Xyloryctes thestalus, and Chrysina gloriosa. But I had them in rubber containers maybe it's not noticeable on soil. I gave them water which they say you don't have to do. Could that have possibly been the culprit? We have very hard water in Az hence the white? But it's not like they all died at once.
I gave xyloryctes thestalus water because they would walk through,and push the little things of maple syrup around and I could see it ball up on them. So I thought they would good if they cleaned off which seemed too work.
