Development of parasitic <Emphasis Type="Italic">Maculinea teleius</Emphasis> (Lepidoptera,Lycaenidae) larvae in laboratory nests of four <Emphasis Type="Italic">Myrmica</Emphasis> ant host species

Maculinea butterflies are social parasites of Myrmica ants. Methods to study the strength of host ant specificity in the Maculinea–Myrmica association include research on chemical and acoustic mimicry as well as experiments on ant adoption and rearing behaviour of Maculinea larvae. Here we present results of laboratory experiments on adoption, survival, development and integration of M. teleius larvae within the nests of different Myrmica host species, with the objective of quantifying the degree of specialization of this Maculinea species. In the laboratory, a total of 94 nests of four Myrmica species: M. scabrinodis, M. rubra, M. ruginodis and M. rugulosa were used. Nests of M. rubra and M. rugulosa adopted M. teleius larvae more readily and quickly than M. ruginodis colonies. No significant differences were found in the survival rates of M. teleius larvae reared by different ant species. Early larval growth of M. teleius larvae differed slightly among nests of four Myrmica host species. Larvae reared by colonies of M. rugulosa which were the heaviest at the beginning of larval development had the lowest mean larval body mass after 18 weeks compared to those reared by other Myrmica species. None of the M. teleius larvae was carried by M. scabrinodis or M. rubra workers after ant nests were destroyed, which suggests a lack of integration with host colonies. Results indicate that Myrmica species coming from the same site differ in their ability to adopt and rear M. teleius larvae but there was no obvious adaptation of this butterfly species to one of the host ant species. This may explain why, under natural conditions, all four ants can be used as hosts of this butterfly species. Slight advantages of particular Myrmica species as hosts at certain points in butterfly larval development can be explained by the ant species biology and colony structure rather than by specialization of M. teleius.     

A mowing experiment to evaluate the influence of management on the activity of host ants of <Emphasis Type="Italic">Maculinea</Emphasis> butterflies

Maculinea butterflies obligatory parasitize certain species of Myrmica ants. Thus, the presence of the host ant species is a limiting factor for the survival of a Maculinea population. Here, we analyse the influence of vegetation structure and ground temperature on ant diversity and abundance on Maculinea habitats, with the final aim of identifying the environmental variables determining patterns of variation in species composition in order to recommend a mowing regime that will promote our three target species: Maculinea teleius, M. nausithous and M. alcon. Experimental plots with different mowing regimes were established at eight sites in South-Eastern Germany, a region which still contains a number of relatively large, stable populations of these threatened butterfly species. Among the seven different ant species recorded, four belong to the genus Myrmica (M. scabrinodis, M. rubra, M. ruginodis and M. vandeli). Among these, M. scabrinodis results most abundant at all sites. In a CCA analysis of environmental variables recorded at the studied plots, ant species diversity appears largely determined by litter cover, mean temperature, and mean grass cover. Mowing once a year, in the second half of September, after the larvae have left their host plants, enhances the abundance of Myrmica ants in the meadows, and would be the best management compromise for all three species.     

Patterns of host ant use by sympatric populations of <Emphasis Type="Italic">Maculinea alcon</Emphasis> and <Emphasis Type="Italic">M. ‘rebeli’</Emphasis> in the Carpathian Basin

Maculinea butterflies show social parasitism via obligatory myrmecophily as their larvae are adopted and raised to pupation by Myrmica ants. Suitable hosts differ for different Maculinea species, and host ant specificity can further differ at the population-level. Although early studies suggested single ant species as main hosts for each Maculinea species, it has recently become clear that their host ant specificity is more complex. Maculinea alcon and Maculinea ‘rebeli’ have variously been separated according to adult and larval morphology, phenology, and their use of different ecosystems, including host plant and host ant species. However, recent genetic evidence has questioned their separation as good species. Here we compare the use of host ants by M. alcon and M. ‘rebeli’ at the regional scale in NE-Hungary and Transylvania (Romania), where molecular studies have found no species-level separation between the two forms. We opened 778 nests of Myrmica ants and searched for Maculinea specimens (larvae, pupae and exuviae) shortly before imago emergence from the nest in seven M. alcon sites, six M. ‘rebeli’- sites and one site where both M. alcon and M. ‘rebeli’ are syntopic. In all, Maculinea caterpillars were found in the nests of seven different ant species (M. alcon was recorded mainly with Myrmica scabrinodis and occasionally with M. salina and M. vandeli; M. ‘rebeli’ used mainly M. scabrinodis, M. sabuleti and M. schencki and occasionally M. lonae and M. specioides). Myrmica scabrinodis was found to be a general host of both M. alcon and M. ‘rebeli’, which is the first record for a common host ant of these two closely related butterflies within the same region. However there were also differences in host ant use patterns between the sites occupied by the two Maculinea taxa, which reflect differences in Myrmica communities between the two types of habitat. Possible explanations for the similar but not identical host use patterns of M. alcon and M. ‘rebeli’, and their relevance for the question of whether they are separate species are discussed. Received 27 November 2007; revised 28 May 2008; accepted 11 June 2008.     

