NO! Ok, so I don't have any proof that they're poisonous, but I was a bug nerd as a kid (still am) and our yard was infested with these. I once caught whole assortment of bugs and put them in a jar. One of the bugs was a daddy long legs (it didn't occur to me at the time that spiders eat other bugs). That daddy long legs systematically went around that jar and bit and killed every bug in it, except for the boxelder bugs. Another time, I put one in a venus fly trap and the whole uh...trappy part (?), turned black. After about a week, I opened it up and the bug was still alive.