Chrysochus Asclepiadeus

''Chrysochus asclepiadeus'' (or ''Eumolpus asclepiadeus'') is a member of the leaf beetle subfamily Eumolpinae. It is considered the type species of the genus '' Chrysochus'', though it has sometimes been placed within the genus ''Eumolpus''. It is the only species of ''Chrysochus'' distributed in the western Palaearctic. It is mainly found in Europe, though it is also known from Kazakhstan and Turkey in Asia.

Taxonomic history

The species was first described by Peter Simon Pallas, who gave it the scientific name ''Chrysomela asclepiadea'' in 1773. The species epithet, ''aescelpiadea'' (or ''asclepiadeus''), is named after the milkweed genus ''Asclepias'', one of the species' food plants. The species was later twice described again under two separate names: Guillaume-Antoine Olivier named it ''Cryptocephalus cyaneus'' in 1791 (from the Latin , meaning "dark blue"), while Johan Christian Fabricius named it ''Chrysomela praetiosa'' in 1792. The latter was sometimes spelled "''pretiosa''", derived from the Latin ("valuable, precious").

In 1798, the genus ''Eumolpus'' was first established in Johann Karl Wilhelm Illiger's ''Verzeichniß der Käfer Preußens'', including ''C. praetiosa'' as well as other species. Fabricius also included ''C. praetiosa'' in the same genus in 1801. In 1836, ''C. praetiosa'' was transferred again to the genus '' Chrysochus'', which was first established by Louis Alexandre Auguste Chevrolat in Dejean's ''Catalogue des Coléoptères''. ''Chrysomela praetiosa'' was then designated as the type species of the genus by Sylvain Auguste de Marseul in 1864. It was later discovered that ''Chrysomela praetiosa'' was a junior synonym of ''Chrysomela asclepiadea'', changing the valid scientific name for the species to ''Chrysochus asclepiadeus''.

In 1993, Warchałowski used the combination "''Eumolpus asclepiadeus''" for the species, based on Jacquelin du Val's work from 1868 where ''Chrysochus'' was considered a synonym of ''Eumolpus''. He also designated ''E. praetiosus'' as the type species of ''Eumolpus'', stating that the species of ''Chrysochus'' must be included in the genus. Some European entomologists followed Warchałowski, while others continued to use ''Chrysochus'' as valid. Warchałowski's type designation for ''Eumolpus'' was invalid, since Latreille had designated ''Eumolpus vitis'' as the type species in 1810, which placed ''Bromius'' in synonymy with ''Eumolpus''. This threatened stability for ''Eumolpus'', ''Bromius'' and ''Chrysochus''. In 2010, an application was made to the International Commission on Zoological Nomenclature to conserve the three genus names by suppressing the name ''Eumolpus'' Illiger, 1798. This was accepted by ICZN in 2012.

Subspecies

In recent literature, ''Chrysochus asclepiadeus'' is usually listed as including two subspecies, ''Chrysochus asclepiadeus asclepiadeus'' and ''Chrysochus asclepiadeus asiaeminoris''. The nominate subspecies, ''C. a. asclepiadeus'', has a wide distribution range in Europe, while ''C. a. asiaeminoris'' is known only from Babadağ, Denizli in southwestern Turkey (its type locality) and has not been reported since its description in 1948. In 2015, Ekiz ''et al.'' found that the two subspecies are not geographically distinct and are morphologically very similar, and concluded that ''C. a. asiaeminoris'' is actually a synonym of the nominate subspecies.

Description

''C. asclepiadeus'' has a dark blue body with a purplish metallic reflection. Adult males have an average length of 9.3 mm and an average width of 4.9 mm. Adult females are generally similar to males, but larger; they have an average length of 10.2 mm and average width of 5.4 mm.

Biology

When disturbed, ''C. asclepiadeus'' releases a defensive secretion from glands on the protonum and elytra. The main components of this secretion are phenylalanine, tryptophane, leucine and diacetyl putrescine. Unlike the secretions of North American species ''Chrysochus auratus'' and '' Chrysochus cobaltinus'', the secretion of ''C. asclepiadeus'' does not contain cardenolides.

Distribution

''C. asclepiadeus'' is distributed in Armenia, Austria, Azerbaijan, Croatia, the Czech Republic, France, Germany, Greece, Hungary, Italy, Kazakhstan, Moldavia, Montenegro, North Macedonia, Poland, Russia (Southern European Territory), Serbia, Slovakia, Switzerland, Turkey and Ukraine.

Gallery

Eumolpus asclepiadeus Pallas, 1776.jpg
Eumolpus.asclepiadeus.-.calwer.45.06.jpg

References

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Eumolpinae
Beetles of Europe
Beetles of Asia
Taxa named by Peter Simon Pallas
Beetles described in 1773