Host specificity among Maculinea butterflies in Myrmica ant nests

Summary Ecological studies have been made of all 5 European species of Maculinea. These confirm that M. nausithous and M. rebeli live underground in Myrmica ant nests for 10 months of the year, as has long been known for the other 3 species. The main discovery was that each Maculinea species depends on a single, and different, host species of Myrmica. This specificity contradicts previous papers and scientific reviews of the relationship between Maculinea and ants. Therefore, early records are re-examined and 3 reasons are given to explain why most are misleading when applied to wild populations. Dependence on a single, rather than any, species of Myrmica explains why Maculinea populations exist in only a small minority of biotopes where their foodplants and Myrmica ants abound. It also explains the puzzling disappearance of Maculinea populations from apparently suitable sites. The discovery that M. alcon and M. rebeli depend on separate species of Myrmica that are not even closely related strengthens the argument that these butterflies are good species.     

Polymorphic growth in larvae of Maculinea butterflies, as an example of biennialism in myrmecophilous insects

The presence of annual and biennial individuals within the same population has been recently demonstrated in the myrmecophilous butterflies Maculinea rebeli and Maculinea alcon, which present a cuckoo strategy inside Myrmica nests, and Maculinea arion which is a predatory species. Here, we present field and laboratory data on polymorphic larval growth in two other predatory species of Maculinea: M. teleius and M. nausithous. Body mass distributions of pre-pupation larvae were bimodal in both species. These results point to the existence of larvae that develop in 1 or 2 years. We also showed that the probability of pupation depended on larval body mass. In the case of M. teleius, the critical body mass at which larvae have a 50% probability of pupation is about 80 mg. We suggest that polymorphism in Maculinea may have evolved as an adaptation to life in ant nests, a habitat which protects them from predators and provides food. However, the quality of this resource is highly variable and unpredictable. According to the bet-hedging hypothesis, if the habitat is unpredictable, females should have an advantage by producing more variable offspring. In the case of Maculinea butterflies, this may involve maintaining larvae that develop in 1 or 2 years.     

Interspecific differences in cuticular hydrocarbon profiles of Myrmica ants are sufficiently consistent to explain host specificity by Maculinea (large blue) butterflies

The chemical signatures on the cuticles of five common Myrmica ant species were analysed (49 colonies of M. rubra, M. ruginodis, M. sabuleti, M. scabrinodis and M. schencki), each ant being the specific host of one of the five threatened European species of Maculinea butterfly. The cuticular hydrocarbon profile (based on the relative abundance of each chemical) of each ant species was highly distinctive, even between the morphologically similar species M. sabuleti and M. scabrinodis. There was no significant difference in the chemical profiles of workers and larvae from any colony. Nor was there much pattern in the intraspecific variation: colonies from the same populations were significantly, but only slightly, more similar to each other than to colonies from distant populations. M. rubra showed remarkably little variation between populations sampled widely from northern Russia, Ukraine, Scotland and southern England. The data were compared with published profiles of M. rubra and two North American Myrmica species, and with a quantitative reanalysis of data for Maculinea rebeli caterpillars. We conclude that the hydrocarbon profiles of Myrmica species are sufficiently and consistently different for chemical mimicry to explain the pattern of host specificity recorded for the European Maculinea butterflies. The optimum strategy for chemical mimicry in each of the two life-styles of Maculinea larvae is discussed: we suggest that predatory species might benefit from mimicking the median profile of their model whereas the "cuckoo" species would benefit when variation between siblings encompasses a large range of the variation recorded within a local population of the model species.     

