Projects with Phengaris butterflies, other social parasites,
and (mostly butterfly) conservation

David Nash, Centre for Social Evolution


I have several possibilities for bachelor or speciale projects available to Copenhagen University students in 2020-21. Most of these will involve either previously collected data or fieldwork with Danish populations of the Alcon blue butterfly Phengaris (formerly Maculinea) alcon (ensianblåfuglen) or Swedish populations of P. alcon and Danish and Swedish populations of P. arion (sortplettetblåfuglen) and related species, butterfly conservation in general, and projects about other social parasites (The microgyne form of the ant Myrmica rubra, and the socially parasitic leaf-cutting ant Acromyrmex insinuator).

I plan to organize field trips to Læsø, Jutland and Møn (and possibly Skåne) in 2020, to survey and/or collect Phengaris butterflies and Myrmica ants, although whether these will be possible under the current COVID-19 restrictions remains unclear. I am always interested in volunteers (who will normally have to be students or employees at Copenhagen university) to help out on these field-trips, and I can normally cover all travel and food for the period of the trip. It is also possible to join or leave one of the trips part-way through, but that will mean using public transport to get to or from the field. Please contact me if you are interested:             

To find out more about the research group and the researchers involved, please see the CSE web site under the "Social Parasitism" theme, e-mail me ( or come to talk with me in person.

1) Chemical manipulation of ants by metalmark butterflies?

Bachelor thesis project


Metalmark butterflies are mainly distributed in the Neotropics. The caterpillars of the Irenea Metalmark (Thisbe irenea) are tended by Ectatomma ants. The caterpillar feeds on leaf-tissue and nectar from the antprotected plant Croton billbergianus, thus exploiting a plant-ant mutualism. The caterpillar may use a complex communication strategy to subvert the ants' chemical communication and gain access to resources and protection. This study will examine aspects of the butterfly-plant-ant interaction through chemical analyses. The chemical infiltration strategy of the Irenea Metalmark caterpillars will be examined by comparison of cuticular hydrocarbon profiles among the caterpillars and with their host ants.

We are looking for a bachelor student who wants to analyse the chemical data in order to gain insight into the caterpillar's interspecific communication, and thus allow us to assess the costs and benefits for the interacting species in this symbiosis.

If you want to find outmore about the project please contact David Nash (

Time: The data is already collected, so it could be carried out at any time.

Projects with the Alcon blue butterfly

Life cycle of the Alcon blue butterfly:






Larvae 1+2
Larvae 2
Larvae 2+3
Eggs (viable)
Egg shells

Caterpillars of P. alcon spend the winter and spring inside nests of Myrmica red ants, where they eat the ant brood, and are fed on regurgitated food by the worker ants. From around the beginning of June, some of the larvae pupate (still inside the nest), while others seem to wait for another 12 months before doing so. The pupal stage lasts around a month, after which the adult butterflies emerge from the ant nest (they are covered in very loose scales, which protect them against marauding ants on their way out of the nest, and do not expand their wings until they are out in the open air). The adults live a few days, feeding on flower nectar, and mate. The females lay their eggs on the unopened flower buds of the marsh gentian Gentiana pneumonanthe (klokkeensian), and the first instar caterpillars hatch through the base of the eggs directly into the developing flowers, where they eat the ovaries. After about 2 weeks, and having gone though three moults, the fourth instar larva emerges from the flower bud and lets itself down to the ground on a silken thread. Here it waits to be discovered by a Myrmica ant, which will pick it up and take it back to the ant nest, where it will complete its development.




Most of our fieldwork has been carried out on Læsø, where the university used to have two field stations conveniently situated close to the two major populations of P. alcon on the island. Unfortunately, most of our research is now limited to the sourthern part of the island, as most of the northern part was sold, along with the field stations, to a private owner in 2014, and he has not allowed access to these sites since. There are also several populations of P. alcon on Jutland, mostly on the west coast. In addition, there are populations of P. alcon in Skåne, just beyond Malmö and near to Göteborg. P. arion is only found on Møn in Denmark, but there are also some populations in central and western Skåne and on Öland and Gottland, as well as in other Baltic countries (Finland, Estonia).

Potential projects 2020-21

My main research focuses on questions of the evolution of parasitism in Phengaris butterflies and their coevolution with their ant hosts, including the evolution of host specificity. All of these fields are highly relevant for conservation of Phengaris butterflies, and I have become increasingly interested in insect conservation in general.

In 2020 we had planned to carry out quite a bit of fieldwork, including carrying out our annual surveys of the butterfly populations on Læsø during the flight period and while eggs are visible on the food plants. Volunteers are welcome for such work. In addition there are several projects that we hope to carry out this year or in the near future which could form the basis of Bachelor or Speciale projects. While I have listed some potential projects and questions that I am interested in answering below, these are mostly for guidance, as I prefer to develop tailor-made projects for each student to combine his or her interests with what is feasible. This means that there will almost certainly be other projects available which will develop during the year. Please contact me about particular project ideas.

