Aren't there boy butterflies too?
The gender identification thing is a combination of "nature and nurture." My boy's preferences in activities and clothing and characters is based around what they see. So they like comic book characters because that's what Daddy likes. Grandpa and I love puzzles. Not just the usual kid puzzles but the big jigsaw puzzles, so The Boy loves them and will sit for long periods of time working on them. Both children love letters, numbers, and colors. Meatball counts up to 10 and will go further if you say "11."
We haven't necessarily said that certain things are for boys and certain things are for girls. Meatball doesn't care what color the little ball popper toy is at the play center we frequent (there is one that is blue with rainbow popping balls and one that is pink with pastel popping balls), as long as he gets one. The kids love their play kitchen and "cook" just like I do. It was a gift from a friend whose very burly sons had one from their sister--they played with it to the dismay of their father and grew up to be chefs.
They don't play a lot of dressup, although their clothes are pretty boyish. I don't doubt that both of them would pick a pink or purple shirt if they could, every now and then, because they like all colors. Knowing The Boy, he would want to see all colors represented in his wardrobe because he is a completist like his daddy.
So, regarding the butterflies, last night at the JCC we went to a family Shabbat dinner. Since Purim is coming up, they also had a few Purim activities, including a collection of costumes. The Boy was interested in the butterfly wings. And I guess boys aren't supposed to like butterflies? A few other kids were talking about him, saying "that's the BOY who wants to be a butterfly" and giggling about it. Fortunately they said nothing directly to him.
About the wings themselves: they were fabric on wire, about two feet high, and they were black, brown, and orange. These were not fairy princess wings--these were the kind of wings that would make a kid think he could jump off of something and fly. The Boy has seen butterflies and he has seen both boys and girls (and big purple dinosaurs) pretend to be them. Butterflies are cool--why wouldn't a kid want to pretend to be one?
Not sure what to make of this, other than to let him be a butterfly if he darned well wants to. And to refrain from telling those boys that the cow masks that they were wearing are way more girly than a set of realistic butterfly wings, given than cows are well-known for their lactation abilities.