Insect specimen colour change over time (prevention)

[Beatsy]

I've bought a sweep net so I can collect loads of insects during the summer, freeze them, then thaw, set and air-dry the best specimens for photographing through the winter months (with some proportion done at the time of course).

However, looking into a container of hawthorn shield bugs I collected last autumn I was very surprised at the degree of colour change they suffered in a few short months (see attached pics). They were stored in small, wide-mouthed plastic screw-top containers after freezing, re-thawing and air drying.

I can't say I've ever noticed this much "degradation" in dried specimens before. Is it unusual or does this always happen (perhaps only to certain species)? Pinned insect collections seem to keep their colours for decades, or more. I suspect keeping my catches in the freezer until they're needed would avoid this but I'd prefer to store dried specimens I've sorted and set (a bunch at a time) so they are "ready to go" for photography when the inclination strikes.

Note: I may keep some specimens longer than a year but I don't want a pinned insect collection per-se. Just medium term storage for photography. Any suggestions/hints gratefully received.

Stored bug as it is now (February)


Bug from the same batch photographed last September

[rjlittlefield]

Unfortunately pigment green does tend to fade badly.

I don't know any solution for this problem.

I will be interested to hear, if somebody else does.

--Rik

[Ichthyophthirius]

Hi,

Some pigments fade; reds are also problematic. Dragonflies in particular loose their colours very quickly. Structural colours (interference colours) usually keep well.

Sometimes the body contents liquify and spoil the specimen, especially with larger insects, as they don't dry outfast enough.

Ladybird (Coccinellidae) red pigments keep better after brief treatment with sulphur dioxide gas.

Regards, Ichty

[Lou Jost]

Even some structural colors are fugitive because they depend on tissue spacing maintained by liquids. Golden tortoise beetles (Chrysomelidae) are good examples. They even change color at will while they are still alive!
https://en.wikipedia.org/wiki/Golden_tortoise_beetle