If you are interested, please contact David Nash (

2) The status of Phengaris alcon and Phengaris rebeli in Denmark - a comparison over more than 50 years

More than 50 years ago Svend Kaaber published an intriguing paper about the variation in wing patterns of Phengaris butterflies in Denmark, in which he showed that there was a gradient in characters that had been associated with Phengaris alcon and Phengaris rebeli in Danish populations (Kaaber 1964). Since then, the status of Phengaris rebeli as a species has become far from clear, although some of the morphological features of this butterflty as originally described from Austria, do seem to be present in Danish Phengaris, but not in Phengaris alcon from other regions. Kaaber kept good records of where specimens were collected, and still has most of them in his private collection (with others being in the museum collections in Copenhagen and Aarhus. Hence, in 2017, in collaboration with Svend and Thomas Simonsen from the Natural History Museum in Aarhus, I intend to both re-visit the sites from which he collected, and to re-analyze the specimens collected more than 50 years ago. Both morphology (based on wing patterns) and DNA (microsatellites) will be compared, which will allow us to answer several different questions:

  1. How has genetic and morphological diversity changed over more than 50 years?
  2. Do morphological and genetic variation and distinctness correlate with each other?
  3. How do Danish specimens with the characteristics of Phengaris rebeli compare with the type specimens of this (sub)species, both genetically and morphologically?
  4. Are Danish specimens of Phengaris more variable compared with those from other parts of Europe?

I hope that this project can form the basis of a couple of Speciale projects, and several bachelor projects.

Kaaber, S. (1964) Studies on Maculinea alcon (Schiff.) -rebeli (Hir.) (Lep. Lycaenidae) with Reference to the Taxonomy, Distribution, and Phylogeny of the Group. Entomologiske Meddelelser 32, 277-319.

Time period of field work: June - August; Time period for lab work - any time of year.
Current status (2020): All museum DNA samples have now been collected, but have not been sequenced yet. Some field samples were collected from Læsø in 2018 and Jutland in 2019, but more samples from Jutland are needed.

3) Projects with Phengaris alcon butterflies on Aage V. Jensen's fond reserves

The alcon blue butterfly (Phengaris alcon) has a complex life cycle where it depends on a specific host plant, the marsh gentian (Gentiana pneumonanthe) for its early development, and then spends most of its life inside nests of red ants (Myrmica sp.). The alcon blue has declined considerably in Denmark over the last century, mostly due to habitat changes that affect its host plants and ants, and it is now listed as vulnerable on the Danish red list. Three Aage V. Jensen’s fund reserves used to support populations of the Alcon blue – Lille Vildmøse, Filsø and Råbjerg møse, but it disappeared from Lille Vildmøse in the 1950s, and its status on the other reserves is unknown. Several possible projects are available to:

  1. Assess the current distribution and status of the alcon blue, its food plant and possible host ants on these reserves.
  2. Compare populations of the alcon blue on these reserves with well-known populations on Læsø and in other parts of Jutland in terms of population genetics and host ant specificity.
  3. Compare populations of Myrmica ants on the reserves with those elsewhere in terms of social structure and population genetics.
  4. To assess changes in the host plant and ant populations, and their likely effect on possible reintroduction of the alcon blue as a result of reestablishment of wetlands in Lille Vildmøse and Filsø.

Time period for field work: Between May and September.

4) Possible sites for expansion/reintroduction of Phengaris arion in Denmark

Phengaris arion is currently only found on a single site in Denmark, on the island of Møn, but used to be much more widespread. The reason for its decline is still not entirely clear, but land use chanes on many sites have meant that the niches of its two hosts (the host plant Thymus sp., and host ant Myrmica sabuleti) no longer overlap sufficiently on many former sites. This project aims initially to map the distribution of these hosts on both former sites that might be considered for reintroduction, and new sites that may be suitable for management for the butterfly. In particular we would like to examine the distribution of host (and non-host) ants on several sites, both in the former range, and close to the remaining site on Møn.

Time period for field work: Between May and September.

5) Has there been any loss of genetic diversity in Phengaris alcon populations over the last 15/100 years?

In 2005 we collected samples of M. alcon from various sites in Jutland and on Læsø, and compared them with samples that were collected in 1995 as part of a project looking at variation in allozymes, and which had been kept frozen ever since. When we analyzed both sets of samples, we found that there had been an apparent 40% loss in genetic diversity between 1995 and 2005. However, since the samples had been sampled and stored in different ways, we could not rule out that this was an artefact of different handling of the samples. Hence we collected sample from some of the same populations again in 2017, 2018 and 2019, and plan to compare these with the 1995 and 2005 samples, to determine whether there has been a similar loss in diversity in this second period.

