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Life Cycle
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 life cycle can be completed in just over a month. The eggs are spherical, 0.4 to 0.6 mm in diameter and have a costate surface. They are white, later becoming greenish.
The larva takes 13 to 22 days to develop, reaching up to 40 mm in length 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 centimeters (1.6–3.9 in), or in cotton bolls or maize ears.
Adult moth wingspan is 30-45 mm. The forewings are brownish or reddish-brown (females) or dull greenish to yellow or light brown (males). Hind wings are pale with a broad, dark outer margin. H. armigera moths have a pale patch near the centre of this dark region. Moths feed on nectar and live for around 10 days. Females lay around 1000 eggs in singles or clusters on growing points, leaves, flower buds, flowers and developing fruits, and sometimes on stems. Moths tend to lay eggs on the top third of healthy plants and on vigorously growing terminals.