Chemical mimicry and host specificity in the butterfly Maculinea rebeli,a social parasite of Myrmica ant colonies

Although it has always been assumed that chemical mimicry and camouflage play a major role in the penetration of ant societies by social parasites, this paper provides the first direct evidence for such a mechanism between the larvae of the parasitic butterfly Maculinea rebeli and its ant host Myrmica schencki. In the wild, freshly moulted fourth-instar caterpillars, which have no previous contact with ants, appear to be recognized as ant larvae by foraging Myrmica workers, which return them to their nest brood chambers. Three hypotheses concerning the mechanism controlling this behaviour were tested: (i) the caterpillars produce surface chemicals that allow them to be treated as ant larvae; (ii) mimetic compounds would include hydrocarbons similar to those employed by Myrmica to recognize conspecifics and brood; and (iii) the caterpillars'' secretions would more closely mimic the profile of their main host in the wild, M. schencki, than that of other species of Myrmica. Results of behavioural bioassays and chemical analyses confirmed all three hypotheses, and explained the high degree of host specificity found in this type of highly specialized myrmecophile. Furthermore, although caterpillars biosynthesized many of the recognition pheromones of their host species (chemical mimicry), they later acquired additional hydrocarbons within the ant nest (chemical camouflage), making them near-perfect mimics of their individual host colony''s odour.     

Larval niche selection and evening exposure enhance adoption of a predacious social parasite, Maculinea arion (large blue butterfly), by Myrmica ants

Larvae of the butterfly genus Maculinea feed briefly on a foodplant before being adopted as social parasites into Myrmica ant nests. Each Maculinea species typically survives only with a single Myrmica species, yet the eggs are laid across the overlapping territories of 3-5 Myrmica species and several other ants. The ability of Maculinea arion - a 'predatory' species of Maculinea - to influence its adoption into host Myrmica colonies was studied for the first time in the field. Some earlier reports, involving captive non-host ants, suggested that larvae of the predatory Maculinea follow ant trails into host nests or wander some distance from their foodplant before being discovered and (after a long interaction) carried away by Myrmica foragers. No dispersal from foodplants occurred in wild Maculinea arion larvae. Instead, they increased by >100-fold their probability of being discovered and adopted by Myrmica spp., rather than by ants of other genera, by exposing themselves in the micro-niche occupied by Myrmica foragers at their time of day of peak foraging. Despite a complex, hour-long interaction with Myrmica workers before being carried to the nest, Maculinea arion did not enhance its adoption by host species of Myrmica. Eggs were laid without bias in Myrmica sabuleti (host) and Myrmica scabrinodis (non-host) territories; larval survival on Thymus was the same in both ants' territories; larvae waited to be found beneath their foodplant rather than seek their host; Myrmica sabuleti and Myrmica scabrinodis foraged in the same vertical and temporal niches, and had the same probability of discovering larvae; both ants behaved identically after finding larvae and took the same time to adopt them; and the ratio of wild larvae taken into Myrmica sabuleti or Myrmica scabrinodis nests was the same as the distribution between these ants of Thymus, eggs and pre-adoption larvae.     

Consequences of the arms race between <Emphasis Type="Italic">Maculinea teleius</Emphasis> social parasite and <Emphasis Type="Italic">Myrmica</Emphasis> host ants for myrmecophilous butterfly conservation

The arms race between Maculinea butterflies and Myrmica host ants leads to local host-parasite adaptations. In our study, we assessed whether sympatric and allopatric Myrmica scabrinodis populations exhibit behavioural differences towards Maculinea teleius larvae during the adoption-period when butterfly larvae need to be taken inside the Myrmica nest. The second aim was to assess the butterfly survival rate inside ant colonies from different populations. We used one sympatric host population and three allopatric populations: one infested by M. teleius and two uninfested populations. We found that ants from the sympatric population showed a higher number of positive behaviours toward M. teleius larvae during adoption than ants from the allopatric populations. There were no differences in the number of inspection or negative behaviour events. The survival of butterfly larvae was highest inside sympatric host colonies and differed from the survival of M. teleius reared by ants from the allopatric, uninfested populations. No difference was found for the survival rate of M. teleius raised by infested, allopatric host colonies compared to sympatric host populations. Our results suggest the lack of behavioural counter-adaptations of local hosts of M. teleius that more easily adopt and rear butterfly caterpillars compared to naive M. scabrinodis colonies. Our results may also have implications for Maculinea butterfly conservation, especially for reintroduction programmes. We suggest that the existence of behavioural host defences should be checked for the source host population, as well as for the Myrmica population from the reintroduction site. It may also be reasonable to introduce several Myrmica host colonies from the source butterfly host population.     

