish in boreal freshwater bodies.

Information on transfer of elements and their radionuclides is essential for radioecological modeling. In the present study, we investigated the transfer of Cl, Co, Mo, Ni, Se, Sr, U and Zn in a boreal freshwater food chain. These elements were selected on the basis that they have important radionuclides that might be released into the biosphere from various stages of the nuclear fuel cycle. Water, sediment, chironomid larvae (Chironomus sp.), roach (Rutilus rutilus) and perch (Perca fluviatilis) were sampled from two ponds near a former uranium mine and one reference pond located further away from the mining area. Concentrations measured in water, sediment and the three animal species indicated the importance of sediment as a source of uptake for most of the elements (but not Cl). This should be considered in radioecological models, which conventionally predict concentration in aquatic organisms from concentration in water. The results also show that the assumption of linear transfer (constant concentration ratio) may not be valid for elements into fish. The results of this study show that further basic research is needed to understand the fundamental processes involved in transfer of elements into freshwater organisms in order to develop radioecological models.

Facing the threat: common yellowjacket wasps as indicators of heavy metal pollution.

We investigated the common wasp, Vespula vulgaris as a bioindicator and biomonitor of metals in the industrial area. Using traps, we collected 257 yellowjackets along a pollution gradient in the Harjavalta Cu-Ni smelter in Southwest Finland. Our method detected metal elements such as arsenic (As), cobalt (Co), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), zinc (Zn), and mercury (Hg) in wasps. The data analyses revealed V. vulgaris can be a proper indicator for As, Cd, Co, Cu, Ni, and Pb, rather than for Fe and Zn contamination. Body burdens of As, Cd, Co, Cu, Ni, and Pb decreased with an increase in distance from smelter. Enrichment factor (EF) followed the pattern Pb ˃ Cd ˃ As ˃ Co ˃ Cu ˃ Ni. The highest bioaccumulation (BAF) values were revealed for Cd (5.9) and the lowest for Pb (0.1). Specially designed software (WaspFacer) allowed revealing body burdens of As, Cd, Co, Cu, Ni, and Pb to be associated with rather smaller than more asymmetric facial colour markings in yellowjackets. These results add to the body of literature on how heavy metal contaminants can have tangible phenotypic effects on insects and open future opportunities for using wasps as indicators of metal pollution.

Bird Feces as Indicators of Metal Pollution: Pitfalls and Solutions.

Bird feces are commonly used as a proxy for measuring dietary metal exposure levels in wild populations. Our study aims to improve the reliability and repeatability of fecal metal measurements and gives some recommendations for sampling. First, we studied levels of variation in metallic element (arsenic, calcium, cadmium, cobalt, copper, nickel, lead) concentrations: temporal variation within an individual, among siblings in a brood and among-brood/spatial variation. Second, we explored the variation caused by dual composition (urate vs. feces) of bird droppings. Two sets of fresh fecal samples were collected from pied flycatcher (Ficedula hypoleuca) nestlings living in a metal polluted area in summers 2017 (dataset 1) and 2018 (dataset 2). We found a great deal of temporal intra-individual variation in metal levels, suggesting that dietary exposure varied markedly in a short time scale (within a day). A sample from only one nestling per brood did not well describe the brood mean value, and we recommend that at least four siblings should be sampled. Brood level samples give relatively good temporal repeatability for most metals. For all the metals, the levels in the fecal portion were more than double to those in the urate portion. Since the mass proportion of urate in the bird droppings varied a great deal among samples, standardizing sampling, e.g., by collecting only the fecal part, would markedly reduce the variation due to composition. Alternatively, urate portion could be used for biomonitoring of internally circulated bioavailable metal.

Is developmental instability in chironomids a sensitive endpoint for testing uranium mine-affected sediments?

