Twenty-spotted Lady Beetle

P. vigintimaculata is about 1.75–3.0 mm in length, lives 1-2 years, and has four or five distinctive dark spots on the pronotum in an "M" shape. The elytra have dark, orange or bicolored spots on a white background. Although it is sometimes confused with the fourteen-spotted lady beetle (Propylea quatuordecimpunctata) and the Asian lady beetle (Harmonia axyridis), its unique pattern helps to distinguish it from other lady beetle species found in North America.

In a laboratory setting, the subspecies P. vigintimaculata taedata undergoes four larval instars, molting and then pupation. The timing of life cycle varies according to rearing conditions.

Instars and pupation. The first instar larvae has a white oval body with small hairs projecting from the thorax. The larvae of the second instar have a stripe and a much darker color that gradually turns lighter with each subsequent instar. During the end of the fourth instar, the larva attaches itself to a leaf or a petiole to molt. Pupae emerge with wing pads as well as black spots.

Duration. When eggs were deposited in 20°C it took about 32 days for adults to emerge. At 25°C it took about 20 days.