Not sure if I understand exactly how you're doing this, but I used butterflies in an eco before and it worked well. Their wings were basically a rectangle with a transparency map. (Noggin's butterflies from daz) which I loaded into the eco as objects. Anyhow, even if yours are different, just to check your material is still right  when in the eco, chose the material tab (see arrow) in the world browser and select the relevant material from the list of 'EcoSystem materials' , Edit the material and check the transparency map. You may need to invert the black/white by clicking the button the arrow points to, that's usually the reason behind this kind of behaviour.

"I paint that which comes from the imagination or from dreams, or from an unconscious drive. I photograph the things that I do not wish to paint, the things which already have an existence."
Man Ray, modernist painter
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