Choice behaviour of Myrmica rubra workers between ant larvae and larvae of their Phengaris (Maculinea) nausithous nest parasites

Larvae of Phengaris (Maculinea) butterflies are adopted by Myrmica workers and are obligate myrmecophiles. Brood recognition by Myrmica rubra workers was tested for concolonial larvae (M. rubra) versus allocolonial larvae (M. rubra and P. nausithous) to assay the mimetic efficiency of P. nausithous. In addition, we tested M. rubra ant colonies from different populations with and without the presence of Phengaris, to test for potential local adaptation in adoption behaviour. We show that M. rubra can distinguish between nest-mate and foreign larvae as well as between P. nausithous and their own larvae. Workers from the allopatric population inspected and rejected more P. nausithous larvae than workers from the sympatric population. This might reflect a local host adaptation in which the social parasite more efficiently mimes its sympatric host ants than allopatric ones.     

Interspecific relationships in co‐occurring populations of social parasites and their host ants

Myrmica ant colonies host numerous insect species, including the larvae of Maculinea butterflies and Microdon myrmicae hoverflies. Little is known about the interspecific relationships among these social parasites and their host ants occurring in sympatric populations. We investigated communities of social parasites to assess the strategies allowing them to share the same pool of resources (i.e. Myrmica colonies). The present study was carried out at five sites inhabited by different social parasite communities, each comprising varying proportions of Maculinea teleius, Maculinea nausithous, Maculinea alcon, and Microdon myrmicae. We investigated their spatial distributions, host segregation, the degree of chemical similarity between social parasites and hosts, and temporal overlaps in colony resource exploitation. Spatial segregation among social parasites was found in two populations and it arises from microhabitat preferences and biological interactions. Local conditions can drive selection on one social parasite to use a Myrmica host species that is not exploited by other social parasites. Myrmica scabrinodis and Myrmica rubra nests infested by larvae of two social parasite species were found and the most common co‐occurrence was between Ma. teleius and Mi. myrmicae. The successful coexistence of these two species derives from their exploitation of the host colony resources at different times of the year. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 699–709.     

<Emphasis Type="Italic">Myrmica</Emphasis> host-ants limit the density of the ant-predatory large blue <Emphasis Type="Italic">Maculinea nausithous</Emphasis>

Butterflies of the highly endangered genus Maculinea are parasites of red Myrmica ants. Prior to the adoption by Myrmica worker ants Maculinea caterpillars feed on a specific host plant. This field study aims to answer the question whether the density and distribution of the host plant Sanguisorba officinalis or the density of the host ant M. rubra limit the density of M. nausithous egg, larval and adult stage. We found that the density of M. nausithous egg stage and adult stage increased with the density of the host ant. The density of M. nausithous caterpillars was not associated with ant density or plant density. This study suggests that the density of M. nausithous is limited by the density of the host ant M. rubra. We conclude that habitat management for M. nausithous should focus on the maintenance of habitats that hold both resources, but that enable high densities of M. rubra. In addition, it is discussed why high densities of host ants might be more important in predatory than in cuckoo-feeding Maculinea.     

Performance of Myrmica ant colonies is correlated with the presence of social parasites

1. The performance of ant colonies depends on different factors such as nest site, colony structure or the presence of pathogens and social parasites. Myrmica ants host various types of social parasites, including the larvae of Maculinea butterflies and Microdonmyrmicae (Schönrogge) hoverfly. How these social parasites affect host colony performance is still unexplored. 2. It was examined how the presence of Maculinea teleius Bergsträsser, Maculinea alcon (Denis & Schiffermüller), and M. myrmicae larvae, representing different feeding and growth strategies inside host colonies, is associated with worker survival, the number of foragers, and colony productivity parameters such as growth and reproduction. 3. It was found that the presence of social parasites is negatively associated with total colony production and the production of ant larvae and gynes. Male production was lower only in nests infested by M. teleius, whereas the number of worker pupae was significantly higher in all types of infested colonies than in uninfested colonies. Laboratory observations indicated that nests infested by Maculinea larvae are characterised by a higher number of foragers compared to uninfested nests but we did not find differences in worker survival among nest types. 4. The observed pattern of social parasite influence on colony productivity can be explained by the feeding strategies of parasitic larvae. The most negative effect was found for M. teleius, which feeds on the largest host brood and eliminates a high number of sexual forms. The strong, adverse influence of all studied parasite species on gyne production may result in low queen production in Myrmica populations exposed to these social parasites.     

