Rhinocyllus conicus

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Rhinocyllus conicus
Rhinocyllus conicus dorsal.jpg
Dorsal view of Rhinocyllus conicus
Rhinocyllus conicus lateral.jpg
Lateral view of Rhinocyllus conicus
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Curculionidae
Genus: Rhinocyllus
Species:
R. conicus
Binomial name
Rhinocyllus conicus
(Frölich, 1792)
Synonyms
  • Curculio conicusFroelich, 1792
  • Curculio thaumaturgusRossi, 1794

Rhinocyllus conicus is a species of true weevil. It is best known as a controversial agent of biological pest control which has been used against noxious thistles in the genera Carduus , Cirsium , Onopordum , and Silybum .

The adult weevil is black and covered in a thin black and yellowish mottled coat of hairs. It is a short-snouted beetle up to 6 millimeters in total body length. The female lays over 100 eggs on or near the bracts of the thistle flower head. She covers the eggs with masticated plant tissue to protect them from predators. When the white larva emerges from its egg it burrows into the flower head and feeds on the flower parts and developing seeds. As it grows it deposits frass and chewed plant tissue on the walls of its chamber, producing a rigid protective shell in which it will pupate. Pupation takes up to two weeks and when the weevil emerges as an adult it remains inside the chamber for a few more weeks before tunneling out of the plant.

Damage to the plant occurs mainly from larval destruction of the flower head, which prevents seed production. Some larvae tunnel through the upper stem instead of chambering in a flower head; this can also be destructive to the plant. Adults do some damage as well when they feed on the foliage. Thistles which reproduce only via seed, such as musk thistle, are controlled well by this weevil and its seed head destroying larvae. Some thistles are able to reproduce vegetatively, and while they are impacted as well, they can sometimes survive.

This weevil is native to Eurasia and North Africa. It was first introduced to the United States for thistle biocontrol in 1969, and it is now widely established in that country. The weevil was found to be very effective in reducing the spread of invasive thistles, particularly musk thistle, but also welted, Italian, bull, milk, and other thistles. However, the weevil will also readily attack native thistles of genus Cirsium, [1] in some cases contributing to population decline. [2] It is for this reason that this weevil is no longer recommended for distribution as a biocontrol agent. Further releases of the weevil are prohibited in many areas.

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<i>Cirsium arvense</i> Species of flowering plant

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<i>Bangasternus fausti</i> Species of beetle

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<i>Cyphocleonus achates</i> Species of beetle

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<i>Larinus obtusus</i> Species of beetle

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<i>Metzneria paucipunctella</i> Species of moth

Metzneria paucipunctella is a species of moth known as the spotted knapweed seed head moth. It is used as an agent of biological pest control against noxious knapweeds, particularly spotted knapweed.

Chaetorellia australis is a species of tephritid fruit fly known as the yellow starthistle peacock fly. It is used as an agent of biological pest control against the noxious weed yellow starthistle.

<i>Eustenopus villosus</i> Species of beetle

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<i>Larinus curtus</i> Species of beetle

Larinus curtus is a species of true weevil known as the yellow starthistle flower weevil. It is native to Southern Italy, Southern Europe, the Middle East and the Caucasuses. It is used as an agent of biological pest control against the noxious weed yellow starthistle in the United States.

<i>Cirsium undulatum</i> Species of thistle

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<i>Larinus planus</i> Species of beetle

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<i>Trichosirocalus horridus</i> Species of beetle

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<i>Cirsium vinaceum</i> Species of thistle

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<i>Hylobius transversovittatus</i> Species of beetle

Hylobius transversovittatus is a species of weevil in the family Curculionidae. It is native to the Old World where both adults and larvae feed on purple loosestrife. This plant is regarded as an invasive species in North America and the weevil has been introduced into both the United States and Canada in an effort to control the plant.

<i>Galerucella calmariensis</i> Species of beetle

Galerucella calmariensis is a species of leaf beetle in the family Chrysomelidae. It is commonly known as the black-margined loosestrife beetle and is native to Europe and Asia where both adults and larvae feed on purple loosestrife. It has been introduced in North America as a biological control agent for purple loosestrife.

References

  1. Louda, S. M., D. Kendall, J. Connor, and D. Simberloff. 1997. Ecological effects of an insect introduced for the biological control of weeds. Science 277: 1088-1090.
  2. Rose, K. E., S. M. Louda, and M. Rees. 2005. Demographic and evolutionary impacts of native and invasive insect herbivores: a case study with Platte thistle, Cirsium canescens. Ecology 86: 453-465.