Time period of field work: August; Time period for lab work September - December
Current status (2020): Samples have beeen collected, and most sequencing carried out within a beachelor project. Some collection of additional samples, and/or re-analysis of the sequence data in 2020 could form the basis of another project.

6) The biodiversity of obligate myrmecophiles (projects in collaboration with Aage V. Jensen's fond reserves)

Larger colonies of many ant species have beetles, fly-larvae and spiders living in obligate symbiosis in the ant nests. Most of these are rare and little studied, so their distribution patterns in Denmark are very poorly known. We also normally do not know whether they are parasites, commensals or even mutualists. As we know from other insects that are obligatorily associated with ants (e.g. Phengaris butterflies), ant myrmecophiles tend to have very interesting forms of chemical mimicry or chemical ‘invisibility’ to avoid being recognized by the ants. Projects of this kind are suitable for BSc projects involving several students, and such projects could then be a starting platform for MSc work on cuticular hydrocarbon chemistry. Depending on the taxonomic groups, co-supervision by entomology curators at the Zoological Museum will be possible.

Time period for field work: Spring - Autumn

7) Effect of the life history of Phengaris butterflies on their population and conservation genetics

This project would involve the development and running of mathematical models of the Phengaris life cycle with explicit genetic structure, to examine the effect of potential bottlenecks caused by the unusual life history of Phengaris buttrflies on genetic diversity and genetic drift.

This is a computer based project that can be carried out at any time of year.

8) Genetics of Phengaris species (several projects)

We have major on-going projects involving the genetics of Phengaris alcon and Phengaris arion in Denmark and Sweden. These are based on an extensive set of microstellite markers developed over the last few years. There will almost certainly be small projects available related to this, for example, based around extracting DNA from egg-shells, to avoid harming the existing populations, and using genetic fingerprinting to examine the behavioural ecology of Phengaris alcon.

Particuar questions we would like to answer are:

These projects could involve both fieldwork and labwork based on previously collected samples

9) Why are some Myrmica ant colonies more susceptible to Phengaris social parasitism than others?

The goal of this project is to find out whether within colony relatedness of Myrmica ants affects adoption time of caterpillars of Phengaris alcon. It involves collection of ant colonies and Phengaris caterpillars on Læsø and adoption experiments and lab work at CSE.

Time period for field and lab work: August – September

Projects with other butterflies

10) Comparison of morphology, breeding and immunocompetence of lycaenid butterflies with different levels and types of myrmecophily

Many butterflies in the family lycaenidae associate with ants (myrmecophily), and this can range from mutualistic associations, in which the caterpillars of the butterflies gain preotection from ants in exchange for nutritious secretions, to parasitic associations (like that of Phengaris), where the caterpillars feed on the ant larvae inside the ant nest. The variety of interactions are also expected to be associated with life history differences. Among the ideas that we want to test are:

Comparative work could use museum speciemns, plus specimens collected in the field.

Time period for field and lab work: All year round

11) Projects on conservation of Danish butterflies

Phengaris butterflies represent two of the butterfly species of European concern in Denmark, but there have also been reductions in the numbers of and extinctions of several other butterfly species in Denmark over the last century. The last few years has seen an increase in activities associated with butterfly conservation in Denmark, but we still lack quite a lot of basic information about butterfly distributions and abundances. We have several potential projects involving either field surveys or working with published and unpublished distribution data.

Time period for field work: May – September
Time period for literature work: All year round

Projects with ants

Projects with Myrmica rubra microgynes

Myrmica rubra produces queens of two sizes - "normal" queens (macrogynes) and miniature quuens (microgynes) that are about the same size as workers. These microgynes seem to have evolved multiple times as social parasites of nests headed by macrogynes, and provide a clear example of ongoing sympatric speciation. I have an ongoing project to investigate such microgynes and relate their distribution to differences in social organization of Myrmica rubra populations (which can vary tremendously in queen numbers). I have several potential projects, both field- and lab-based on this system, including:

Time period for field work: May – September
Time period for lab work: All year round

15) Is Myrmica lonae a good species?

The red ant Myrmica lonae was originally described in 1926, but ever since its status as a good sepcies has been controversial, as it is very difficult (but possible) to separate from Myrmica sabuleti based on Morphology (Seifert XXX), but not based on mitochondrial haplotypes (Ebsen et al. 2019). Thsi project aims to carry out both morphometric analysis and DNA sequencing (both nuclear and mitochondrial) on the same, selected, specimens of M. lonae and M. sabuleti across Europe to try to clarify the status of M. lonae. This is important for conservation, as M. lonae, if a true species, is rarher rare, and is also a host for the rare butterfly Phengaris arion (Tartally et al. 2019), and the social parasite, Myrmica hirsuta (Radchecncko & Elmes 2010), in Northern Europe.

Last modified: Thursday April 23, 2020