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Concept
Helicoverpa armigera
Summary
Helicoverpa armigera is a species of Lepidoptera in the family Noctuidae. It is known as the cotton bollworm, corn earworm, Old World (African) bollworm, or scarce bordered straw (the lattermost in the UK, where it is a migrant). The larvae feed on a wide range of plants, including many important cultivated crops. It is a major pest in cotton and one of the most polyphagous and cosmopolitan pest species. It should not be confused with the similarly named larva of the related species Helicoverpa zea.
This species comprises two sub-species: Helicoverpa armigera armigera is native and widespread in central and southern Europe, temperate Asia and Africa; Helicoverpa armigera conferta is native to Australia, and Oceania. The former sub-species has also recently been confirmed to have successfully invaded Brazil and has since spread across much of South America and reached the Caribbean. It is a migrant species, able to reach Scandinavia and other northern territories.
The cotton bollworm is very variable in both size and colour. The body length varies between with a wingspan of . The fore wings are yellowish to orange in females and greenish-gray in males, with a slightly darker transversal band in the distal third. The external transversal and submarginal lines and the reniform spot are diffused. The hind wings are a pale yellow with a narrow brown band at the external edge and a dark round spot in the middle.
The female cotton bollworm can lay several hundred eggs, distributed on various parts of the plant. Under favourable conditions, the eggs can hatch into larvae within three days and the whole lifecycle can be completed in just over a month.
The eggs are spherical and in diameter, and have a ribbed surface. They are white, later becoming greenish.
The larvae take 13 to 22 days to develop, reaching up to long in the sixth instar. Their colouring is variable, but mostly greenish and yellow to red-brown. The head is yellow with several spots. Three dark stripes extend along the dorsal side and one yellow light stripe is situated under the spiracles on the lateral side.
Official source
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Related concepts (3)
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Bt cotton is a genetically modified pest resistant plant cotton variety that produces an insecticide to combat bollworm. Strains of the bacterium Bacillus thuringiensis produce over 200 different Bt toxins, each harmful to different insects. Most notably, Bt toxins are insecticidal to the larvae of moths and butterflies, beetles, cotton bollworms and flies but are harmless to other forms of life. The gene coding for Bt toxin has been inserted into cotton as a transgene, causing it to produce this natural insecticide in its tissues.
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Bacillus thuringiensis
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