Cotton leafworm, Cotton worm
Alabama argillacea, the cotton leafworm or cotton worm, is a moth of the family Erebidae. It is native to the New World, but has been extirpated from the United States and Canada, having not been recorded since 1998. In the Neotropics, it can be found from Mexico to northern Argentina. The larva is considered a pest of cotton. They feed on the leaves, twigs, and buds.
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TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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starts withThe adult moth has light brown to orange wings. It wingspan varies from 25 to 35 mm. The larvae are up to 40 mm long, green or brownish with black and white stripes. They have a characteristic pattern of black dots on each segment.
Alabama argillacea is a specialist feeder on Gossypieae, which includes cotton and its close relatives. Like other anomine erebids, its distribution is primarily tropical and only migrates north in the summer and fall under favorable conditions. Its eggs are sensitive and cannot tolerate any amount of frost in the winter, restricting the adults to historically spend the winter in Florida and Texas. However, its eggs may have never overwintered at all in the United States. Any adults which found themselves up north in the fall would have died by the first frost. Females lay an average of 400 eggs, which is unusually high for a noctuoid.
The entirety of the damage done to cotton is done by the larvae. Young instars feed primarily the underside of the leaves, skeletonizing them as they feed. Older instars move vertically and feed on the younger, fresher foliage near the bolls and sometimes on the bolls themselves. Depending on latitude, two to eight generations could have occurred in the United States each year. This made them an especially dangerous pest, as they fed year-round in some locations. In especially bad years, the larvae destroyed over a third of cotton crops. This resulted in the United States losing almost $30 million a year in lost profits (over $700 million in today's terms). Adults feed at flowers of many different species, but are probably not significant pollinators. Being a migratory species, the population of Alabama argillacea varied drastically from year-to-year and even location-to-location. No reliable records of A. argillacea exist from before 1793. The largest outbreaks occurred in 1804, 1825, 1846, 1868, and 1873, with intervening years having very minimal damage.
Much effort went into predicting when and where the caterpillars would strike next, but this research generated very little in terms of accurate predicting tools. When it struck, the destruction was nothing short of complete. In a letter to The American Agriculturalist in September 1846, farmer Thomas Affleck gave the following account of the destruction of A. argillacea:
