I think my plan backfired on me

My son has a tendency to be afraid of bugs, following his sisters in their hysteria. I have never been afraid of bugs and am always trying to get them more comfortable with bugs. Apparently, we are going to have to go bug by bug for this. I now have the girls in love with doodle bugs (AKA rolly pollies) and fairly comfortable around bees, ants, gnats, flies, and spiders. Hannah actually is very fascinated with spiders and has been spying on a little spider in a window for a few days. We are still struggling with stink bugs and a few others though.
Well, they were introduced to a new bug recently. June bugs are not something we have seen in Germany or New York. Thanks to my mom's lovely introduction to them as having "sticky legs" the girls are terrified of them. Isaac missed out on that intro, and so I started him off with a dead one. I came up with a plan on the spot and while the girls were in the deep end of the pool with my mom. I had him hold a dead June bug. Then I told him how funny it would be to scare the girls and Mimi with the bug. I told him to take it over and say he had something to show Mimi and show her the bug. I prepared him that she would scream and that he could throw it in the air. I told him it would be so funny.
When he did it and they all started screaming, he threw it and joined them in their high-pitched shrills. It kind of backfired a bit. He still looked like a big wuss. I was hoping to try to counteract the screams by explaining to him that it was funny, but my first attempt failed. I will not give up though. This boy will not be a weanie. I am determined. It's not over yet.