Adult Lygus lineolaris are true bugs that can grow up to 6.5 mm in length and are variable in colour; generally they are brown with yellow, orange or red accents, but their colouring can range from pale yellow with few dark accents to almost completely black with yellow markings. Adults that have overwintered are typically darker than summer adults. Regardless of colour, all lygus bugs have a light-coloured “V” shape on their dorsum (back).
Lygus bugs overwinter under plant debris, such as dead weeds, leaf litter and tree bark, and become active in early spring. They begin to feed on developing plant buds and shoots immediately, migrating into crops throughout the spring and into summer. As they feed, they lay their eggs on crop stems and, if the weather is warm enough, can produce up to three generations per year.
The eggs of Lygus lineolaris are about 1 mm long, shaped like a thin, slightly-curved flask, truncated with a flat cap from which the nymph emerges. The adults insert their eggs into the host plant tissue with only this cap exposed. Small (1 mm) yellowish-green, wingless nymphs emerge from the eggs 7–10 days later and begin to feed alongside the adults.They go through five nymphal stages, and as they mature they develop dark spots on the thorax and abdomen as well as wingpads. The lygus bug completes its life cycle in three to four weeks.