Blister beetles feed gregariously on tomatoes, potatoes, beans, peas and many other vegetable crops. They are ash gray or striped to blackish. When crushed, they release a substance that can easily blister skin. Care and gloves are needed to handpick beetles off plants into a bucket of soapy water. Blister beetles generally move on after a few days.
https://hnr.k-state.edu/extension/info-center/common-pest-problems/common-pest-problem-new/Blister%20Beetles%20.pdf
https://hnr.k-state.edu/extension/info-center/common-pest-problems/common-pest-problem-new/Blister%20Beetles%20.pdf