From what I can make out in the picture, you do not have an insect, you have-CLICK>> Early Blight
It looks as though it's in it's early stages...
Early Blight fungus overwinters in plant residue and is soil-borne. It can also come in on transplants. Remove affected plants and thoroughly clean fall garden debris. Wet weather and stressed plants increase likelihood of attack. Copper and/or sulfur sprays can prevent further development of the fungus.