Please refer to EC 86-1545, Common Forage Legume Insects , for color photos of alfalfa weevil larvae, adult, and damage. The insect usually overwinters as an adult in protected areas outside of fields, such as windbreaks, wooded areas, or other protective habitats. Some eggs are laid in the fall, but most are deposited in the spring when weevils re-enter fields. The female weevil chews a hole into the alfalfa stem and deposits a mass of two to 25 eggs. The average female weevil is capable of laying from 500 to 2,000 eggs during her lifetime.
Young larvae molt or shed their skins three times, increasing in size at each molt.
After feeding is complete, most mature larvae move to leaves near the base of the plant or to debris on the soil surface where they form loosely woven cocoons of silk and bits of plants. The larvae then transform to the pupal stage, from which the adults emerge in about 10-14 days. The body is light brown after emergence, with a darker brown stripe on the back extending from the front of the head to about half the length of the body. These markings vary somewhat with the age of the insects and may become less obvious as body scales are rubbed off and the color darkens. Adult weevils remain in the field for a few weeks until they move out to spend the summer in nearby protective areas.