There is increasing interest in effects of radionuclides on non-human species, but methods for studying such effects are not well developed. The aims of the current study were to investigate the effects of uranium mine-affected sediments on non-biting midge Chironomus riparius and to compare sensitivity of different endpoints. The midge larvae were exposed in controlled laboratory conditions to sediments from two ponds downstream from an abandoned uranium mine and a reference pond not receiving water from the mining site. Quartz sand was used as an additional control. Developmental effects were assessed by evaluating emergence of adult midges, body mass, and fluctuating asymmetry (FA) in the length of wing upper vein. FA has been suggested to be a sensitive indicator of developmental instability, but the results of previous studies are inconsistent. In the present study, no difference in FA was observed between the treatment groups, but time to emergence was significantly delayed in the contaminated sediments. The approach used in this study (laboratory experiments with sediments from a contaminated site) avoids confounding due to uncontrolled environmental variables and adaptation to long-term contamination, which may mask effects on natural populations. Using this approach, we found no effects on FA of wing length. Time to emergence, in contrast, was found to be a more sensitive endpoint.

Brood parasitism in eusocial insects (Hymenoptera): role of host geographical range size and phylogeny.

Interspecific brood parasitism is common in many animal systems. Brood parasites enter the nests of other species and divert host resources for producing their own offspring, which can lead to strong antagonistic parasite-host coevolution. Here, we look at commonalities among social insect species that are victims of brood parasites, and use phylogenetic data and information on geographical range size to predict which species are most probably to fall victims to brood parasites in the future. In our analyses, we focus on three eusocial hymenopteran groups and their brood parasites: (i) bumblebees, (ii) Myrmica ants, and (iii) vespine and polistine wasps. In these groups, some, but not all, species are parasitized by obligate workerless inquilines that only produce reproductive-caste descendants. We find phylogenetic signals for geographical range size and the presence of parasites in bumblebees, but not in ants and wasps. Phylogenetic logistic regressions indicate that the probability of being attacked by one or more brood parasite species increases with the size of the geographical range in bumblebees, but the effect is statistically only marginally significant in ants. However, non-phylogenetic logistic regressions suggest that bumblebee species with the largest geographical range sizes may have a lower likelihood of harbouring social parasites than do hosts with medium-sized ranges. Our results provide new insights into the ecology and evolution of host-social parasite systems, and indicate that host phylogeny and geographical range size can be used to predict threats posed by social parasites, as well to design efficient conservation measures for both hosts and their parasites. This article is part of the theme issue 'The coevolutionary biology of brood parasitism: from mechanism to pattern'.

Control of Dust Dispersion From an Enclosed Renovation Site Into Adjacent Areas by Using Local Exhaust Ventilation.

OBJECTIVE: In real-world applications, implementation of an enclosure and negative pressurization is not always adequate to prevent the dispersion of dust from renovation sites. This study aimed to quantify the effect of local exhaust ventilation (LEV) in controlling the dust concentration within an enclosed renovation site to reduce the dust dispersion into adjacent areas. METHODS: The concentrations of inhalable and respirable dust were measured in 16 cases during renovation projects. Filter samples and time-resolved dust concentration data were collected simultaneously from the renovation site and adjacent areas to assess the efficacy of LEV in limiting the dust dispersion. RESULTS: The dispersion of dust outside of the enclosed renovation sites was limited significantly with using LEV. The estimated dust removal efficiency of LEV was 79% for inhalable dust concentration in the renovation site and 62% in the adjacent area. The use of LEV reduced the concentration of respirable dust by 33‒90% in the adjacent area and 80-87% within the renovation site. CONCLUSIONS: Using LEV was found to play a substantial role in dust containment, particularly when the enclosure failed to maintain the negative pressure. The study provides data-driven recommendations that are of practical importance as they promote healthier workplaces and policy improvements. In conclusion, dust dispersion into adjacent areas is prevented with an airtight enclosure (including airlocks) and continuous negative pressure. Dust containment was also obtained by having target dust concentration at the enclosed renovation site to below 4 mg m-3 for inhalable dust and below 1 mg m-3 for respirable dust, even though the enclosures not being continuously under negative pressure. The suggested target concentrations are achievable by using on-tool LEV during the most dust-producing tasks.

