''Ichneumon eumerus'' is a species of parasitic wasp belonging to the family

Ichneumonidae The Ichneumonidae, also known as the ichneumon wasps, Darwin wasps, or ichneumonids, are a family of parasitoid wasps of the insect order Hymenoptera. They are one of the most diverse groups within the Hymenoptera with roughly 25,000 species cu ...

, subfamily

Ichneumoninae Ichneumoninae is a worldwide subfamily of the parasitic wasp family Ichneumonidae. Ichneumoninae are koinobiont or idiobiont endoparasitoids of Lepidoptera. It is the second largest subfamily of Ichneumonidae, with 373 genera. Ichneumonines ...

. It is a specialist parasite of the larva of the mountain Alcon blue butterfly (''

Phengaris rebeli ''Phengaris rebeli'' (formerly ''Maculinea rebeli''), common name mountain Alcon blue, is a species of butterfly in the family Lycaenidae. It was first found and described in Styria, Austria, on Mount Hochschwab around 1700. Although it was init ...

'').

Life cycle

The life cycle of ''I. eumerus'' is dependent on a butterfly, the mountain Alcon blue (''Phengaris rebeli''), the larvae of which trick ants in the species ''

Myrmica schencki ''Myrmica schencki'' is a species of ant in the genus ''Myrmica''. Distribution and habitat ''Myrmica schencki'' is distributed across Europe (from Great Britain, Sweden, Finland in the North to Spain, Italy and the Balkans in the South), the Ca ...

'' into carrying the larvae into their nest and caring for them as if they were ant larvae. The adult female wasp seeks out a nest of these ants; it seems to be able to tell by smell whether there are larvae of the butterfly present in the nest and if there are, it attempts to enter. The ants attack the intruder, but the wasp produces a

pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

that causes the ants to become confused and attack each other. This gives the wasp the chance to search out the butterfly larvae and lay an egg in each one. Afterwards the ants continue to feed and look after the butterfly larvae which in due course pupate. The wasp eggs hatch and the wasp larvae feed on the butterfly larvae from the inside, eventually pupating inside the butterfly pupae.

Status

The mountain Alcon blue butterfly is a rare species which is known from the northern part of Portugal, the western Pyrenees, France, Switzerland, part of Germany and Greece at altitudes between . The butterfly is considered to be a "

vulnerable species A vulnerable species is a species which has been categorized by the International Union for Conservation of Nature as being threatened with extinction unless the circumstances that are threatening its survival and reproduction improve. Vulne ...

", and the wasp, being entirely dependent on the butterfly, would become extinct if the butterfly were to die out.

References

{{Taxonbar, from=Q1656397 Ichneumoninae Insects described in 1857 Hymenoptera of Europe