What bug is this?
Thank you for the question and good photo of insect and damage. These insects are fourlined plant bugs. They feed on many ornamental plants by using piercing sucking mouth parts to feed leaving behind the characteristic marks you see on your plant. Generally, the damage is cosmetic and nothing need be done but sometimes the plant is badly damaged or killed. Many people are noticing that the damage this year is particularly bad. It's important to clean up all the dead plant material in the fall so that the eggs aren't left to overwinter causing new grief next year.
Read about control methods here: http://www.extension.umn.edu/garden/insects/find/fourlined-plant-bugs/
Thank you for contacting Extension.