If you didn't eat the bug, you don't have much of a case. Food companies are very skeptical about claims of bugs, mouse heads, fingers, etc. in their food because of all the well-publicized fake claims that have been made recently. You might be better off contacting the company by letter, telling them what happened, tell them you are very upset and want compensation. They might offer you a small settlement. Whatever they offer, you should seriously consider taking it. Meanwhile be sure to save the can, the greens and the bug. The can has important information about when and where it was made and the source of the greens.
Keep in mind, that greens are a farm product, and a bug is a natural kind of thing to find in greens. We don't like it, but Federal law permits a certain amount of bug parts in food because to some degree it is unavoidable.
I hope this helps.
Lawyer
26 years litigating important insurance and injury cases; well-known legal author