Local populations of endangered Maculinea (Phengaris) butterflies are flood resistant

Semi-natural wet meadows are threatened by drainage, the abandonment of traditional management and climate change. The large blue butterflies Maculinea teleius and M. nausithous are flagship species associated with wet meadows and are the targets of many conservation programmes. However, there is little knowledge on the impact of natural catastrophes, such as floods, on the persistence of these butterflies. In our study we tested how a flood that resulted in the temporary inundation of meadows affected populations of M. teleius and M. nausithous. Studies were conducted in two consecutive seasons of 2009 (with ‘normal’ weather) and 2010 (with extreme rainfall and a consequent flood in May) in a wet meadow complex located in the Vistula River valley in southern Poland. In both years the abundance of adults was estimated for each local habitat patch (n = 55) within sympatric metapopulations of both species. Additionally, in June 2010, i.e. directly after the flood and shortly before the flight period, a total of 754 Myrmica ant nests in 10 habitat patches (6 inundated vs. 4 not inundated) were checked for the presence of Maculinea larvae and pupae. We found no impact of inundation on year-to-year changes in adult population sizes. The probability of occurrence of Maculinea larvae and pupae in ant nests was higher in temporarily inundated meadows. Our results indicate that temporary inundation occurring after long-term downpours does not negatively affect the investigated species even during the larval period in ant nests at ground level. This provides an argument against drainage works in wet meadows with Maculinea butterflies.     

Plant defences against ants provide a pathway to social parasitism in butterflies

Understanding the chemical cues and gene expressions that mediate herbivore–host-plant and parasite–host interactions can elucidate the ecological costs and benefits accruing to different partners in tight-knit community modules, and may reveal unexpected complexities. We investigated the exploitation of sequential hosts by the phytophagous–predaceous butterfly Maculinea arion, whose larvae initially feed on Origanum vulgare flowerheads before switching to parasitize Myrmica ant colonies for their main period of growth. Gravid female butterflies were attracted to Origanum plants that emitted high levels of the monoterpenoid volatile carvacrol, a condition that occurred when ants disturbed their roots: we also found that Origanum expressed four genes involved in monoterpene formation when ants were present, accompanied by a significant induction of jasmonates. When exposed to carvacrol, Myrmica workers upregulated five genes whose products bind and detoxify this biocide, and their colonies were more tolerant of it than other common ant genera, consistent with an observed ability to occupy the competitor-free spaces surrounding Origanum. A cost is potential colony destruction by Ma. arion, which in turn may benefit infested Origanum plants by relieving their roots of further damage. Our results suggest a new pathway, whereby social parasites can detect successive resources by employing plant volatiles to simultaneously select their initial plant food and a suitable sequential host.     

Specificity of an ant-lycaenid interaction

Summary Many lycaenid butterflies are believed to be mutualists of ants — the butterfly larvae secrete sugars and amino acids as rewards for the ants, and the ants protect the larvae from predation or parasitism. We examined the specificity of the relationship between the lycaenid Plebejus argus and ants in the genus Lasius. Eggs were not attractive to Lasius ants until the emerging larvae had broken through the chorion. First instar larvae were palpated and picked up by Lasius workers and taken to the nest. First instars were mostly ignored by Myrmica sabuleti ants and they were rarely detected by Formica fusca. Older larvae were more attractive to Lasius than to the other ant genera. Pupae were very attractive to Lasius, moderately so to Myrmica, and were ignored by Formica fusca. Teneral adults were palpated by Lasius, but were attacked by Myrmica and Formica workers. We conclude that P. argus is a specialist associate of Lasius ants. Two populations of Plebejus argus were compared: one is naturally associated with Lasius niger, and the other with Lasius alienus. In reciprocal trials, larvae were slightly more attractive to their natural host ant species. Since test larvae were reared on a single host plant species in captivity, this differentiation probably has a genetic basis.     

Myrmica ants host highly diverse parasitic communities: from social parasites to microbes

Myrmica ants have been model species for studies in a variety of disciplines, including insect physiology, chemical communication, ant social dynamics, ant population, community ecology, and ant interactions with other organisms. Species belonging to the genus Myrmica can be found in virtually every habitat within the temperate regions of the northern hemisphere and their biology and systematics have been thoroughly studied. These ants serve as hosts to highly diverse parasitic organisms from socially parasitic butterfly caterpillars to microbes, and many Myrmica species even evolved into parasitizing species of their own genus. These parasites have various impacts both on the individuals and on the social structure of their hosts, ranging from morphological malformations to reduction in colony fitness. A comprehensive review of the parasitic organisms supported by Myrmica and the effects of these organisms on individuals and on whole ant colonies has not yet been compiled. Here, we provide a review of the interactions of these organisms with Myrmica ants by discussing host and parasite functional, behavioral or physiological adaptations. In addition, for all “symbiont groups” of Myrmica ants described in this paper, we examine the present limitations of the knowledge at present of their impact on individuals and host colony fitness. In conclusion, we argue that Myrmica ants serve as remarkable resource for the evolution of a wide variety of associated organisms.     

