It looks a bit like a Lightning Bug but don’t be fooled. This is a Margined Blister Beetle (Epicauta funebris), which can be found in North America east of the Great Plains.  There are three color forms of this beetle, black, ash-gray, and margined as seen here.

They exude a substance called cantharidin if disturbed, which causes blisters when in contact with skin or mucous membranes. Cantharidin is highly toxic when consumed by chickens and horses, even in small amounts, and can cause death.

In the vegetable garden they can be a pest, causing damage to flowers and leaves of eggplants, potatoes, tomatoes, and beets.