Ohio designated the ladybug as the official state insect. in 1975. The ladybug is actually a ladybird beetle, and is also called lady beetle, ladybird, or ladyfly. There are more than 450 species of ladybug in North America and Ohio designates no specific one. According to the Ohio General Assembly's resolution, :

"The ladybug is symbolic of the people of Ohio—she is proud and friendly, bringing delight to millions of children when she alights on their hand or arm to display her multi-colored wings, and she is extremely industrious and hardy, able to live under the most adverse conditions and yet retain her beauty and charm, while at the same time being of inestimable value to nature."

Ladybird beetles exist in all of Ohio's eighty-eight counties. Most ladybugs assist Ohio's farmers and gardeners as ferocious predators eating small pests such as aphids. New York, Massachusetts, New Hampshire, Tennessee, and Delaware also designate the ladybug as their state bug or insect.

Source:

Ohio's State Insect - Ladybug: Ohio History Central

Links:

State Insects - 50 States List