Heliothis zea

Helicoverpa zea, commonly known as the corn earworm, is a species (formerly in the genus Heliothis) in the family Noctuidae. The larva of the moth Helicoverpa zea is a major agricultural pest. Since it is polyphagous (feeds on many different plants) during the larval stage, the species has been given many different common names, including the cotton bollworm and the tomato fruitworm. It also consumes a wide variety of other crops. The species is widely distributed across the Americas with the exception of northern Canada and Alaska. It has become resistant to many pesticides, but can be controlled with integrated pest management techniques including deep ploughing, trap crops, chemical control using mineral oil, and biological controls. The species migrates seasonally, at night, and can be carried downwind up to 400 km. Pupae can make use of diapause to wait out adverse environmental conditions, especially at high latitudes and in drought. The corn earworm is found in temperate and tropical regions of North America, with the exception of northern Canada and Alaska as it cannot overwinter in these areas. Helicoverpa zea found in the eastern United States also does not overwinter successfully. They live in Kansas, Ohio, Virginia, and southern New Jersey, but survival rate is mainly affected by the severity of the winter. Corn earworm moths regularly migrate from southern regions to northern regions depending on winter conditions. They are also found in Hawaii, the Caribbean islands, and most of South America, including Peru, Argentina, and Brazil. Cotton earworms have also been reported from China in 2002. The taxonomy of Helicoverpa was poorly understood for a long time. Many older works referring to 'Heliothis obsoleta', a synonym of H. armigera, are actually about H. zea. Eggs are individually deposited on leaf hairs and corn silks (not in reference given). The eggs are initially pale green in color, but over time they turn yellowish and then grey. Eggs are 0.5 mm in height and average about 0.55 mm in diameter. They hatch after 66 to 72 hours of development. Once larvae have breached the chorion, they spend up to 85% of their time emerging from their shell. In this eclosion process, the larvae work to make the exit hole larger than their heads. Larvae spend the rest of the time making a silk meshwork around the exit hole; this both helps them escape the shell and helps them find the shell afterwards so they can feed on it. After feeding on their shell, larvae rest about 3 minutes before they begin feeding on the plant material around them. Following hatching, larvae feed on the reproductive structures of the plant and usually develop through four to six instars. Initially, the young larva feed together, and this stage is their most destructive stage. Through maturation, older larvae become aggressive and cannibalistic, leaving one or two larvae per feeding site (See Interfamilial Predation). They usually have orange heads, black thorax plates, and a body color that is primarily black. Their bodies can also be brown, pink, green, and yellow with many thorny microspines. Mature larvae migrate to the soil, where they pupate for 12 to 16 days.