Plutus opal butterflies and black cocktail ants

April 16, 2023
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Plutus opal Chrysoritis plutus

Chrysoritis plutus, the Plutus opal, is a butterfly of the family Lycaenidae found only in South Africa.

The wingspan is 24–28 mm for males and 26–35 mm for females. Flight period is two broods from August to December and January to April.

  • Woodhall, Steve (2005). Field Guide to Butterflies of South Africa. Cape Town, South Africa: Struik. ISBN 978-1-86872-724-7.

Larvae feed on the Thesium species. Thesium is a genus of flowering plants in the family Santalaceae, sandalwoods, a widely distributed family of flowering plants (including small trees, shrubs, perennial herbs, and epiphytic climbers) which, like other members of Santalales, are partially parasitic on other plants. Its flowers are bisexual or, by abortion (“flower drop”), unisexual. Modern treatments of the Santalaceae include the family Viscaceae (mistletoes), previously considered distinct.

They are associated with Crematogaster peringueyi, a southern African arboreal species of ant also known as the black cocktail ant or swartwipgatmier (Afrikaans) for their colour and habit of arching their abdomens when alarmed.

The ants make their nests in old Protea flowers, dead, hollow branches, and under tree bark, also making nests constructed of well-chewed vegetable matter with the consistency of papier-mâché. The outer walls of these nests are blackened by the salivary secretions, and are thin, with the interior divided into irregular, connected cells, like a coarse sponge. These more or less spherical nests, ranging in diameter from 10–30 cm, are built in a fork or among the branches, some of the branches passing through the nest. Workers are glossy black and 3–5 mm long, and the larger queen is about 8 mm long, both having heart-shaped abdomens.

Symbiosis

Butterflies belonging to the family Lycaenidae, like the Common Opal (Chrysoritis thysbe), Dickson’s Copper (Chrysoritis dicksoni) and other members of this genus, have a mutualistic relationship with various species of Crematogaster.

The Lycaenidae and Crematogaster spp. are strongly associated with the fynbos growing in the Natal Drakensberg, and on Table Mountain Sandstone in the western and southern Cape. C. peringueyi also occurs at Jagersfontein, De Aar, Willowmore, Clanwilliam, Garies, Springbok, and Laingsburg.

Various honeydew-producing insects such as aphids, scale insects and mealybugs are diligently protected by the ants. Common Opal larvae also produce honeydew from a gland on the back, leading to their being constantly guarded from predators such as parasitic wasps. The larvae at first feed and rest among the young leaves of the foodplant, but with the 3rd instar move to the plant’s base. Here the ants extend their protection and hospitality by constructing papery daytime shelters for the larvae which feed by night on plants such as Bietou, and species of Aspalathus, Osteospermum and Zygophyllum. The larvae use these same shelters for pupating, the pupae also producing honeydew to ensure ant protection.

Pheromone alarms are common among the social Hymenoptera. Some of these have been chemically identified, but the number is still small compared with the large number of species making use of them. The ketone octan-3-one is seen as the major component of the pheromone complex secreted from the heads of C. peringueyi.

The sting or venom gland of other ant species has evolved in C. peringueyi into a gland secreting a smelly and irritant fluid, which, together with the ant’s painful bite, is a strong deterrent to predation or attack.

Interactions with humans

C. peringueyi – and other ants with a similar location and lifestyle, Linepithema humile and Formica perpilosa – are indirect pests of South African viticulture. Addison & Samways 2000 and Mgocheki & Addison 2009 find that these ants interfere with the natural biological control of Planococcus ficus provided by various natural enemies. The ants and the mealybug have a pre-existing mutualistic (honeydew) relationship and so provide them with a refuge.  In their next work Mgocheki & Addison 2010 find that managing the ants did indeed lead to increased parasitism on the mealybug and decreased crop injury.

General

Stages of development & nest of Crematogaster peringueyi. “The Study of Ants” – S. H. Skaife (Longmans 1961) Clockwise from top left: Worker, queen, alarmed worker, nest, pupa, larva, eggs

The genus of Crematogaster, created by Peter Wilhelm Lund in 1831 (Lettre sur les habitudes de quelques fourmis du Brésil, adressée a M. Audouin. Annales des Sciences Naturelles 23: 113-138) is diverse, widespread and abundant, distributed over tropical, subtropical and warm-temperate regions throughout the world. Greek: ‘kremastos’ + ‘gaster’ = ‘suspended stomach’, which would make the literal generic spelling ‘Cremastogaster’, but Lund set it as ‘Crematogaster’, which is preserved by priority.

