If I combine all the previous answers, I come to the following hypothesis: larva develops in dungmass - larva pupates - heavy rain soaks remaining dung mass surrounding teneral beetle - drops of liquid dung attach to teneral beetle - liquid dung dries on hardening beetle - beetle emerges with dung spots attached to exoskeleton - beetle gets collected by one of us.
Here in Brazil this is also pretty common on top of Dichotomius
and Ontherus species.
I always thought this would just be "dirt".
On 10/11/2017 6:32 PM, JF Mate wrote:
Yes, I have also seen such defects on Copris,
Onitis and some aphodines in Spain, usually in wet conditions
(Spring). In dry specimens the defects become darker and
generally match the colour of the surrounding exoskeleton. I
have always assumed it was due to the integument failing to
properly sclerotize due to water saturation during emergence.
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