Unidentified blister beetle on Launea nudicaulis
I was thinking Chrysomelidae, Donacini tribe, maybe Plateumaris, but now upon further investigation I think perhaps a Lytta subgenus Poreopasta...? On Phacelia ciliata.
foto: Huatulco Parque National - Cruz del Monte
San Diego County, California, US
Many of them, chomping on the California Poppy petals.
Ash-gray Blister Beetle
Rice County, Minnesota
Blister beetles are beetles (Coleoptera) of the family Meloidae, so called for their defensive secretion of a blistering agent, cantharidin. There are approximately 7,500 known species worldwide. Many are conspicuous and some aposematically colored, announcing their toxicity to would-be predators.