The Whistling Thorn (Acacia drepanolobium) A mouthful of that could change your perspective. This species of acacia grows two kinds of thorns. The main defense is provided by pairs 5cm long arranged nearly at a right angle. Smaller stipular spines grow between the pairs of big thorns. These emerge from hollow galls, bulbous swellings 2 to 3cm across. One of four different species of ant lives in each of these igloos, which they open up by cutting holes into them. A dying bush whistles as the wind blows over these entrances. Most acacias make toxins that it rushes to leaves that are under attack by browsers. The whistling thorn doesn’t. It is infested with stinging ants that swarm out and prepare to bite anything they can when the branch is disturbed. Most browsers seem to avoid infested bushes, perhaps because the ants stink of formic acid.

The whistling thorn of East Africa is fiercely protected by at least three species of Crematogaster which occupy the swollen thorns and, in exchange for nectar from the tree, vigorously attack browsers.

Trail-laying amongst cocktail ants involves shuffling their hind legs without touching of the soil with their abdomens, as is common with other ant species. This results in a setting of footprints for other foragers to follow. The hind leg’s tendon to the claw is swollen where it passes through the tibia into a spindle-shaped reservoir containing the pheromone, an oil-like, relatively nonvolatile substance.

Synonyms

  • Cremastogaster peringueyi Emery

Publications

  • Emery, C. 1895i. Voyage de M. E. Simon dans l’Afrique australe (janvier-avril 1893). 3e mémoire. Formicides. Ann. Soc. Entomol. Fr. 64: 15-56 (page 27, figs. 16, 17 worker, queen, male described)
  • Emery, C. 1922c. Hymenoptera. Fam. Formicidae. Subfam. Myrmicinae. [part]. Genera Insectorum 174B: 95-206 (page 148, Combination in C. (Acrocoelia))
  • Crewe, R.M., Brand, J.M., and Fletcher, D.J.C. 1969. Identification of an alarm pheromone in the ant Crematogaster peringueyi. Ann. Entomol. Soc. Am. 62:1212.

References

  1. Edge, D.A. & Terblanche, R.F. 2020. Chrysoritis plutus (amended version of 2020 assessment). The IUCN Red List of Threatened Species 2020: e.T161338093A175072325. https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T161338093A175072325.en. Downloaded on 08 August 2021.
  2. Chrysoritis at Markku Savela’s Lepidoptera and Some Other Life Forms
  3. Woodhall, Steve (2005). Field Guide to Butterflies of South Africa. Cape Town, South Africa: Struik. ISBN 978-1-86872-724-7.
  4. Hewson & George [et al.], Santalaceae taxonomy Archived 2015-03-24 at the Wayback Machine, 1984, pp. 191-194.
  5. Pilger, R. Santalaceae (with 17 figures). R. Br. Prodr. Fl. Nov. Holl. (1810) 350, pp. 1-45.
  6. jferrer (28 July 2012). “Ants inside a King Protea”. iSpot (southern Africa).
  7. “Guide to the insect species of Southern Africa – Cocktail Ants, Genus Crematogaster”. Eco Travel Africa. Archived from the original on 2013-07-08.
  8. “Identification of an Alarm Pheromone in the Ant Crematogaster peringueyi“. Researchgate.net. Retrieved 18 March 2022.
  9. https://en.wikipedia.org/wiki/Vachellia_drepanolobium
  10. “Lepidopterists Society of Africa”. Lepsoc.org.za. Archived from the original on 2013-04-21. Retrieved 18 March 2022.
  11. Woodhall, Steve (2005). Field Guide to the Butterflies of South Africa – Steve Woodhall. p. 236. ISBN 9781868727247. Retrieved 18 March 2022.
  12. “Crematogaster peringueyi” (PDF). Metamorphosis. 21, 3: 122–5. September 2010. Retrieved 18 March 2022.
  13. “Module 9 – predation and competition”. Archived from the original on 2013-04-22. Retrieved 2013-01-20.
  14. Bostanian, Noubar J.; Vincent, Charles; Isaacs, Rufus (26 June 2012). Arthropod Management in Vineyards : Pests, Approaches, and Future Directions. Dordrecht. pp. xvi+505. ISBN 978-94-007-4032-7. OCLC 798568502. ISBN 978-94-007-4031-0. ISBN 978-94-007-9436-8.
  15. “Ohio State University”. Archived from the original on 2016-03-04. Retrieved 2013-01-21.
  16. Leuthold, R. H. (18 March 1968). “A Tibial Gland Scent-Trail and Trail-Laying Behavior in the Ant Crematogaster Ashmeadi Mayr”. Psyche. 75 (3): 233–248. doi:10.1155/1968/73761.

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