Blue-green stains on yellow Pierids

[indra]

Occasionally I get some small blue-green stains on some yellow Pierid butterflies after placing them in a relaxing chamber. There seems to be no way to remove them. I use common tap water which does contain chlorine and some copper. Has anyone else seen this, and does anyone have any idea what is actually causing it and how tp prevent it from happening?

[Paul K]

I noticed some of those stains on my P.rapae collected in Calgary this summer. I relaxed it same way as hundreds of other white butterflies and never noticed anything like that. I guess if that would be copper dissolved in water problem we would see those green stains more often, but indeed it is interesting why this happened.
Also I am not chemists but i think only HO2 is actually evaporating and soaks specimens in the chamber and any metals should stay on the bottom unless the specimen has direct contact with water drops.

[trehopr1]

If at all possible always try to pin any Pieridae you collect as quickly and as fresh as possible. Avoid placement in any relaxing chamber unless it is only for a few short hours. I have noticed this peculiarity about Pieridae for some time so I make it a point to spread them quick. I believe it is the very tiny water droplets themselves which form on the wings in the relaxer which are the culprit. Somehow, the chemical(s) producing the whites and yellows in Pierid scales is sensitive to these tiny water droplets (resting or accumulating) on the scales too long. The chemicals basically leach into the water droplets creating little green spots or "freckling".
When one deals with papered Pieridae it's always a toss-up as to weather you will get a truly good clean example. Also, you have probably noticed that Pieridae as a group seem to exude a lot more "wing-staining" fluids from their abdomens; as compared with other families of butterflies. Extra care and diligence in preparation is the key I believe to having success in acquiring nice specimens of this family.

[nomihoudai]

Too much humidity causes these. It's a reaction in the wing. Mount them fresh if possible or use as little water as possible.