Ladybugs are not shaped like cucumber beetles, this would be roundish or barely oval versus elongated. Re-state the overall shape. Also, was the dark spot the only spot, was half of the spot merged on each wing or was there an individual spot on each wing?

The pronotum stripe was stated well and could be a clue.

I mentioned cucumber beetles because other Gardenweb answers to "green ladybug" questions identified the insect as cucumber beetle.

The shape looked like this:

I copied this image from Google because the white spot/reflection on the image is in the same location as the dark hourglass spot of the insect I'm asking about. As best as I can remember, there were no other spots. Please note that the insect was moving very rapidly so the exact shape of the spot is questionable. Also, the green color was not iridescent. The overall length was about 3/8 in., but larger than the Asian lady beetles we have in east TN.

Hope this helps.

What you saw was likely a green stinkbug nymph, this would explain the roundish shape, ladybug+ size, yellow neck line, hourglass-like back spot, and scurrying but not flying when bothered. Try google images for green+stinkbug+nymph. The earlier-stage nymphs will be greener and have fewer markings.

Thanks!

Although none of the google pix resemble exactly what I saw, there is sufficient variation among the nymphs that I'll believe your answer.