Chrysolina coerulans
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Infraorder: Cucujiformia
Family: Chrysomelidae
Genus: Chrysolina
Subgenus: Synerga
Species:
C. coerulans
Binomial name
Chrysolina coerulans
(Scriba, 1791)
Synonyms[1]

Chrysomela coerulans L.G.Scriba, 1791

Chrysolina coerulans, also known as the blue mint beetle or blue mint leaf beetle, is a species of beetle in the family Chrysomelidae. It is in the subgenus of Synerga. It is native to a wide range of countries between mid and eastern Europe and lives alongside rivers and in meadows, it feeds on various plant members of the mint family.

It was first spotted in the UK in 2011, when it was first reported to the Royal Horticultural Society’s entomology department in July. In 2012, it was found breeding in Kent, Cambridgeshire and Lincolnshire. It has further spread throughout the UK.

Description

Chrysolina coerulans
Chrysolina coerulans

The larvae of Chrysolina caerulans are soft-bodied, rounded in shape and black in colour.[2]

Th adult beetles are 6–10 mm (0.24–0.39 in) long,[3][4][5] with black legs and antennae. It has a smooth head, without longitudinal groove,[3] and parallel-sided thorax.[6] The pronotal disk (which is found at the top of the first thoracic segment) of C. coerulans has fine punctures.[6] It has a smooth elytra (hardened forewing),[3] which is distinctly metallic blue,[6] or iridescent blue.[2]

These beetles should not be confused with the 'green mint beetle' (or Chrysolina herbacea), as it is greener in appearance (emerald green,[4]) and slightly larger in size,[2] as C. herbacea measures 7–11 mm in length.[7] C. herbacea and Chrysolina graminis (tansy beetle) both have a mixture of fine and coarse punctures on the pronotal disk.[6]

Similar to other species of Chrysolina beetles, C. coerulans has cardiac glycosides (including xylose) in its defensive glands.[8]

Taxonomy

It is commonly known as the blue mint beetle,[1][5][9] or blue mint leaf beetle.[10]

It was originally published and described by German theologian and entomologist, Ludwig Gottlieb Scriba in 1791 in 'Journal für die Liebhaber der Entomologie' (Journal Liebh. Ent.), Volume 3 on page 286.[11][12]

Its species name coerulans is a form of the Latin noun caeruleus meaning 'turning blue',[13] or coeruleus meaning 'blue'.[5] Occasionally, it is misspelt as Chrysolina caerulans, (with an 'a' in the second name).[3][6][14]

Distribution

Its distribution spans mid and eastern Europe,[5][10] including Cyprus,[15] Hungary,[16] France, Italy, Macedonia, Turkey.[11] Then in 2009; Latvia,[17] and then in 2011; Austria, Belarus, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Estonia, Germany, Ireland, Liechtenstein, Poland, Romania, Slovakia, Slovenia, Switzerland, the Netherlands, and Ukraine.[6] The 2009 source also mentions the range extending to Central Asia; the Caucasus, Iran, Iraq, Afghanistan, southern Urals, western China, northern and eastern India.[17]

Habitat

It is found in damp meadows and along riversides,[10] in lowlands and mountains, up to 1,650 m (5,410 ft) above sea level.[12]

Biology

Chrysolina coerulans

Adults can be found from May to September. Their life span is one year,[10] and they are diurnal (meaning active during the day),[2] They feed on various plant species of Mentha and Tanacetum,[12] including within a garden setting; garden mint, Moroccan mint, spearmint and Corsican mint types,[2] as well as the wild horse mint.[15] Both larvae and adults feed on mint leaves in spring and summer.[5][10][18]

Blue mint beetle in the UK

In Kent,[2] it was detected breeding in the UK for the first time in July 2011,[5][9][10] it had come from mainland Europe.[10] It was then first reported to the Royal Horticultural Society's entomology department.[4]

The RHS then started asking gardeners to check mint plants for tell-tale holes, then report them back to them.[4][18] There had been a single confirmed sighting, the RHS was keen to find out if it was an isolated outbreak.[4]

RHS plant health principal scientist Andrew Halstead said as the bug was established on mainland Europe, "The detection of breeding adults in the UK could mean problems for gardeners who grow this herb," he said. "It is important that we find out if there are other breeding adults in the UK."[4]

Main symptoms UK gardeners were asked to look for irregular holes in foliage and blue beetles on the leaves.[9][10]

In 2012, it was recorded as being found in several locations in Cambridgeshire and Lincolnshire.[5][6][9]

It was later recorded as being found in Hampshire, parts of London and Edinburgh. It was expected to spread further throughout the UK,[2][5][9] as the beetle has a widespread occurrence on the mainland of Europe.[4]

There are a few other beetles that are similar in form to the blue mint beetle, but they feed on different plants. A metallic blue beetle located near an Alder tree will most likely be an alder leaf beetle (Agelastica alni), as opposed to a blue mint beetle found on mint plants.[2]

Treatment

Biological treatment

Mint plants are quite hardy and are able to tolerate some damage to the leaves. However, hand removal of beetles can be done if required.

