''Listrodromus nycthemerus'', the holly blue Darwin wasp, is a species of ichneumon wasp belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Ichneumonidae The Ichneumonidae, also known as ichneumon wasps, ichneumonid wasps, ichneumonids, or Darwin wasps, 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 ...

. This species is a

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

, its sole host species being the

holly blue The holly blue (''Celastrina argiolus'') Retrieved April 20, 2018. is a butterfly that belongs to the lycaenids or blues family and is native to the Palearctic. Description The holly blue has pale silver-blue wings spotted with pale ivory dots ...

butterfly (''Celastrina argiolus'').

Taxonomy

''Listrodromus nycthemerus'' was first formally described as ''Ichneumon nycthemerus'' by the German zoologist

Johann Ludwig Christian Gravenhorst Johann Ludwig Christian Carl Gravenhorst (14 November 1777 – 14 January 1857), sometimes Jean Louis Charles or Carl, was a German entomologist, herpetologist, and zoologist. Life Gravenhorst was born in Braunschweig. His early interest in inse ...

from

Piedmont Piedmont ( ; ; ) is one of the 20 regions of Italy, located in the northwest Italy, Northwest of the country. It borders the Liguria region to the south, the Lombardy and Emilia-Romagna regions to the east, and the Aosta Valley region to the ...

. This species was classified in the new genus '' Listrodromus'' in 1845 by

Constantin Wesmael Constantin Wesmael (4 October 1798, in City of Brussels, Brussels – 26 October 1872, near to Saint-Josse-ten-Noode) was a Belgians, Belgian entomologist. Life Of modest origin, he was granted a bursary to study law. He taught, initially, ...

, this species being the type species of that genus. Traditionally the genus was included in the

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

Listrodromini within the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

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

but is now classified within tribe Ichneumonini.

Description

''Listrodromus nycthemerus'' is a very small wasp which is predominantly black and yellow. This species has a body length of .

Distribution

''Listrodromus nycthemerus'' has been recorded from Europe where records come from Ireland, Great Britain, Netherlands, France, Spain, Germany, southern Norway, southern Sweden, southern Finland, Croatia and Austria.

Life cycle

''Listrodromus nycthemerus'' is a parasitoid of the holly blue, and has no other known host. The wasp lays an egg on a first

instar An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...

caterpillar of the holly blue, inserting the egg into the caterpillar's body and the adult wasp emerges from the chrysalis, killing the chrysalis before its emergence. The population of the butterfly is tracked by that of the wasp, when holly blue populations are low the wasp population falls and this allows the butterfly population to increase and the population of ''L. nycthemerus'' can increase as there are more hosts available to be parasitised. The wasp population takes 6 or 7 years to reach its peak and at its peak as many as 99% of the holly blue caterpillars will be host to a larval wasp, causing the host population to crash.

References

{{Taxonbar, from=Q2592393 Ichneumoninae Insects described in 1820