The ladybug was adopted as the official state bug or insect symbol of Massachusetts thanks to a campaign that began in 1974 by a second-grade class in the town of Franklin (The Ladybug Story).

Ladybugs help gardeners and farmers by eating tiny insect pests that damage plants. A ladybug can consume up to 60 aphids per day, and will also eat a variety of other harmful insects and larvae (including scales, mealy bugs, leaf hoppers, mites, and other types of soft-bodied insects), as well as pollen and nectar. Ohio, New York, New Hampshire, Tennessee, and Delaware also designate the ladybug as an official state symbol (see list of state insects for all 50 states).

Also called lady beetle, ladybird, or ladyfly, the most common variety of ladybug found in Massachusetts is the two-spotted lady beetle (Adalia bipunctata). According to John Losey, a Cornell University entomologist who leads the Lost Ladybug Project. (a project funded by a National Science Foundation grant recruiting citizen scientists, particularly children, to search for nine-spotted ladybug and other ladybug species and send photos of them to Cornell for identification and inclusion in a database), there are about 5,000 species of ladybugs, also known as ladybird beetles, with about 450 species in the United States.

Source:

Massachusetts State Symbols: Citizen Information Service
The Ladybug Story: Massachusetts Secretary of State
Ladybug, Ladybug, Where Have You Gone? - msnbc

Links:

State Insects - 50 States List