Heliothis armigera

The cotton bollworm, corn earworm, or Old World (African) bollworm (Helicoverpa armigera) (also known as the scarce bordered straw in the UK, where it is a migrant) is a moth, the larvae of which 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, related species Helicoverpa zea. This species comprises two sub-species: Helicoverpa armigera armigera is widespread in central and southern Europe, temperate Asia and Africa; Helicoverpa armigera conferta is found in 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 12 and 20 millimetres (0.47 and 0.79 in) with a wingspan of 30–40 millimetres (1.2–1.6 in). 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 0.4 to 0.6 mm 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 40 mm 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. The ventral parts of the larvae are pale. They are rather aggressive, occasionally carnivorous and may even cannibalise each other. If disturbed, they fall from the plant and curl up on the ground. The pupae develop inside a silken cocoon over 10 to 15 days in soil at a depth of 4–10 centimetres (1.6–3.9 in), or in cotton bolls or maize ears. The cotton bollworm is a highly polyphagous species. The most important crop hosts are tomato, cotton, pigeon pea, chickpea, rice, sorghum, and cowpea. Other hosts include groundnut, okra, peas, field beans, soybeans, lucerne, Phaseolus spp., other Leguminosae, tobacco, potatoes, maize, flax, Dianthus, Rosa, Pelargonium, Chrysanthemum, Lavandula angustifolia, a number of fruit trees, forest trees, and a range of vegetable crops. In Russia and adjacent countries, the larvae populate more than 120 plant species, favouring Solanum, Datura, Hyoscyamus, Atriplex, and Amaranthus genera.