Hello,
For now 4 species that I have reared has developed black dots as they reached the middle of their final instar.
These have not caused any deaths in my rearings, but they are annoying when it comes to takkng picture of them.
It's not a parasite, and it doesn't affect the moths as the moths that emerged last time, with the same problem (A. Ningpoana fed on Juglans) did not change from healthy specimens (males ~11cm, females ~14cm). I did only have a single crippled specimen over 13 cocoons.
It happened with this previously mentioned species, but also with Saturnia pyri on Fraxinus, Sphinx ligustri and Rothschildia lebeau on Ligustrum, and also Actias luna on Juglans. Last year I did not have this problem with my first luna rearing, but this year I had.
People I sent eggs to doesn't seem to have that problem, I recieved eggs of ningpoana from another brood to pair them with my brood, both broods had the same problem, however, the guy who sent me the eggs did not have that problem... And still doesn't
I am thinking that maybe it is due to an excessive pollution, did anyone have this problem? I am searching for answers 
Thanks a lot if you try to help me!
Thomas.