Population ecology of the endangered butterflies Maculinea teleius and M. nausithous and the implications for conservation

Butterflies of the genus Maculinea are highly endangered in Europe. The cuckoo species M. rebeli has been thoroughly investigated through both empirical and modelling studies, but less is known about the population ecology of predatory Maculinea. We present the findings of a 2-year research study on sympatric populations of two endangered butterflies: Maculinea teleius and M. nausithous in the Kraków region, southern Poland. The study comprised mark–release–recapture sampling and laboratory rearing of butterflies from larvae collected in the field. For both species the sex ratio was slightly, but consistently, female-biased and there was little year-to-year change in the seasonal population sizes. Daily numbers showed greater variation between the 2 years of the study due to the differences in daily survival rate. The average life span of laboratory-raised butterflies kept in ideal conditions was more than 6 days, compared to only 2–3 days in the field. The recruitment of both males and females consistently followed a bimodal pattern. A small proportion of individuals (maximum 25%) changed sites, in spite of relatively short distances of ca. 100 m separating them. The results indicate that populations of both species are typically stable within their sites, possibly due to larval polymorphism, but there is little inter-site mobility and thus landscape corridors seem necessary to enhance metapopulation viability. A further problem to be considered in the conservation of Maculinea butterflies is the fact that their very short life span in relation to flight-period length reduces the effective population size.     

Mimetic host shifts in an endangered social parasite of ants

An emerging problem in conservation is whether listed morpho-species with broad distributions, yet specialized lifestyles, consist of more than one cryptic species or functionally distinct forms that have different ecological requirements. We describe extreme regional divergence within an iconic endangered butterfly, whose socially parasitic young stages use non-visual, non-tactile cues to infiltrate and supplant the brood in ant societies. Although indistinguishable morphologically or when using current mitochondrial and nuclear sequence-, or microsatellite data, Maculinea rebeli from Spain and southeast Poland exploit different Myrmica ant species and experience 100 per cent mortality with each other''s hosts. This reflects major differences in the hydrocarbons synthesized from each region by the larvae, which so closely mimic the recognition profiles of their respective hosts that nurse ants afford each parasite a social status above that of their own kin larvae. The two host ants occupy separate niches within grassland; thus, conservation management must differ in each region. Similar cryptic differentiation may be common, yet equally hard to detect, among the approximately 10 000 unstudied morpho-species of social parasite that are estimated to exist, many of which are Red Data Book listed.     

Local host ant specificity of Phengaris (Maculinea) teleius butterfly,an obligatory social parasite of Myrmica ants

1. Phengaris butterflies are obligatory social parasites of Myrmica ants. Early research suggested that there is a different Myrmica host species for each of the five European Phengaris social parasites, but more recent studies have shown that this was an oversimplification. 2. The pattern of host ant specificity within a Phengaris teleius metapopulation from southern Poland is reported. A combination of studying the frequency distribution of Phengaris occurrence and morphometrics on adult butterflies were used to test whether use of different host species is reflected in larval development. 3. Phengaris teleius larvae were found to survive in colonies of four Myrmica species: M. scabrinodis, M. rubra, M. ruginodis, and M. rugulosa. Myrmica scabrinodis was the most abundant species under the host plant but the percentage of infested nests was similar to other host ant species at two sites and lower in comparison to nests of M. rubra and M. ruginodis at the other two sites. Morphometric measurements of adult butterflies reared by wild colonies of M. scabrinodis and M. ruginodis showed that wing size and number of wing spots were slightly greater for adults eclosing from nests of M. ruginodis. 4. Our results suggest that P. teleius in the populations studied is less specialised than previously suggested. The results are consistent with the hypothesis that P. teleius is expected to be the least specific of the European Phengaris species, as it has the largest and best defended fourth‐instar caterpillars and, as a predatory species, it spends less time in the central larval chambers of the host colonies. The fact that individuals reared by M. ruginodis had wider hind wings may suggest that P. teleius had better access to resources in M. ruginodis than in M. scabrinodis colonies.