I have a pot of dianthus in my garden. They are covered with this black and yellow flying beetle and have no blossoms. 3-4 have ventured over to my spaghetti squash vine. Are these helpful on pest control or not? I've never seen them before but it's also the first year I moved the dianthus into the garden.

Welcome to NGA. Without any idea where you are, the answer is rather generalized. A location, State/country etc helps greatly in correct IDs for bugs plants and pests.

It appears to be a Harlequin stink bug.

http://goodlifegarden.ucdavis....