Chemical treatment

As mint plants are normally grown to be used for culinary purposes, it is recommended that chemical treatments should not be used. Also pesticides should be avoided if plants are located near water bodies.

If needed, there is a wide range of organic pesticides on the market. These can be applied to the larvae over a course of several applications. However, as chemicals are non-selective, they can affect everything nearby.[2]

References

  1. 1 2 "Chrysolina coerulans (Scriba, 1791)". www.gbif.org. Global Biodiversity Information Facility. Retrieved 3 May 2021.
  2. 1 2 3 4 5 6 7 8 9 "Blue Mint Beetle Chrysolina coerulans". candide gardening.com. Archived from the original on 3 August 2020. Retrieved 9 May 2020.
  3. 1 2 3 4 "Chrysolina herbacea (Linnaeus, 1758)". uk beetles. Retrieved 7 May 2020.
  4. 1 2 3 4 5 6 7 Rosenberg, Marc (20 August 2012). "Watch out for blue mint beetle". amateurgardening.com. Retrieved 7 May 2020.
  5. 1 2 3 4 5 6 7 8 Dr. Peter Jarvis The Pelagic Dictionary of Natural History of the British Isles: Descriptions (2020), p. 312, at Google Books
  6. 1 2 3 4 5 6 7 Salisbury, Andrew; Malumphy, Chris; Halstead, Andrew J. (2012). "First record of blue mint beetle Chrysolina coerulans (Scriba, 1791) (Chrysomelidae) breeding in Britain". The Coleopterist. 21 (1): 35–37. Retrieved 3 May 2021.
  7. ↑ "Chrysolina herbacea (Duftschmid, 1825)". Coleoptera.org. Archived from the original on 2023-01-24. Retrieved 2017-03-27.
  8. ↑ E. David Morgan Biosynthesis in Insects (2004), p. 112, at Google Books
  9. 1 2 3 4 5 "Blue mint beetle". rhs.org.uk. Retrieved 20 April 2017.
  10. 1 2 3 4 5 6 7 8 "Blue Mint Leaf Beetles - Chrysolina coerulans - UK Safari". www.uksafari.com. Retrieved 7 May 2020.
  11. 1 2 Blagoĭ Gruev Checklist of Eumolpinae, Chrysomelinae, Alticinae, Hispinae and Cassidinae (Coleoptera: Chrysomelidae) In Republic of Macedonia (1998), p. 2, at Google Books
  12. 1 2 3 Blagoĭ Gruev and Vassil Tomov Catalogus Faunae Bulgaricae Coleoptera: Chrysomelidae (1998), p. 48, at Google Books
  13. ↑ "The Names of Plants, David Gledhill". 28 August 2014. Retrieved 8 May 2020.
  14. ↑ "coerulans Scriba, 1791 described in Chrysomela". Retrieved 3 May 2021.
  15. 1 2 George P. Georghiou, Benaki Phytopathological Institute, 1977 The Insects and Mites of Cyprus: With Emphasis on Species of Economic Importance to Agriculture, Forestry, Man, and Domestic Animals, p. 46, at Google Books
  16. ↑ Pierre Jolivet, Jorge A. Santiago-Blay and Michael Schmitt (Editors) Research on Chrysomelidae: Volume 2 (2009), p. 243, at Google Books
  17. 1 2 Bukejs, Andris (January 2009). "Two new leaf-beetles species (Coleoptera: Chrysomelidae) for the Latvian fauna". Baltic Journal of Coleopterology. 9 (2): 155–160.
  18. 1 2 "RHS Wisley. Blue mint beetle". www.bbc.co.uk. Gardener's World. Retrieved 3 May 2021.

Other sources

  • Cambridge Scientific Abstracts, (2000). Entomology Abstracts, Volume 31, Issues 7-9
  • Salisbury, A. & Halstead, A.J. (2012). Blue mint beetle Chrysolina coerulans (Scriba) (Chrysomelidae) breeding in Cambridgeshire. The Coleopterist 21(3): 145.
  • Sage, B. (2009). Chrysolina coerulans (Scriba) (Chrysomelidae) in Norfolk: the second British record. The Coleopterist 18(1): 6.
  • Sage, B. (2009). The second occurrence of Chrysolina coerulans (Scriba) (Chrysomelidae) in Norfolk. The Coleopterist 18(2): 138.
  • Recently found Chrysolina coerulans in village of Dearham, Cumbria in May 2022. Photographed.
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