Immune defense of ants is associated with changes in habitat characteristics.

Although the immune functions of insects are known to correlate with body condition and food resources, the association between habitat structure and immune function is still largely unknown. We studied the effects of forest clear-cutting on encapsulation rate in gynes and workers in the forest-dwelling ant Formica aquilonia. Forest logging resulted in disturbed immunity in workers and gynes. Logging enhanced encapsulation reaction in gynes, whereas decreased that of workers. In gynes, there was a likely trade-off between growth and immune function that was apparent in terms of different investment in size and immune function in different habitats. In workers, however, such associations were not found. The results indicate that, because of disturbed immunity, environmental stress may increase susceptibility of wood ants to diseases and parasites in disturbed habitats.

Ants and their nests as indicators for industrial heavy metal contamination.

Ants accumulate heavy metals and respond to pollution with modification in species composition, community structure, altered behaviour and immunity. However, the levels of heavy metals in ants' nests and explicit individual-level responses towards heavy metals have not been revealed. We found that red wood ants Formica lugubris accumulate high and correlated values of such heavy metals as Al, Cd, Co, Cu, Fe, Ni, Pb and Zn both in ants and nest material near cobalt smelter in Finland. Relative differences in metal concentrations were higher in nests than in ants. The highest values were obtained for elements such as Co (36.6), Zn (14.9), Cd (9.7), Pb (8.5), Cu (7.4), Ni (6.4), As (4.7), Cr (2.9) and Fe (2.4) in nest material, and Co (32.7), Cd (6.3), Pb (6), Fe (2.8), Ni (2.9) and Zn (2.1) in ants. In industrial and reference areas, ants have no differences in size, but differed in dry and residual body mass. In polluted areas, F. lugubris had less melanised heads, but not thoraxes. The sensitivity of cuticular colouration in red wood ants subjected to heavy metal pollution might be related to metal-binding properties of melanins. The overall results are useful for the improvement of biomonitoring techniques using ants as indicators of industrial contamination and for further discovery of novel ecotoxicological biomarkers.

Genetic analysis reveals Finnish Formica fennica populations do not form a separate genetic entity from F. exsecta.

Coptoformica Müller, 1923 is a subgenus of Formica Linnaeus, 1758 that consists of c. a dozen species of ants that typically inhabit open grassy habitats and build small nest mounds. The most recent addition to the group is Formica fennica Seifert, 2000. The description was based on morphological characters, but the species status has not been confirmed by molecular methods. In this study, we use thirteen DNA microsatellite markers and a partial mitochondrial COI gene sequence to assess the species status of F. fennica, by comparing the genetic variation among samples identified as F. fennica and six other boreal Formica (Coptoformica) species. Most of the species studied form separate, discontinuous clusters in phylogenetic and spatial analyses with only little intraspecific genetic variation. However, both nuclear and mitochondrial markers fail to separate the species pair F. exsecta Nylander, 1846 and F. fennica despite established morphological differences. The genetic variation within the F. exsecta/fennica group is extensive, but reflects spatial rather than morphological differences. Finnish F. fennica populations studied so far should not be considered a separate species, but merely a morph of F. exsecta.

Heavy metal pollution disturbs immune response in wild ant populations.

Concern about the effects of environmental contaminants on immune function in both humans and wildlife is growing and practically nothing is known about this impact on terrestrial invertebrates, even though they are known to easily accumulate pollutants. We studied the effect of industrial heavy metal contamination on immune defense of a free-living wood ant (Formica aquilonia). To find out whether ants show an adapted immune function in a polluted environment, we compared encapsulation responses between local and translocated colonies. Local colonies showed higher heavy metal levels than the translocated ones but the encapsulation response was similar between the two groups, indicating that the immune system of local ants has not adapted to high contamination level. The encapsulation response was elevated in moderate whereas suppressed in high heavy metal levels suggesting higher risk for infections in heavily polluted areas.